The War in Abkhazia was fought between Georgian government forces for the most part and Abkhaz separatist forces, Russian government armed forces and North Caucasian militants between 1992 and 1993. Ethnic Georgians who lived in Abkhazia fought largely on the side of Georgian government forces. Ethnic Armenians ( Bagramyan Battalion ) and Russians within Abkhazia's population largely supported the Abkhazians and many fought on their side. The separatists received support from thousands of North Caucasus and Cossack militants and from the Russian Federation forces stationed in and near Abkhazia.

The handling of this conflict was aggravated by the civil strife in Georgia proper (between the supporters of the ousted Georgian president, Zviad Gamsakhurdia – in office 1991–1992 – and the post-coup government headed by Eduard Shevardnadze) as well as by the Georgian–Ossetian conflict of 1989 onwards.

Significant human rights violations and atrocities were reported on all sides, peaking in the aftermath of the Abkhaz capture of Sukhumi on 27 September 1993, which (according to the Organization for Security and Co-operation in Europe) was followed by a large-scale campaign of ethnic cleansing against the ethnic Georgian population. A fact-finding mission dispatched by the UN Secretary General in October 1993 reported numerous and serious human rights violations committed both by Abkhazians and by Georgians. Approximately 5,000 ethnic Georgians and 4,000 Abkhaz were reported killed or missing, and 250,000 Georgians became internally displaced or refugees.

The war heavily affected post-Soviet Georgia, which suffered considerable financial, human and psychological damage. The fighting and subsequent continued sporadic conflict have devastated Abkhazia. In Abkhazia the conflict is officially named Patriotic War of the People of Abkhazia.

War

The situation in the Autonomous Soviet Socialist Republic of Abkhazia had been tense since the end of the 1980s when the anti-Soviet, Georgian opposition began demanding independence from the Soviet Union. In 1957, 1967, 1978 and 1989, several appeals were issued by Abkhaz intellectuals to the central Soviet authorities in response to Georgian protest movements against the Soviet Union, asking the Soviet government either to establish a separate Abkhaz Soviet Socialist Republic or to move Abkhazia into the Russian Soviet Federative Socialist Republic. The most noteworthy one was the Lykhny Declaration in 1989 signed by the rector of the Sukhumi University. Ethnic Georgian students of the university announced protests. They requested to create a separate branch for Georgian students in Abkhazia. The government approved this by establishing a Tbilisi State University branch in Sukhumi. However, in July 1989, the Georgian students were attacked by ethnic Abkhazians. The Georgian anti-Soviet movement was outraged by the event and included the claims of the students against Abkhazian secession into its list of slogans by several thousand Georgian demonstrators in Tbilisi. In response to the protests Soviet troops were dispatched to Tbilisi, resulting in the April 9 tragedy.

The attack of Abkhazians and the April 9 tragedy eventually resulted in the first armed clashes between the representatives of the Abkhazian and Georgian populations that took place on 16–17 July 1989 in Sukhumi. The resulting civil unrest quickly turned into militarized clashes that, according to official accounts, resulted in 18 deaths and at least 448 wounded, 302 of whom were Georgian. In response, Interior Ministry troops were deployed to quell the unrest.

By July 1990, since neither side had felt strong enough to force the issue militarily, Georgian-Abkhaz antagonisms became largely relegated to the legislatures, demarcating Abkhazia as a legal contest, a "war of laws", until armed hostilities broke out in August 1992. During that time, the government of the Soviet Union had very few options to prevent inter-ethnic conflicts, being itself on the verge of collapse.

In an attempt to reach a peaceful settlement, Georgian President Zviad Gamsakhurdia negotiated on the reform of the electoral law that granted the Abkhaz wide over-representation in the Supreme Soviet, despite Abkhazians being only 18% in Abkhazia, while Georgians were 46%. Ethnic allocations, or quotas, were introduced prior to the 1991 elections to the Supreme Soviet of Abkhazia, resulting in a composition that did not accurately reflect the ethnicity of the constituent population. Thus, of 65 seats, the Abkhazians (17% of the population) gained 28; Georgians (45%), 26; with the remaining 11 being divided amongst other groupings (Armenians, Russians; the latter comprising 33% of the population).

In December 1990, Vladislav Ardzinba was confirmed by Georgian President Zviad Gamsakhurdia as the Chairman of the Supreme Soviet of Abkhazia as a concession. Ardzinba, who was a charismatic but excitable figure popular among the Abkhaz, was believed by Georgians to have helped to instigate the violence of July 1989. However, his election did not stop separatism. Ardzinba, a member of Soyuz faction in the Congress of People's Deputies of the Soviet Union, was directly supported by the pro-Soviet hardliners in Moscow, which encouraged him to take even more bold steps against Georgian leadership in Tbilisi. In 1992, Ardzinba created the Abkhazian National Guard that was mono-ethnically Abkhaz, and initiated a practice of replacing ethnic Georgians in leading positions with Abkhaz. In June 1992, he removed ethnic Georgian Givi Lominadze from the post of the interior minister of Abkhazia, replacing with ethnic Abkhaz Alexander Ankvab. This forced Georgian faction in the Abkhazian Supreme Soviet ("Democratic Abkhazia") to boycott sessions. Interior Minister of Georgia Roman Gventsadze annulled Ardzinba's decision, but Ardzinba refused to obey, despite being obliged to do so by the legislation, and the Abkhazian National Guard stormed the building of the Interior Minister, forcefully removing Lominadze from the office.

The Georgian leadership, being itself dragged in the Civil War, failed to adequatly respond to Russian-supported Abkhaz separatist moves, which were not supported by the majority of population in Abkhazia, especially ethnic Georgians (46% of the population). This eventually led to Abkhazian Supreme Council uniliterally declaring the sovereignity from Georgia on 23 July 1992. This decision was unlawful and it was passed without necessary quorum as the Georgian deputies boycotted the session. No country in the world recognized Abkhazia's sovereignity. On 25 July, State Council of the Republic of Georgia abolished this declaration of sovereignty, but the Abkhazian leadership refused to obey.

Georgian offensive

On 14 August 1992, Georgian police and National Guard units were dispatched to restore the order in Abkhazia. The armed forces were tasked with mission to protect the railroads which were frequently subject to robberies in Abkhazia and Mingrelia because of the weak government control over the regions during the Georgian Civil War. These robberies overally caused damage totaling 9 billion maneti, including to neighboring countries such as Armenia, since Armenia, being a landlocked country, was totally dependent on Georgian ports. The decision to move troops was approved by the State Council of Georgia on 11 August 1992. On 12 August, Georgian troops entered Mingrelia. On 14 August, they peacefully continued their way into Abkhazia; however, near the village of Okhurei, in Ochamchire district, the Abkhazian National Guard opened fire against the Georgian troops. These resulted in clashes which continued while Georgian troops were moving near the villages of Agudzera and Machara. Vladislav Ardzinba stated in his televised address that the "Georgian troops occupied Abkhazia" and "violated its sovereignty", and he proclaimed war against Georgia. State Council of Georgia and its leader Eduard Shevardnadze responded by saying that it is impossible for a country to "occupy" its own territory, every country has a right to move troops on its own territory at its discretion, and that Abkhaz troops were first to open fire.

On 14 August, Georgian troops reached Sokhumi, but despite Abkhazian attacks, they did not enter city. They stopped near a Red Bridge at the outskirts of the city. The negotiations started between Georgian and Abkhazian sides, while Georgians asked to remove Ardzinba for his separatist and war-mongering statements from the post of the chairman of the Supreme Council. The Abkhazian deputies refused. Only after this, on 18 August 1992, the Georgian troops entered Sokhumi and quickly defeated the Abkhaz National Guard. The Abkhazians retreated over the other side of the Gumista River and regrouped their forces in the village of Eshera. This later became the "Western front" of the war. Ardzinba fled to Gudauta, which became a separatist stronghold where they coordinated the military actions. Russian military base of Abkhazia (stationed in Gudauta) supported Abkhaz separatists. The "Eastern front" was formed in Ochamchire district as the Georgians took control over majority-Georgian coastal city Ochamchire (center of the district) and nearby coastal Georgian villages, while Abkhazians took over mountainous miner town Tkvarcheli and nearby Abkhazian-populated villages.

On 15 August, Georgian National Guard and Mkhedrioni made a naval landing  inGagra district and by 19 August, they took control over the whole territory up to the Russian-Georgian border. Separatists in Gugauta were blocked; this severed their auto and railway connections to Russia, the only way they could receive military support from Russia now was through mountains.

On 22 August 1992, the Confederation of Mountain Peoples of the Caucasus published a decree of its president Musa Shanibov and the chairman of the parliament Iysuph Soslanbekov: "As there is no other way to withdraw Georgian occupants' army from the territory of the sovereign Abkhazia and in order to implement the resolution of the 10th Session of the CMPC, we order:

 All headquarters of the Confederation have to dispatch volunteers to the territory of Abkhazia to crush the aggressor militarily.
 All military formations of the Confederation have to conduct military actions against any forces who oppose them and try to reach the territory of Abkhazia by any method.
 To announce Tbilisi as a zone of disaster. At that use all methods, including terrorist acts.
 To declare all people of Georgian ethnicity on the territory of Confederation as hostages.
 All type of cargoes directed to Georgia shall be detained."

On 25 August, Giorgi Karkarashvili, the Georgian military commander, announced via television that the Georgian forces would not take any POWs. He promised that no harm would be done to peaceful residents of Abkhazia and that peace talks would be conducted. He warned separatists that if the peace talks didn't succeed and if 100,000 Georgians were killed, that the remaining 97,000 ethnic Abkhaz, who supported Ardzinba, would perish. Karkarashvili later allegedly threatened the Abkhaz politician Vladislav Ardzinba not to take any actions that would leave the Abkhaz nation without descendants and thus placed the responsibility for future deaths on Ardzinba personally. Later, his speech was used by the separatists as propaganda and to justify their own actions. According to Vicken Cheterian's War and Peace in the Caucasus: "Although the Georgian declarations sound like a threat of genocide, the Georgian leadership was not inclined to organize massacres in Abkhazia and destroy Abkhaz nation... there is no evidence that their objective was mass annihilation of Abkhaz people". Cheterin quotes philosopher Gia Nodia to explain Karkarashvili's statement: "I happened to watch interview of Karkarashvili which was quoted and, although I do not remember the exact wording myself, can say that what he meant was that it is silly on the Abkhaz side to fight, that Georgians will never give up Abkhazia, so the Abkhaz are putting their very existence in danger - even if one hundred thousand people died in the war on each side, Georgians would still be there, but not the Abkhaz. This may have been nasty statement, but Karkarashvili was merely expressing in his own way the idea that was always reiterated by Georgian officials at the time — that it was the radicalism of the Abkhazia's leadership, not Georgia's, that endangered the existence of the Abkhaz as a group". Despite this context, the Abkhazian leadership used this statement for propaganda, falsely claiming that Georgia's aim was to conduct genocide against Abkhazians.

At the end of this stage of the conflict, the Georgian Army had taken most of Abkhazia. Pockets of Abkhaz forces were besieged in parts of Ochamchira District and Tkvarcheli, while in Gudauta they were pinched between Georgian troops in Gagra and Sukhumi.

Ceasefire and Fall of Gagra

On 3 September 1992, a ceasefire was negotiated in Moscow. According to the agreement, Georgian forces were obliged to withdraw from Gagra district. The Georgian side carried out the implementation of the agreement and left its positions. As a result, the local Georgian population of Gagra remained defenseless. The ceasefire was soon violated by the Abkhaz side. Thousands of volunteer paramilitaries, mainly Chechens and Cossacks from the militarized Confederation of Mountain Peoples of the Caucasus (CMPC) and the Abkhaz military, equipped with T-72 tanks, BM-21 Grad rocket launchers, Sukhoi Su-25 attack planes, and helicopters. Georgia accused Russia of supplying this equipment, as it had not been previously used by the Abkhaz. Abkhaz and CMPC forces attacked the town of Gagra on 1 October. The small Georgian force remaining in the town briefly defended Gagra before retreating, then regrouped and recaptured the town. The Abkhaz and CMPC forces reconsolidated and launched another attack, capturing Gagra on 2 October. The Russian navy began to blockade the seaport near Gagra. The naval vessels: "SKP-Bezukoriznenniy", "KIL-25", "BTH-38", "BM-66", "Golovin", "Landing 345", "Aviation 529" ("SU-25", "SU-27"), "MI- and Anti-Aircraft 643". Regiments were commanded by the first deputy Minister of Defense of the Russian Federation, G. Kolesnikov, took part in the occupation of Gagra. The Russian tanker "Don" delivered 420 tons of fuel to Separatist-held Gudauta.

Thousands of Georgian soldiers and civilians fled north, entering Russia before being transported to Georgia proper.

Abkhaz forces, largely supported by the Russian military presence in the region, were now in control over Gagra, Gudauta (where a former Russian military base remains) and Tkvarcheli and rapidly approaching Sukhumi.

The expelled Georgians fled to Russia through the land border or were evacuated by Russian Navy.

Bombing and siege of Sukhumi

In October 1992, two attempts were launched by Abkhaz separatists to take control over Ochamchire city. Both of these attempts failed as Georgians withstood Abkhazian attacks.

On November 29, Abkhaz separatists took control over large Georgian village Kochara near Tkvarcheli, and conducted a campaign of ethnic cleansing against ethnic Georgians.

In December 1992, Abkhaz troops began the shelling of Georgian-held Sukhumi. On 4 March 1993, Eduard Shevardnadze, head of the State Council of Georgia, arrived in the capital of the region to take control over the defensive operations in the city. The Minister of Economy, Beslan Kobakhia, arrived in Sukhumi during the negotiations with Goga Khaindrava. According to Kobakhia, separatist leader Ardzinba would resign if Shevardnadze would do the same. As commander-in-chief of Georgian Military Forces, Eduard Shevardnadze issued the order "measures on the defense of Ochamchira and the Sukhumi regions" that stated: "Military formations of different countries are concentrating in Gudauta and Gumista area. We have information that those forces have the serious goal of seizing Sukhumi and bringing chaos and turmoil to all of Georgia." On 10 February, Shevardnadze appointed Guram Gabiskiria as Mayor of Sukhumi. Meanwhile, the Georgian Parliament made an official declaration blaming Russia for aggression against Georgia and demanding the withdrawal of all Russian military forces from the territory of Abkhazia.

On 16 March 1993, at 6 and 9 am the Abkhaz and the Confederation forces launched a full-scale attack on Sukhumi resulting in mass destruction and heavy casualties among civilians. At 2 am the Abkhaz side began artillery bombardments of Georgian positions at the Gumista River and Sukhumi. Later in the day several Russian Su-25 planes attacked Sukhumi through the morning of the next day. A Russian special detachment led the operation followed by Abkhaz fighters and CMPC volunteers. They crossed the Gumista River and took part of Achadara, but Georgian forces successfully stopped their advance.

On 14 May, a short-lived ceasefire was signed. According to Georgian sources, on 2 July Russian navy ship landed up to 600 Russian Airborne Troops close to the village Tamishi, and engaged in a fierce battle with Georgian troops. The battle was one of the bloodiest in the war, with several hundred killed and wounded on both sides. Despite initial setbacks, the Georgian forces managed to retake their positions. In July, Russian detachments, Abkhaz military and CMPC volunteers captured the villages of Akhalsheni, Guma and Shroma of the Sukhumi region.

Abkhaz offensive on Eshera, Gulripshi, Kamani and Shroma
The villages along the Gumista river (north and east of Sukhumi) such as Achadara, Kamani and Shroma, which were heavily populated by ethnic Georgians became a strategically important area, which enabled motorized units to reach Sukhumi, the capital of Abkhazia. After a failed attempt to storm Sukhumi from the west, the Abkhaz formations and their allies diverted their offensive on the northern and eastern sides of Sukhumi. On 2 July 1993 under Russian military directives and naval support, the Abkhaz and their (Confederation of Mountain Peoples of the Caucasus) allies attacked the villages on the Gumista river. The Georgian side didn't expect any offensive from the northern or eastern side of Sukhumi District. The Georgian forces suffered heavy losses (as many as 500 dead within an hour of the attack) and the defensive line around Sukhumi was breached by the Abkhaz offensive. On 5 July 1993, Abkhaz, Armenian Bagramyan battalion, Russian and North Caucasian detachments stormed the villages of Akhalsheni, Guma and Shroma of Sukhumi district. The last offensive took place on 9 July, on the village of Kamani. Kamani was a Svan (sub-ethnic group of the Georgian people) village, which also included an Orthodox Church (named after St. George) and convent. After the fall of the village, most of its inhabitants (including nuns and priests) were killed by Abkhaz formations and their allies (see Kamani massacre).

By this time, Abkhaz separatists occupied almost all the strategic heights and began to besiege Sukhumi. Soon after, the Chairman of the Georgian Council of Defense of Abkhazia Tamaz Nadareishvili resigned due to ill health and was succeeded by Member of the Georgian Parliament Zhiuli Shartava.

On 15 August 1993, Greece carried out a humanitarian operation, Operation Golden Fleece, evacuating 1,015 Greeks who had decided to flee from the war-ridden Abkhazia.

Similarly, 170 Estonians of Abkhazia were evacuated with three flights by the Republic of Estonia in 1992 (according to another source, around 400 Estonians altogether fled to Estonia during the war).

Fall of Sukhumi

Another Russian-mediated ceasefire was agreed in Sochi on 27 July and lasted until 16 September, when Abkhazian separatists violated the agreement (citing Georgia's failure to comply with the terms of the agreement) and launched a large-scale offensive against Sukhumi. During the siege, Russian jets dropped thermobaric bombs on Georgian residential districts in Sukhumi and Georgian villages along the Gumista River. Russian journalist Dmitry Kholodov stayed in Sukhumi before it fell, and reported that the city was repeatedly shelled by Russian forces, causing heavy civilian casualties.

After a fierce battle, Sukhumi fell on 27 September. Shevardnadze appealed to the population of Sukhumi by radio:

Dear friends, Citizens of Sukhumi and Georgia! Georgia is facing the most difficult days, especially Sukhumi. Separatists and foreign invaders entered into the city. I am proud of your courage... Separatists and opportunists will be judged by history... They do not want Georgians to live in this Georgian city. Many of them dream to repeat the Gagra tragedy here... I know that you understand the challenge we are facing. I know how difficult the situation is. Many people left the city but you remain here for Sukhumi and for Georgia.... I call on you, citizens of Sukhumi, fighters, officers and generals: I understand the difficulties of being in your position now, but we have no right to step back, we all have to hold our ground. We have to fortify the city and save Sukhumi. I would like to tell you that all of us – Government of Abkhazia, Cabinet of Ministers, Mr. Zhiuli Shartava, his colleagues, the city and regional government of Sukhumi, are prepared for action. The enemy is aware of our readiness, that's why he is fighting in the most brutal way to destroy our beloved Sukhumi. I call on you to keep peace, tenacity and self-control. We have to meet the enemy in our streets as they deserve.

Eduard Shevardnadze left the city narrowly escaping death. Almost all members of the Georgian-backed Abkhaz government, who refused to leave the city, including Guram Gabiskiria, Raul Eshba and Zhiuli Shartava, were murdered. Soon Abkhaz forces and the Confederates overran the whole territory of Abkhazia, but the upper Kodori Valley remained in Georgian hands. The total defeat of Georgian forces was accompanied by the ethnic cleansing of the Georgian population.

In the concluding phase of the battle of Sukhumi, the Abkhaz forces shot down three Georgian civilian airliners belonging to Transair Georgia, killing 136 people (some of whom were Georgian soldiers).

Large numbers (about 5,000) of Georgian civilians and servicemen were evacuated by Russian ships during the last hours of the battle.

Russia's role in the conflict
Although Russia officially claimed neutrality during the war in Abkhazia, Russian military officials and politicians were involved in the conflict in several ways. Russia's policy during the war in Abkhazia has been described as inconsistent and "full of ambiguities", shaped by various domestic political actors which argued for different interests. In reaction to the outbreak of conflict, Russian President Boris Yeltsin presented his role as a mediator. In September, 1992, Yeltsin called both sides of the conflict to take part in the negotiations in Moscow. Formally, it was a negotiation between two sovereign states, Georgia and Russia, as Russia accepted internationally established borders of Georgia during that time. However, the negotiations served as a forum for Abkhaz and Georgian sides to discuss the ongoing conflict, while Russia saw its role as a mediator, not a party. On 3 September, 1992, Russian president Boris Yeltsin and Head of State Council of the Republic of Georgia Eduard Shevardnadze signed an agreement, formally known as Summary Document of the Moscow Meeting. This agreement temporarily ended military hostilities in Abkhazia. By this ceasefire, Abkhazia was recognized within the internationally established borders of Georgia.

However, Russian parliament and Russian military took a strong pro-Abkhazian position. Their pressure eventually led to shift in Russia's foreign policy. In parliament, neo-communist/nationalist faction constituted a majority and formed main opposition to Yeltsin's policy. The main motivation was to pressure Georgia to enter CIS and ensure Russia's military presence in the South Caucasus. They also accused Shevardnadze of being responsible for the collapse of the Soviet Union. Russian military had a dominant weight in the formulation of a policy in the Abkhaz Conflict, and it led to Russian Defence Ministry adopting staunch pro-Abkhazian stance. Pavel Grachev, Russian Defence Minister, argued that the loss of Abkhazia would mean the loss of the Black Sea for Russia. The Ministry of Defence took more heavy-handed policy towards Georgia compared to President and the Foreign Ministry.

Russia transferred arms to Georgia under the bilateral agreements on division of Soviet military assets. It included Georgia's main battle tanks, armored personnel carriers, heavy artillery and heavy mortars. The whole Akhaltsikhe motorised rifle division was turned over to Georgia on 22 September 1992. However, on September 25, 1992, Russian Supreme Council (parliament) passed a resolution which condemned Georgia, supported Abkhazia and called for the suspension of the delivery of weapons and equipment to Georgia and the deployment of a Russian peacekeeping force in Abkhazia. It was sponsored by Sergei Baburin, a Russian deputy who met Vladislav Ardzinba and argued that he was not that much sure that Abkhazia was part of Georgia. With the adoption of the resolution, the transfer of military equipment to the Georgian army as part of the ongoing division of Soviet military assets was halted. However, some arms still reached Georgia in semi-legal and illegal ways. Russia's warfare market was the main source of weapons for both conflicting sides.

Some weapons were gained by local raids on Russian Army bases in Akhalkalaki, Batumi, Poti and Vaziani by irregular Georgian paramilitary forces. After several attacks, Russia, including President Boris Yeltsin, condemned Georgia and declared it would defend its bases with force.

Prior to the outbreak of the war, the Abkhaz leadership arranged for the redeployment of a Russian airborne battalion from the Baltic states to Sukhumi. According to the Russian historian Svetlana Mikhailovna Chervonnaya, a number of Russian security servicemen also arrived in Abkhazia as "tourists" during that summer: "The main load in the preparation of Abkhazian events was given to staff of the former KGB. Almost all of them got appointments in Abkhazia under cover of neutral establishments, which had nothing to do with their real activities. To distract attention, various ruses were resorted to, such as the private exchange of apartments, or the necessity of moving one's place of work to Abkhazia due to a sudden deterioration of health."

According to another Russian expert, Evgeni Kozhokin, director of the Russian Institute of Strategic Studies, prior to the outbreak of hostilities, Abkhaz guardsmen had been supplied with weaponry by Russia's 643rd anti-aircraft missile regiment and a military unit stationed in Gudauta. Ardzinba had major supporters in Moscow as well, including Vice President Alexander Rutskoy and the Chechen speaker of the Russian Supreme Soviet, Ruslan Khasbulatov.

After the eruption of armed conflict, the Abkhaz separatist paramilitary units, along with their political supporters fled to Gudauta from where they obtained significant amount of military and financial aid. In Gudauta, the Russian Army base housed and trained Abkhaz paramilitary units and provided protection for the leader of the Abkhaz separatists, Vladislav Ardzinba. The high level of corruption in the Russian military also contributed in the leakage of Russian arms to both sides.

In October 1992, the Abkhaz side violated the previous ceasefire agreement and launched an offensive on Gagra. The Georgian government saw the role of resolution passed by the Russia's parliament in resuming the conflict, and blamed "reactionary forces" in Russia for encouraging the Abkhaz offensive. The action, in which Russian commanders were suspected to have aided to the attackers, also resulted in a significant deterioration of the Georgian-Russian relations. Previously, the Russian military offered protection to the retreating Abkhaz detachments during the summer 1992 Georgian offensive. In November 1992, the Russian Air Force conducted heavy air strikes against the villages and towns in Abkhazia predominantly populated by Georgians. In response, the Georgian Defense Ministry accused Russia for the first time in public of preparing a war against Georgia in Abkhazia. This led to the Georgian attacks on targets under Russian and Abkhaz control and the retaliation from the Russian forces.

Russia's attitude began to tilt further to the Abkhaz side, after a Russian MI-8 helicopter (reportedly carrying humanitarian aid) was brought down by Georgian forces on 27 October, which triggered retaliation from Russian forces. On 14 December 1992, the Russian military suffered the loss of another military helicopter, carrying evacuees from Tkvarcheli, resulting in 52 to 64 deaths (including 25 children). Although Georgian authorities denied any responsibility, many believed the helicopter was shot down by the Georgian forces. On 16 December, the government of Georgia requested the Russians to evacuate their nationals from Abkhazia via other routes, foremost the Black Sea, but also to limit the number of missions flown from Gudauta, the main Russian air base in the area. However, this incident "raised the level of general malevolence in the war and catalyzed more concerted Russian military intervention on the Abkhaz side." The town of Tkvarcheli had been besieged by Georgian forces and its population (mostly Abkhaz, Georgians and Russians) suffered a severe humanitarian crisis. Russian military helicopters supplied the city with food and medicine and mobilized Russian-trained fighters to defend the city.

The Human Rights Watch states: "Although the Russian government continued to declare itself officially neutral in the war, parts of Russian public opinion and a significant group in the parliament, primarily Russian nationalists, who had never been favourably disposed toward the Georgians, began to tilt toward the Abkhaz at least by December." During this period the Abkhaz side obtained a large number of armor, tanks (T-72 and T-80) and heavy artillery. The question remains whether there were specific orders concerning the transfer of weapons to Abkhaz side and if so, whom they were issued by. Russian border guards allowed the Chechen fighters led by Shamil Basayev to cross into Abkhazia or at least did nothing to prevent them from arriving in the conflict zone. The defense minister in the secessionist government and one of the main organizers of the Abkhaz armed units was the professional Russian military officer Sultan Sosnaliyev from the Kabardino-Balkaria Republic.

The most obvious example of Russian support to the Abkhaz side in 1993 was the bombing of Georgian-held Sukhumi by Russian fighter-bombers. The Russian Defence minister Pavel Grachev consistently denied it, but after Georgians succeeded in bringing down one SU-27 fighter-bomber and UN experts identified the dead pilot as Russian, it became irrefutable. Nevertheless, some equipment was turned over to Georgia according to the previous agreements in 1993. Russian general Grachev claimed that the Georgian side had painted the aircraft to resemble a Russian Air Force aircraft and bombed their own positions, supposedly killing hundreds of their own people in Eshera and Sukhumi. This statement was met by the Georgians with outrage.

The Russian journalist Dmitry Kholodov, who has witnessed the Russian bombardment of Sukhumi, wrote a couple of compiling reports with detailed description of humanitarian catastrophe:

"The shelling of Sukhumi by Russians is the most disgusting thing in this war. All the residents of Sukhumi remember the first shelling. It took place on 2 December 1992. The first rocket fell on Peace Street. They struck at crowded places. The next strategic target was the town market, which was hit with great precision. Eighteen people were killed that day. There were always lots of people in the market."

Kholodov also reported on the Russian volunteers fighting on the separatist side:

"Russians, too, are fighting there. We often heard from Georgian guards how Russian mercenaries were attacking: It's a blood-curdling sight – they have helmets and firm, bullet-proof jackets on and their legs are armored as well. They advance with their heads bent down, like robots ready to kill. There is no use shooting at them. No tanks are needed, they are followed by the Abkhaz behind."

On 25 February, the Georgian Parliament appealed to the UN, European Council and Supreme Soviet of the Russian Federation, demanding the withdrawal of Russian forces from Abkhazia and stating that Russia waged "an undeclared war" against Georgia.

Georgian Parliament adopted another resolution on 28 April 1993, which openly blamed Russia in political facilitation of ethnic cleansing and genocide against Georgians.

Russian policy during the final battle for Sukhumi in September 1993, immediately, after the breach of the ceasefire by the Abkhaz forces, appeared to follow several lines. Russian officials condemned the attack, issued calls to Abkhaz forces to cease the offensive and its accompanying human rights violations and reportedly cut off electricity and telephone service to parts of Abkhazia from September to December 1993. Russia also supported resolutions in the Security Council condemning Abkhaz forces for breaching the ceasefire.

At the same time, the Russian government criticized the Georgian government for refusing, once the attack was underway, to negotiate. As the Human Rights Watch report notes, "it is doubtful, however that Russian forces in or near Abkhazia were as surprised as the Russian government seemed to be. Initiating an offensive as large as the one undertaken, in three different directions at once, must have required extensive movement of forces and resupply during the days leading up to it." Russian forces on the Georgian-Abkhaz border, who were supposed to police the ceasefire, made no attempt to forestall the attack. The Abkhaz weapons were stored near the front and were returned to the Abkhaz by the Russians once hostilities restarted. Ataman Nikolay Pusko, a notable commander of some 1,500 Cossack volunteers fighting against Georgians in Abkhazia, later claimed that his sotnia was the first to enter Sukhumi. Pusko and two other Cossack atamans in Abkhazia, Mikhail Vasiliyev and Valery Goloborodko, all died in unclear circumstances from 1993 to 1994.

In a Time magazine article published on 4 October 1993, Georgians said Russian Army officers provided Abkhazian separatists, at the beginning using mere hunting rifles and shotguns, with sophisticated weapons like BM-21 multiple rocket launchers and Sukhoi SU-25 jet aircraft, plus battlefield intelligence.

Humanitarian actions
In the beginning of the conflict (August 1992) Russia evacuated many people from Abkhazian resorts by means of Black Sea fleet and Russian Air Force. As the war progressed Russia began to supply humanitarian aid to both sides, it also brokered numerous agreements concerning the exchange of prisoners of war. In the course of the war, Russian humanitarian efforts were chiefly focused on the town of Tkvarcheli, which had large ethnic Russian population and was besieged by the Georgian forces. The landmines installed along the mountain highway to this town made Russian helicopters the only safe means of transportation into it. However, Russian navy also evacuated tens of thousands of Georgian civilians, after the fall of Gagra (October 1992) and Sukhumi (September 1993) to the separatist forces.

Human rights abuses

Significant ethnic cleansing accompanied by atrocities occurred on both sides with Abkhazians displaced from Georgian-held territory and vice versa. Many human rights abuses, principally looting, pillage and other outlaw acts, along with hostage-taking and other violations of humanitarian law, were committed by all sides throughout Abkhazia. However, the number of Georgian victims exceeded much more the number of Abkhaz victims.

After beginning of the war on 14 August 1992, the Abkhaz separatists and North Caucasian terrorists in Gudauta committed various human rights abuses against ethnic Georgians.

According to Catherine Dale from United Nations High Commissioner for Refugees:

After taking Sukhumi, Georgian forces (including Mkhedrioni paramilitaries) engaged in "vicious, ethnically based pillage, looting, assault and murder." In addition to the looting, Abkhaz cultural monuments were destroyed in a manner that, according to some reports, suggested deliberate targeting. University buildings were sacked and museums and other cultural collections broken up. The irreplaceable Abkhaz national archives were burned by Georgian troops. Reportedly, local firefighters didn't attempt to douse the blaze. A family of Abkhaz refugees from Sukhumi claimed that drunken Georgian troops broke into their apartment firing automatic weapons, and telling them "to leave Sukhumi forever, because Sukhumi is Georgian." According to the family, the Georgian soldiers stole jewelry, assaulted the husband, and then threw them all out into the street. The same witnesses reported seeing dead Abkhaz civilians, including women and elderly people, scattered in the streets, even though the fighting had ended days before.

With the Abkhaz conquest of Gagra, those ethnic Georgians who remained in the district were forcibly expelled, and a total of 429 were killed. One Georgian woman recalled watching her husband being tortured and buried alive:

According to the newspaper "Free Georgia", Chechens and other northern Caucasians rounded up captured soldiers and civilians at the local stadium and executed them. Some were decapitated and their heads were used to play football. After a commission composed of Russian deputies, (as well as a commission of Michael van Praag) went to Gagra and did not confirm the fact of such a brutal attitude towards the Georgians, this newspaper admitted in November that "the episode at the stadium was not confirmed".

After the Abkhaz capture of Sokhumi, one of the largest massacres of the war was committed against the remaining and trapped Georgian civilians in the city.

The 1994 U.S. State Department Country Reports also describes scenes of massive human rights abuse:

The Abkhaz separatist forces committed widespread atrocities against the Georgian civilian population, killing many women, children and elderly, capturing some as hostages and torturing others.... They also killed large numbers of Georgian civilians, who remained behind in Abkhaz-seized territory....

The separatists launched a reign of terror against the majority Georgian population, although other nationalities also suffered. Chechens and other north Caucasians from the Russian Federation reportedly joined local Abkhaz troops in the commission of atrocities.... Those fleeing Abkhazia made highly credible claims of atrocities, including the killing of civilians without regard for age or sex. Corpses recovered from Abkhaz-held territory showed signs of extensive torture (the evidence available to Human Rights Watch supports the U.S. State Department's findings).

Ethnic cleansing of Georgians in Abkhazia

As a result of the war, around 250,000 people (mainly Georgians) fled from or were forced out of Abkhazia. In September 1994, several reports indicated ethnic clashes between Abkhaz and Armenians, a significant part of whom supported the former during the war. Chechen militants of the CMPC later left Abkhazia to take part in the First Chechen War with Russia.

The ethnic cleansing and massacres of Georgians has been officially recognized by the Organization for Security and Co-operation in Europe (OSCE) conventions in 1994, 1996 and again in 1997 during the Budapest, Istanbul and Lisbon summits and condemned the "perpetrators of war crimes committed during the conflict". On 15 May 2008, the UN General Assembly adopted (by 14 votes to 11, with 105 abstentions) a resolution A/RES/62/249 in which it "Emphasizes the importance of preserving the property rights of refugees and internally displaced persons from Abkhazia, Georgia, including victims of reported "ethnic cleansing", and calls upon all Member States to deter persons under their jurisdiction from obtaining property within the territory of Abkhazia, Georgia in violation of the rights of returnees".

The former resident of Ochamchire district, Leila Goletiani, who was taken prisoner by Abkhaz separatists, gave the following account of her captivity to the Russian film director Andrei Nekrasov:

Georgian exodus from Abkhazia

After the fall of Sukhumi in 1993 thousands of Georgian refugees started to flee Gali, Ochamchira and the Sukhumi regions. The plight of refugees became deadly due to snow and cold on the pathway in the Kodori Gorge. Georgian authorities were unable to evacuate all remaining civilians (previously many people were evacuated from Sukhumi by the Russian navy and by the Ukrainian air forces.) The refugees started to move in through the Kodori Gorge on foot, bypassing the Gali region, which was blocked by advancing Abkhaz separatist forces. The crossing of the Kodori Gorge on foot became another death trap for the fleeing IDPs. Most of the people who didn't survive the crossing died of cold and starvation. The survivors who reached the Svan mountains were attacked and robbed by local criminal groups. One of the survivors recalls the crossing:

According to the United States State Department Commission on Foreign Relations and International Relations, 104th Cong., 1st Sess., Country Reports on Human Rights Practices for 1994, at 815 (Joint Comm. Print 1995), the victorious Abkhaz separatists "moved through captured towns with prepared lists and addresses of ethnic Georgians, plundered and burned homes and executed designated civilians." Georgians were specifically targeted, but all non-Abkhaz suffered.

Results
Georgia effectively lost control over Abkhazia and the latter established as a de facto independent territory. The relations between Russia and Abkhazia improved in the late 1990s and the economic blockade of Abkhazia was lifted. The laws were also passed allowing other countries to become part of Russian Federation, which was interpreted by some as an offer to Abkhazia and other unrecognised countries of the former Soviet Union.

Georgia claimed that Russian army and intelligence contributed decisively to the Georgian defeat in the Abkhazian war and considered this conflict (along with the Georgian Civil War and Georgian–Ossetian War) as one of Russia's attempt of restoring its influence in the post-Soviet area.

At the end of the war, the Russian Foreign Minister Andrey Kozyrev said at the UN General Assembly: "Russia realizes that no international organization or group of states can replace our peacekeeping efforts in this specific post-Soviet space."

A wide array of opinions on Russian policy with respect to Georgia and Abkhazia is expressed in the Russian media and parliament. Leonid Radzikhovsky, a political analyst and independent journalist, wrote that gaining new territories is the last thing Russia needs and compared the support of foreign separatists to throwing stones at one's neighbours, while living in the glass house.

Oxford Professor S.N. MacFarlane, notes on the issue of Russian mediation in Abkhazia:
"Notably, it is clear that Russian policy makers are uncomfortable with the idea of a prominent role being granted to external actors in dealing with conflict in the former Soviet space. More recently, this has been extended specifically to the activities of international organisations in the management of conflict. As one group of influential Russian foreign policy commentators and policy makers put it in May 1996, it is definitely not in Russia's interest to see outside mediation and peacekeeping operations on the territory of the former Soviet Union.
"Russia has clear hegemonic aspirations in the former Soviet space. Although a wide array of opinions is expressed on Russian policy in the newly independent states in the media and in parliament, a dominant consensus appears to have emerged among foreign policy influentials on the need for active presence and influence in the area. Such views have been widely expressed in official statements, influential statements by independent policy groups and by advisers to the president, influential political figures and the president himself. The hegemonic component of Russian policy in the near abroad is evident in its efforts to restore Russian control over the external borders of the former Soviet Union, to reassume control over the Soviet air defence network, to obtain agreements on basing Russian forces in the non-Russian republics and by its obvious sensitivity to external military presences (including multilateral ones) on the soil of the former Soviet Union. To judge from Russian policy on Caspian Sea and Central Asian energy development, it extends beyond the political/security realm and into the economic one. Its sources are diverse and include the Russian imperial hangover, but more practically the fate of the Russian diaspora, the lack of developed defences along the borders of the Russian Federation proper, concern over Islam and discomfort with the spill-over effects of instability in the other republics."

On 28 August 2006, Senator Richard Lugar, then visiting Georgia's capital Tbilisi, joined the Georgian politicians in criticism of the Russian peacekeeping mission, stating that "the U.S. administration supports the Georgian government's insistence on the withdrawal of Russian peacekeepers from the conflict zones in Abkhazia and the Tskhinvali district."

Conflict mediation
During the war the peace mediation was done first by Russia and second by the UN. From 1993 onwards, the pressure for a peace settlement mounted from UN, Russia and the then Group of Friends of Georgia (Russia, U.S., France, Germany and UK). In December 1993, an official ceasefire was signed by Georgian and Abkhaz leaders under the aegis of the UN and with Russia as intermediary. The venues shifted from Geneva to New York and finally to Moscow. On 4 April 1994 the "declaration on measures for a political settlement of the Georgian-Abkhazian conflict" was signed in Moscow. Instead of the deployment of a traditional UN peacekeeping force, the deployment of a CIS, mainly Russian peacekeeping forces, was agreed in Moscow on 14 May 1994. In June 1994, CIS peacekeeping forces comprising only the Russian soldiers were deployed along the administrative border between Abkhazia and the remaining Georgia. The UN mission (UNOMIG) also arrived. However, these could not prevent further atrocities against the Georgians in the following years (around 1,500 deaths have been reported by the Georgian government in the post-war period). On 14 September 1994, Abkhaz leaders appeared on local TV to demand that all ethnic Georgians depart from the region by 27 September (the anniversary of the capture of Sukhumi). On 30 November 1994, Abkhazia promulgated a new constitution declaring independence of the breakaway region. However, none of the foreign governments recognised this. On 15 December 1994, the US State Department condemned Abkhazia's declaration of independence. On 21 March 1995, The United Nations High Commissioner for Refugees accused Abkhaz militias of torturing and murdering dozens of returning ethnic Georgian refugees in Gali District.

UN involvement
The United Nations Observer Mission in Georgia (UNOMIG) was established in 1993 to monitor the ceasefire and later expanded to observe the operation of the CIS peacekeeping forces. The Organization for Security in Europe (OSCE) and other international organizations are also involved in monitoring developments. Negotiations toward a permanent peace settlement have made little progress, but the Georgian and Abkhaz governments have agreed to limit the size of their military forces and extend the authorization for UNOMIG. Meanwhile, Georgian refugees maintain a government in exile.

Weapons
Both sides during conflict were mainly equipped with Soviet made weaponry, though Georgian forces had much more heavy weapons at the start of war, Abkhaz forces acquired many advanced weapons from Russia and at the end of war had decisive edge in weaponry, employing many SAM and MANPAT Systems, meanwhile Georgian forces had problems with supplying needed weapons and equipment to forces in Abkhazia, mainly because there was no foreign support and difficulties acquiring weapons from abroad.

See also

Transair Georgia airliner shootdowns
Politics of Abkhazia
Russian-Circassian War
Timeline of the War in Abkhazia (1992–93)
Operation Golden Fleece

Notes

Further reading
 Chervonnaia, Svetlana Mikhailovna. Conflict in the Caucasus: Georgia, Abkhazia and the Russian Shadow. Gothic Image Publications, 1994.
 Blair, Heather. Ethnic Conflict as a Tool of Outside Influence: An Examination of Abkhazia and Kosovo., Young Experts' Think Tank (YETT)
 McCallion, Amy. Abkhazian Separatism, Young Experts' Think Tank (YETT)
 Lynch, Dov, The Conflict in Abkhazia: Dilemmas in Russian 'Peacekeeping' Policy. Royal Institute of International Affairs, February 1998.
MacFarlane, S., N., "On the front lines in the near abroad: the CIS and the OSCE in Georgia' s civil wars", Third World Quarterly, Vol 18, No 3, pp 509– 525, 1997.
Marshania L., Tragedy of Abkhazia Moscow, 1996
White Book of Abkhazia. 1992–1993 Documents, Materials, Evidences. Moscow, 1993.

External links
Accord issue on the Georgia Abkhazia peace process also includes chronology and key texts & agreements.
MAR | Data | Chronology for Abkhazians in Georgia
 World Abaza Congress: Go to death to live.

1992 in Abkhazia
1993 in Abkhazia
1992 in Georgia (country)
1993 in Georgia (country)
Conflicts in 1992
Conflicts in 1993
Ethnic cleansing of Georgians in Abkhazia
Abkhaz–Georgian conflict
Conflicts in territory of the former Soviet Union
Wars involving Chechnya
Wars involving Georgia (country)
Wars involving Russia

War in Abkhazia (1992–1993)


In some programming languages, eval , short for the English evaluate, is a function which evaluates a string as though it were an expression in the language, and returns a result; in others, it executes multiple lines of code as though they had been included instead of the line including the eval. The input to eval is not necessarily a string; it may be structured representation of code, such as an abstract syntax tree (like Lisp forms), or of special type such as code (as in Python). The analog for a statement is exec, which executes a string (or code in other format) as if it were a statement; in some languages, such as Python, both are present, while in other languages only one of either eval or exec is.

Eval and apply are instances of meta-circular evaluators, interpreters of a language that can be invoked within the language itself.

Security risks
Using eval with data from an untrusted source may introduce security vulnerabilities. For instance, assuming that the get_data() function gets data from the Internet, this Python code is insecure:
session['authenticated'] = False
data = get_data()
foo = eval(data)

An attacker could supply the program with the string "session.update(authenticated=True)" as data, which would update the session dictionary to set an authenticated key to be True. To remedy this, all data which will be used with eval must be escaped, or it must be run without access to potentially harmful functions.

Implementation
In interpreted languages, eval is almost always implemented with the same interpreter as normal code. In compiled languages, the same compiler used to compile programs may be embedded in programs using the eval function; separate interpreters are sometimes used, though this results in code duplication.

Programming languages

ECMAScript

JavaScript
In JavaScript, eval is something of a hybrid between an expression evaluator and a statement executor. It returns the result of the last expression evaluated.

Example as an expression evaluator:
foo = 2;
alert(eval('foo + 2'));

Example as a statement executor:
foo = 2;
eval('foo = foo + 2;alert(foo);');

One use of JavaScript's eval is to parse JSON text, perhaps as part of an Ajax framework.  However, modern browsers provide JSON.parse as a more secure alternative for this task.

ActionScript

In ActionScript (Flash's programming language), eval cannot be used to evaluate arbitrary expressions. According to the Flash 8 documentation, its usage is limited to expressions which represent "the name of a variable, property, object, or movie clip to retrieve. This parameter can be either a String or a direct reference to the object instance."

ActionScript 3 does not support eval.

The ActionScript 3 Eval Library and the D.eval API were development projects to create equivalents to eval in ActionScript 3. Both have ended, as Adobe Flash Player has reached its end-of-life.

Lisp
Lisp was the original language to make use of an eval function in 1958.  In fact, definition of the eval function led to the first implementation of the language interpreter.
Before the eval function was defined, Lisp functions were manually compiled to assembly language statements. However, once the eval function had been manually compiled it was then used as part of a simple read-eval-print loop which formed the basis of the first Lisp interpreter.

Later versions of the Lisp eval function have also been implemented as compilers.

The eval function in Lisp expects a form to be evaluated and executed as argument. The return value of the given form will be the return value of the call to eval.

This is an example Lisp code:

; A form which calls the + function with 1,2 and 3 as arguments.
; It returns 6.
(+ 1 2 3)
; In lisp any form is meant to be evaluated, therefore
; the call to + was performed.
; We can prevent Lisp from performing evaluation
; of a form by prefixing it with "'", for example:
(setq form1 '(+ 1 2 3))
; Now form1 contains a form that can be used by eval, for
; example:
(eval form1)
; eval evaluated (+ 1 2 3) and returned 6.

Lisp is well known to be very flexible and so is the eval function. For example, to evaluate the content of a string, the string would first have to be converted into a Lisp form using the read-from-string function and then the resulting form would have to be passed to eval:

(eval (read-from-string "(format t \"Hello World!!!~%\")"))

One major point of confusion is the question, in which context the symbols in the form will be evaluated. In the above example, form1 contains the symbol +. Evaluation of this symbol must yield the function for addition to make the example work as intended. Thus some dialects of lisp allow an additional parameter for eval to specify the context of evaluation (similar to the optional arguments to Python's eval function - see below). An example in the Scheme dialect of Lisp (R5RS and later):

;; Define some simple form as in the above example.
(define form2 '(+ 5 2))
;Value: form2

;; Evaluate the form within the initial context.
;; A context for evaluation is called an "environment" in Scheme slang.
(eval form2 user-initial-environment)
;Value: 7

;; Confuse the initial environment, so that + will be
;; a name for the subtraction function.
(environment-define user-initial-environment '+ -)
;Value: +

;; Evaluate the form again.
;; Notice that the returned value has changed.
(eval form2 user-initial-environment)
;Value: 3

Perl
In Perl, the eval function is something of a hybrid between an expression evaluator and a statement executor. It returns the result of the last expression evaluated (all statements are expressions in Perl programming), and allows the final semicolon to be left off.

Example as an expression evaluator:
$foo = 2;
print eval('$foo + 2'), "\n";

Example as a statement executor:
$foo = 2;
eval('$foo += 2; print "$foo\n";');

Perl also has eval blocks, which serves as its exception handling mechanism (see Exception handling syntax#Perl). This differs from the above use of eval with strings in that code inside eval blocks is interpreted at compile-time instead of run-time, so it is not the meaning of eval used in this article.

PHP
In PHP, eval executes code in a string almost exactly as if it had been put in the file instead of the call to eval(). The only exception is that errors are reported as coming from a call to eval(), and return statements become the result of the function.

Unlike some languages, the argument to eval must be a string of one or more complete statements, not just expressions; however, one can get the "expression" form of eval by putting the expression in a return statement, which causes eval to return the result of that expression.

Unlike some languages, PHP's eval is a "language construct" rather than a function, and so cannot be used in some contexts where functions can be, like higher-order functions.

Example using echo:
<?php
$foo = "Hello, world!\n";
eval('echo "$foo";');
?>

Example returning a value:
<?php
$foo = "Goodbye, world!\n";  //does not work in PHP5
echo eval('return $foo;');
?>

Lua
In Lua 5.1, loadstring compiles Lua code into an anonymous function.

Example as an expression evaluator:
loadstring("print('Hello World!')")()

Example to do the evaluation in two steps:
a = 1
f = loadstring("return a + 1") -- compile the expression to an anonymous function
print(f()) -- execute (and print the result '2')

Lua 5.2 deprecates loadstring in favor of the existing load function, which has been augmented to accept strings. In addition, it allows providing the function's environment directly, as environments are now upvalues.
load("print('Hello ' .. a)", "", "t", { a = "World!", print = print })()

PostScript
PostScript's exec operator takes an operand — if it is a simple literal it pushes it back on the stack. If one takes a string containing a PostScript expression however, one can convert the string to an executable which then can be executed by the interpreter, for example:

 ((Hello World) =) cvx exec
converts the PostScript expression

 (Hello World) =
which pops the string "Hello World" off the stack and displays it on the screen, to have an executable type, then is executed.

PostScript's run operator is similar in functionality but instead the interpreter interprets PostScript expressions in a file, itself.

(file.ps) run

Python
In Python, the eval function in its simplest form evaluates a single expression.

eval example (interactive shell):
>>> x = 1
>>> eval('x + 1')
2
>>> eval('x')
1

The eval function takes two optional arguments, global and locals, which allow the programmer to set up a restricted environment for the evaluation of the expression.

The exec statement (or the exec function in Python 3.x) executes statements:

exec example (interactive shell):
>>> x = 1
>>> y = 1
>>> exec "x += 1; y -= 1"
>>> x
2
>>> y
0

The most general form for evaluating statements/expressions is using code objects. Those can be created by invoking the compile() function and by telling it what kind of input it has to compile: an "exec" statement, an "eval" statement or a "single" statement:

compile example (interactive shell):
>>> x = 1
>>> y = 2
>>> eval (compile ("print 'x + y = ', x + y", "compile-sample.py", "single"))
x + y =  3

D
D is a statically compiled language and therefore does not include an "eval" statement in the traditional sense, but does include the related "mixin" statement.  The difference is that, where "eval" interprets a string as code at runtime, with a "mixin" the string is statically compiled like ordinary code and must be known at compile time.  For example:

import std.stdio;

void main() {
    int num = 0;
    mixin("num++;");
    writeln(num);  // Prints 1.
}

The above example will compile to exactly the same assembly language instructions as if "num++;" had been written directly instead of mixed in. The argument to mixin doesn't need to be a string literal, but arbitrary expressions resulting in a string value, including function calls, that can be evaluated at compile time.

ColdFusion
ColdFusion's evaluate function lets you evaluate a string expression at runtime.
<cfset x = "int(1+1)">
<cfset y = Evaluate(x)>

It is particularly useful when you need to programatically choose the variable you want to read from.
<cfset x = Evaluate("queryname.#columnname#[rownumber]")>

Ruby
The Ruby programming language interpreter offers an eval function similar to Python or Perl, and also allows a scope, or binding, to be specified.

Aside from specifying a function's binding, eval may also be used to evaluate an expression within a specific class definition binding or object instance binding, allowing classes to be extended with new methods specified in strings.

a = 1
eval('a + 1') #  (evaluates to 2)

# evaluating within a context
def get_binding(a)
  binding
end
eval('a+1',get_binding(3)) # (evaluates to 4, because 'a' in the context of get_binding is 3)

class Test; end
Test.class_eval("def hello; return 'hello';end") # add a method 'hello' to this class
Test.new.hello                    # evaluates to "hello"

Forth
Most standard implementations of Forth have two variants of eval: EVALUATE and INTERPRET.

Win32FORTH code example:
  S" 2 2 + ." EVALUATE \ Outputs "4"

BASIC

REALbasic
In REALbasic, there is a class called RBScript which can execute REALbasic code at runtime. RBScript is very sandboxed—only the most core language features are there, and you have to allow it access to things you want it to have. You can optionally assign an object to the context property. This allows for the code in RBScript to call functions and use properties of the context object. However, it is still limited to only understanding the most basic types, so if you have a function that returns a Dictionary or MySpiffyObject, RBScript will be unable to use it. You can also communicate with your RBScript through the Print and Input events.

VBScript
Microsoft's VBScript, which is an interpreted language, has two constructs. Eval is a function evaluator that can include calls to user-defined functions. (These functions may have side-effects such as changing the values of global variables.) Execute executes one or more colon-separated statements, which can change global state.

Both VBScript and JScript eval are available to developers of compiled Windows applications (written in languages which do not support Eval) through an ActiveX control called the Microsoft Script Control, whose Eval method can be called by application code. To support calling of user-defined functions, one must first initialize the control with the AddCode method, which loads a string (or a string resource) containing a library of user-defined functions defined in the language of one's choice, prior to calling Eval.

Visual Basic for Applications
Visual Basic for Applications (VBA), the programming language of Microsoft Office, is a virtual machine language where the runtime environment compiles and runs p-code. Its flavor of Eval supports only expression evaluation, where the expression may include user-defined functions and objects (but not user-defined variable names). Of note, the evaluator is different from VBS, and invocation of certain user-defined functions may work differently in VBA than the identical code in VBScript.

Smalltalk
As Smalltalk's compiler classes are part of the standard class library and usually present at run time, these can be used to evaluate a code string.
Compiler evaluate:'1 + 2'
Because class and method definitions are also implemented by message-sends (to class objects), even code changes are possible:
Compiler evaluate:'Object subclass:#Foo'

Tcl
The Tcl programming language has a command called eval, which executes the source code provided as an argument.  Tcl represents all source code as strings, with curly braces acting as quotation marks, so that the argument to eval can have the same formatting as any other source code.

set foo {
	while {[incr i]<10} {
		puts "$i squared is [expr $i*$i]"
	}
}
eval $foo

bs
bs has an eval function that takes one string argument. The function is both an expression evaluator and a statement executor. In the latter role, it can also be used for error handling. The following examples and text are from the bs man page as appears in the UNIX System V Release 3.2 Programmer's Manual.

Command-line interpreters

Unix shells
The eval command is present in all Unix shells, including the original "sh" (Bourne shell). It concatenates all the arguments with spaces, then re-parses and executes the result as a command.

Windows PowerShell
In Windows PowerShell, the Invoke-Expression Cmdlet serves the same purpose as the eval function in programming languages like JavaScript, PHP and Python.
The Cmdlet runs any Windows PowerShell expression that is provided as a command parameter in the form of a string and outputs the result of the specified expression.
Usually, the output of the Cmdlet is of the same type as the result of executing the expression. However, if the result is an empty array, it outputs $null. In case the result is a single-element array, it outputs that single element. Similar to JavaScript, Windows PowerShell allows the final semicolon to be left off.

Example as an expression evaluator:
PS  > $foo = 2
PS  > invoke-expression '$foo + 2'
Example as a statement executor:
PS  > $foo = 2
PS  > invoke-expression '$foo += 2; $foo'

Microcode
In 1966 IBM Conversational Programming System (CPS) introduced a microprogrammed function EVAL to perform "interpretive evaluation of expressions which are written in a modified Polish-string notation" on an IBM System/360 Model 50. Microcoding this function was "substantially more" than five times faster compared to a program that interpreted an assignment statement.

Theory
In theoretical computer science, a careful distinction is commonly made between eval and apply. Eval is understood to be the step of converting a quoted string into a callable function and its arguments, whereas apply is the actual call of the function with a given set of arguments. The distinction is particularly noticeable in functional languages, and languages based on lambda calculus, such as LISP and Scheme.  Thus, for example, in Scheme, the distinction is between

 (eval '(f x) )

where the form (f x) is to be evaluated, and

 (apply f (list x))

where the function f is to be called with argument x.

Eval and apply are the two interdependent components of the eval-apply cycle, which is the essence of evaluating Lisp, described in SICP.

In category theory, the eval morphism is used to define the closed monoidal category.  Thus, for example, the category of sets, with functions taken as morphisms, and the cartesian product taken as the product, forms a Cartesian closed category.  Here, eval (or, properly speaking, apply) together with its right adjoint, currying, form the  simply typed lambda calculus, which can be interpreted to be the morphisms of Cartesian closed categories.

See also
 Data as code

References

External links
ANSI and GNU Common Lisp Document: eval function
Python Library Reference: eval built-in function
Jonathan Johnson on exposing classes to RBScript
Examples of runtime evaluation in several languages on Rosetta Code

Control flow
Unix SUS2008 utilities
IBM i Qshell commands

Eval


In Etruscan mythology, Ani is god of the sky. He is shown as living in the highest heaven. He is sometimes shown with two faces, possibly showing a link with the Akkadian god Anu and the Roman god Janus.

Notes

References

 Jordan, Michael Encyclopedia of Gods: Over 2,500 Deities of the World New York: Facts on File 1993
 Fischer, Richard James Historical Genesis: from Adam to Abraham University Press of America, 2007

Etruscan gods and goddesses

Ani (god)


David Helwig  (April 5, 1938 – October 16, 2018) was a Canadian editor, essayist, memoirist, novelist, poet, short story writer and translator.

Life and career
Helwig was born in Toronto, Ontario, where he spent his early childhood years. When he was ten years old, his family moved to Niagara-on-the-Lake, Ontario, where his father ran a small business repairing and refinishing furniture and buying and selling antiques. He earned a B.A. from the University of Toronto in 1960, and an M.A. from the University of Liverpool in 1962. He subsequently taught at Queen's University from 1962 to 1974. While he at Queen's University, he also taught writing classes in Collins Bay Penitentiary. In 1972, he co-wrote A Book about Billie with an inmate of the prison.

In 1971, he founded and was long-time editor of the Best Canadian Stories anthology series for Oberon Press. From 1974 to 1976, he was the literary manager for CBC Television's drama department. In 1980, he retired from teaching and became a full-time writer.

His work includes a series of novels set in Kingston, Ontario, known as "The Kingston Novels": The Glass Knight, Jennifer, A Sound Like Laughter, and It is Always Summer. His best known poem, "Considerations", was published in Maclean's in 1970. His poetry collections have received numerous awards, including the CBC poetry award for Catchpenny Poems (1983) and the Atlantic Poetry Award for The Year One (2004). As an adult, Helwig learned Russian and published two books of translations of short stories by Anton Chekhov which included About Love (short story).

He lived his later years in Belfast, Prince Edward Island with his wife, Judy Gaudet. His daughter, Maggie Helwig, is a noted writer and social justice activist in  Toronto.

In 2007, he received the Matt Cohen Award from the Writers' Trust of Canada in honor of his lifetime contribution to Canadian literature. On January 23, 2008, he was appointed Prince Edward Island's third Poet Laureate and on July 1, 2009 he was named a Member of the Order of Canada.

Helwig died on October 16, 2018, at the age of 80 at a hospital in Montague, Prince Edward Island.

Works by David Helwig

Poetry
 Figures in a Landscape, 1968
 The Sign of the Gunman, 1969
 The Best Name of Silence, 1972
 Atlantic Crossings, 1974
 Book of the Hours, 1979
 The Rain Falls Like Rain, 1982
 Catchpenny Poems, 1983
 The Hundred Old Names, 1989
 The Beloved, 1992
 A Random Gospel, 1996
 This Human Day, 2000
 Telling Stories, 2000
 The Year One, 2004
 The Sway of Otherwise, 2008
 Seawrack, 2013
 Keeping Late Hours, 2015
 Sudden and Absolute Stranger, 2017
 A House in Memory: Last Poems, 2020

Fiction
 The Streets of Summer, 1969 (short stories)
 The Day Before Tomorrow, 1971 (titled Message from a Spy in 1975 printing)
 The Glass Knight, 1976
 Jennifer, 1979
 The King's Evil, 1981
 It Is Always Summer, 1982
 A Sound Like Laughter, 1983
 The Only Son, 1984
 The Bishop, 1986
 A Postcard from Rome, 1988
 Old Wars, 1989
 Of Desire, 1990
 Blueberry Cliffs, 1993 (novella)
 Just Say the Words, 1994
 Close to the Fire, 1999 (novella)
 The Time of Her Life, 2000
 The Stand-In, 2002 (novella)
 Duet, 2004 (novella)
 Saltsea, 2006
 Smuggling Donkeys, 2007 (novella)
 Coming Through, 2007 (three novellas)
 Mystery Stories, 2010 (short stories)
 Killing McGee, 2011 (novella)
 Simon Says, 2012
 Clyde, 2014

Other
 A Book About Billie, 1972 (documentary) (as Inside and Out, 1975)
 Last Stories of Anton Chekhov, 1991 (as translator)
 The Child of Someone, 1997 (essays)
 Living Here, 2001 (essays)
 The Names of Things, 2006 (memoir)
 About Love, 2012 (as translator)
 The Essential Tom Marshall, 2012 (co-edited with Michael Ondaatje)

See also

Canadian literature
Canadian poetry
List of Canadian poets

References

Further reading
 Marshall, Tom. Harsh and Lovely Land: The Major Canadian Poets and the Making of a Canadian Tradition. UBC Press, Vancouver, BC, 1979.
 Ruthig, Ingrid, ed. David Helwig: Essays on His Works. Guernica Editions, Toronto, ON, 2018. Introduction, essays, interview, reviews by: George Fetherling, Douglas Glover, D.G. Jones, Simon Lloyd, Tom Marshall, Rob McLennan, Shane Neilson, Ingrid Ruthig, Mark Sampson, and Lorraine M. York.

External links
 David Helwig
David Helwig's  entry in The Canadian Encyclopedia

1938 births
2018 deaths
Canadian male novelists
Canadian male poets
Members of the Order of Canada
20th-century Canadian male writers
20th-century Canadian novelists
20th-century Canadian poets
21st-century Canadian male writers
21st-century Canadian novelists
21st-century Canadian poets
University of Toronto alumni
Writers from Prince Edward Island
Writers from Toronto
Poets Laureate of places in Canada

David Helwig


Nathan Wade Bracken (born 12 September 1977) is a former Australian cricketer. A tall left-arm fast-medium bowler, Bracken is capable of swinging the ball both ways. He has represented Australia in all forms of the game. Bracken represented New South Wales in Australian domestic cricket, Eastern Suburbs in Sydney Grade Cricket and also appeared for English County team Gloucestershire in 2004. On 28 January 2011 he announced his retirement from the game due to a chronic knee injury. On 9 February 2012 it was reported that he sued Cricket Australia over the latter's alleged incompetency in managing his knee injury. With his time representing Australia, Bracken won multiple ICC titles with the team: the 2003 Cricket World Cup, the 2007 Cricket World Cup, and the 2006 ICC Champions Trophy.

Early and personal life

Nathan Bracken was born in Penrith, New South Wales to parents Gordon and Robin. He spent his childhood living in the Blue Mountains region of New South Wales, attending Faulconbridge Primary and Springwood High School. He currently resides on the Central Coast of New South Wales and is married to Haley Bracken with whom he has 2 children named Chase and Tag. He is also studying for an undergraduate degree in communications. Bracken contested the Australian House of Representatives seat of Dobell as an independent against sitting member Craig Thomson at the 2013 federal election and received an 8.2 percent primary vote.

Domestic career

First-class cricket

After a stint at the Australian Cricket Academy in 1997, Bracken made his first-class debut for New South Wales against Queensland on 27 October 1998 at Manuka Oval, Canberra. New South Wales were beaten by an innings and Bracken finished with figures of 0/86 off 41 overs. He played 5 more first-class matches in the 1998–99 season and finished with 11 wickets at a respectable average of 30.36. The 1999–00 season saw Bracken only play one match, however the 2000–01 season was one of great success for Bracken. He finished the season as New South Wales second leading wicket-taker behind Stuart MacGill with 29 wickets at 23.72. As a result of his outstanding season he was rewarded with a place in the Australian squad for the 2001 Ashes tour, a Cricket Australia contract and won the 2001 Bradman Young Cricketer of the Year award.

After recovering from a shoulder injury he sustained on the 2001 Ashes tour, Bracken played 8 matches for New South Wales in the 2001–02 season. He had a successful season once again, claiming 24 wickets at 31.79 and finishing behind Stuart Clark as the second leading wicket taker for New South Wales. 2002–03 was a season that saw Bracken struggle as he only took 16 wickets in 6 matches at a rather expensive 36.62. 2003–04 saw Bracken make his Test debut and as a result, he appeared less frequently for New South Wales. Despite this, he still performed well in the 4 matches he participated in, taking 16 wickets at 24.75. Following this season, Bracken was signed by Gloucestershire to play in the English first-class competition as a replacement for Mike Smith. Bracken only played 2 matches for the club, however he was quite successful and took 5 wickets at 21.20 with best figures of 2/12 coming against Lancashire.

2004–05 was Bracken's best season for New South Wales to date. He played in all 11 matches and took 43 wickets at an average of 18.79. The season contained a number of memorable performances by Bracken including a phenomenal spell of 7/4 off 7 overs to help dismiss South Australia for a mere 29 runs at the Sydney Cricket Ground on 2 December 2004. The figures were Bracken's best ever at the time, and are amongst the most impressive figures seen in Australian domestic cricket history. He also played an enormous part in New South Wales' thrilling 1 wicket win in the final against Queensland, winning Man of the Match. Bracken claimed 6/27 in 13.2 overs to help bowl out Queensland for 102 in their first innings and took an important 2/54 in their second innings. To add to this, Bracken scored an invaluable 11* to guide his team home to their target of 183 after New South Wales were 9/161, still needing 22 for victory. 2005–06 saw a return to the Test team for Bracken and as a result, fewer matches for New South Wales. Bracken still performed strongly in his few games, taking 13 wickets at 17.53. After only playing 2 matches in the 2006–07 season, the Blues enjoyed Bracken's services in their Pura Cup winning 2007–08 season as he appeared in the final and took 22 wickets at 21.22 during the season.

List A cricket
Bracken made his List A debut for New South Wales against the now defunct Canberra Comets on 31 October 1998 at Manuka Oval, Canberra. New South Wales won the match and Bracken was rather economical taking 0/19 off his 5 overs. After a Man of the Match performance against Queensland in the semi-final of the Mercantile Mutual Cup, Bracken was selected in the New South Wales team to meet Victoria in the final in only his 5th List A game. Bracken was economical, taking 0/28 off his 10 overs however New South Wales still lost the final by 39 runs.

After only playing one match in the 1999–00 season, the 2000–01 season proved to be a successful one for Bracken as he made his One Day International debut and helped New South Wales to win the Mercantile Mutual Cup. Bracken took 11 wickets at an average of 25.00, including figures of 2/43 in the final against Western Australia. He continued his good form into the 2001–02 season, helping New South Wales claim their second consecutive One Day title, this time over Queensland. Bracken took 18 wickets at 21.88 during the season, which included his best List A performance to date, as he took 5/38 against Victoria at the Melbourne Cricket Ground. 2002–03 was another successful season for both Bracken and New South Wales, as the Blues recorded their third consecutive domestic One Day title and Bracken claimed 15 scalps at 23.66. Bracken was once again a leading performer in the final, taking 2/35 off his 10 overs as New South Wales cruised to a 7 wicket win.

After three seasons of success, Bracken struggled for New South Wales in both the 2003–04 and 2004–05 seasons taking 3 wickets at 76.33 and 7 wickets at 44.71 respectively. International commitments left Bracken out of the side for a large majority of the 2005–06 One Day season, however he performed well in his limited appearances, claiming 5 wickets at 21.60. Once again, Bracken's international duties kept him out of a large majority of the 2006–07 and 2007–08 seasons and he took 3 wickets at 54.33 and 5 wickets at 37.80 respectively.

International career

Test cricket

Bracken made his Test debut for Australia on 4 December 2003 against India in the Border-Gavaskar Trophy as a replacement for the injured Glenn McGrath. In a drawn Test, Bracken had a respectable debut Test claiming 1/90 off 26 overs in the first innings and 2/12 off 4 overs in the second. Despite this, Bracken was dropped for Western Australian paceman Brad Williams for the Second Test at Adelaide. The selectors chose Bracken ahead of Andrew Bichel for the final two Tests and in a drawn series that saw most bowlers struggle, he finished with 6 wickets at 58.50.

Due to the strength of fast bowling in Australia, Bracken was kept out of the Test team for nearly 2 years until he was selected in the Australian side for the 1st Test of the 2005–06 Frank Worrell Trophy against the West Indies in Brisbane. It was in this match that Bracken recorded both his best Test batting and bowling performances to date. In Australia's first innings he struck 37 off 51 balls and in the West Indians' second innings, Bracken claimed figures of 4/48 off 16 overs including the wickets of Brian Lara and Shivnarine Chanderpaul. Despite this good all-round performance, leg spinner Stuart MacGill was favoured by the selectors for the remaining Tests in the series. In December 2005, Bracken played the 1st Test against South Africa at the WACA Ground before once again being dropped in favour of Stuart MacGill.

Bracken has not played another Test since then due to the rise of Stuart Clark and Mitchell Johnson however in February 2008 he claimed that he was still eager to claim a spot in the Test team. Bracken is considered unlucky by many for his lack of Test starts given his one-day form – leading to comparisons with Michael Bevan.

One Day cricket
Bracken made his debut for Australia on 11 January 2001 against the West Indies. Although putting in respectable performances with the ball, he could not manage an assured place in the side due to both injuries and the strength of the Australian team. However, after Jason Gillespie was dropped from the national side, Bracken returned for the 2005 ICC Super Series against the World XI. This began the start of a sustained run in the national team and rise of Bracken as an international cricketer.

In the record-breaking fifth ODI during Australia's Tour of South Africa in 2006, Bracken achieved his maiden 5 wicket haul, taking 5-67 off 10 overs. He was the only bowler in the match to concede less than 7 runs an over. From the third ODI of that tour until the 5th match of the Commonwealth Bank series in 2007, Bracken went on a 17 match streak of taking at least a wicket a game. His consistency was rewarded with a place in the 2007 World Cup winning team and took 16 wickets during the campaign.

On 8 February 2008, Bracken achieved his best ever international figures taking 5–47 against Sri Lanka in Sydney. On 8 July Bracken displaced Daniel Vettori as the no. 1 ranked ODI bowler in the world following the series against the West Indies. He was also named in the ICC World ODI team of the year in 2008 and awarded Australia's ODI player of the year at the 2009 Allan Border Medal ceremony. Bracken played his last ODI on 17 September 2009 after succumbing to a knee injury and being ruled out of the 2009 ICC Champions Trophy. This would be his last appearance in Australian colours as the selectors moved on towards younger players. Bracken later announced he would quit from all forms of international cricket on 29 January 2011.

He finished with 174 ODI wickets at an average of 24.36 and proved to be a vital member of the Australian One Day International side during his career. With a combination of accuracy, swing and cutters, Bracken established himself as one of the most effective limited overs bowlers in the world.

Career highlights

Tests
Test Debut: vs India at the Brisbane Cricket Ground, 4 December 2003 (cap 387).

 Bracken's 1st Test wicket was that of Virender Sehwag, caught by Matthew Hayden (1st match).
 Bracken's best bowling figures of 4/48 off 16 overs came against the West Indies at the Brisbane Cricket Ground, 6 November 2005
 Bracken's highest score of 37 came against the West Indies at the Brisbane Cricket Ground, 4 November 2005

One Day Internationals
One Day International Debut: vs West Indies at the Melbourne Cricket Ground, 11 January 2001 (cap 142).

 Bracken's 1st One Day International wicket was that of Sherwin Campbell, caught by Michael Bevan (1st match).
 Bracken's 50th One Day International wicket was that of Sanath Jayasuriya, caught by Andrew Symonds (31st match).
 Bracken's 100th One Day International wicket was that of Makhaya Ntini, bowled (60th match).
 Bracken's best bowling figures of 5/47 off 8.3 overs came against Sri Lanka at the Sydney Cricket Ground, 8 February 2008
 Bracken's highest score of 21* off 12 balls came against New Zealand at Jade Stadium, 10 December 2005
 Took figures of 3/22 against the West Indies in the final of the 2006 ICC Champions Trophy
 He was part of Australia's Cricket World Cup winning squads in both 2003 and 2007.

Twenty20 Internationals
Twenty20 International Debut: vs South Africa at the Brisbane Cricket Ground, 9 January 2006 (cap 14).

 Bracken's 1st Twenty20 International wicket was that of Boeta Dippenaar, caught by Brad Haddin (1st match).
 Bracken's best bowling figures of 3/11 off 2.3 overs came against India at the Melbourne Cricket Ground, 1 February 2008
 Bracken's highest score of 4 off 3 balls came against Zimbabwe at Newlands Cricket Ground, 12 September 2007

Awards
 Bradman Young Cricketer of the Year – 2001.
 Bracken has won three One Day International and one Twenty20 International Man of the Match awards.
 Man of the Series in the 2007–08 Commonwealth Bank Series.

Achievements and records
 Bracken finished as Australia's leading wicket taker in One Day International cricket for the year 2006 with 46 wickets at an average of 18.82.
 Bracken reached 100 One Day International wickets in his 60th match. This made him the second fastest Australian to reach the milestone, equal with Shane Warne and Dennis Lillee.
 Pura Cup final winner: 2004–05, 2007–08
 Australian One Day Domestic Cup final winner: 2000–01, 2001–02, 2002–03
 ICC Champions Trophy final winner: 2006
 ICC Cricket World Cup final winner: 2007

Post-career
After his retirement from cricket, Bracken stood as the Liberal Party's candidate for The Entrance in the 2023 New South Wales state election. He was not elected.

References

External links

1977 births
Australia One Day International cricketers
Australia Test cricketers
Australia Twenty20 International cricketers
Australian cricketers
Australian Institute of Sport cricketers
Cricketers at the 2003 Cricket World Cup
Cricketers at the 2007 Cricket World Cup
Cricketers from Sydney
Gloucestershire cricketers
Independent politicians in Australia
Living people
New South Wales cricketers
People from the Blue Mountains (New South Wales)
People from the Central Coast (New South Wales)
Royal Challengers Bangalore cricketers
Sportsmen from New South Wales

Nathan Bracken


Alexander Suss Langsdorf Jr. (May 30, 1912 – May 24, 1996) was an American physicist on the team that developed the atomic bomb and several devices related to nuclear physics. He was a vocal opponent of the use and proliferation of nuclear weapons.

Life and career
Langsdorf was born in St. Louis, Missouri. He earned an undergraduate degree from Washington University in St. Louis in 1932 and a doctorate in physics from Massachusetts Institute of Technology in 1937. In this time he developed a continuously sensitive cloud chamber. After a research fellowship at the University of California at Berkeley, he became a physics instructor at Washington University in St. Louis from 1939 to 1942.

Prior to World War II, Langsdorf co-developed a cyclotron for splitting atomic particles at Washington University in St. Louis . It was designed for use in medical research. During World War II, he worked with Enrico Fermi at the University of Chicago on the Manhattan Project. Langsdorf was one of the designers of the first two nuclear reactors after Fermi completed the first sustained nuclear chain reaction in 1942. Langsdorf was able to produce a tiny usable sample of plutonium using his device. That sample was then used in the Trinity nuclear test on July 16, 1945. Langsdorf urged President Harry S Truman not to use the bomb against the Japanese, but a plutonium-based bomb was dropped on Nagasaki soon after.

He continued to urge against expansion of nuclear weapons. He helped found Bulletin of the Atomic Scientists, and his wife Martyl Langsdorf designed the 1947 cover of the publication which debuted the Doomsday Clock. Langsdorf also invented the diffusion cloud chamber and the reactor oscillator.

Langsdorf died in Elmhurst, Illinois, from complications from hip surgery.

References

External links
1965 Audio Interview with Alexander Langsdorf Jr. by Stephane Groueff Voices of the Manhattan Project
Alexander Langsdorf Jr. Papers via Washington University in St. Louis

1912 births
1996 deaths
Scientists from St. Louis
Washington University physicists
Physicists from Missouri
Manhattan Project people
Fellows of the American Physical Society
Washington University in St. Louis alumni
Massachusetts Institute of Technology alumni
University of California, Berkeley fellows
Washington University in St. Louis faculty

Alexander Langsdorf Jr.


The Next-Generation Transit Survey (NGTS) is a ground-based robotic search for exoplanets. The facility is located at Paranal Observatory in the Atacama desert in northern Chile, about 2 km from ESO's Very Large Telescope and 0.5 km from the VISTA Survey Telescope. Science operations began in early 2015. The astronomical survey is managed by a consortium of seven European universities and other academic institutions from Chile, Germany, Switzerland, and the United Kingdom. Prototypes of the array were tested in 2009 and 2010 on La Palma, and from 2012 to 2014 at Geneva Observatory.

The aim of NGTS is to discover super-Earths and exo-Neptunes transiting relatively bright and nearby stars with an apparent magnitude of up to 13. The survey uses transit photometry, which precisely measures the dimming of a star to detect the presence of a planet when it crosses in front of it. NGTS consists of an array of twelve commercial 0.2-metre telescopes (f/2.8), each equipped with a red-sensitive CCD camera operating in the visible and near-infrared at 600–900 nm. The array covers an instantaneous field of view of 96 square degrees (8 deg2 per telescope) or around 0.23% of the entire sky. NGTS builds heavily on experience with SuperWASP, using more sensitive detectors, refined software, and larger optics, though having a much smaller field of view. Compared to the Kepler spacecraft with its original Kepler field of 115 square degrees, the sky area covered by NGTS will be sixteen times larger, because the survey intends to scan four different fields every year over a period of four years. As a result, the sky coverage will be comparable to that of Kepler's K2 phase.

NGTS is suited to ground-based photometric follow-up of exoplanet candidates from space-based telescopes such as TESS, Gaia and PLATO. In turn, larger instruments such as HARPS, ESPRESSO and VLT-SPHERE may follow-up on NGTS discoveries with a detailed characterization to measure the mass of a large number of targets using Doppler spectroscopy (wobble method) and make it possible to determine the exoplanet's density, and hence whether it is gaseous or rocky. This detailed characterization allows to fill the gap between Earth-sized planets and gas giants as other ground-based surveys can only detect Jupiter-sized exoplanets, and Keplers Earth-sized planets are often too far away or orbit stars too dim to allow for the planet's mass determination. NGTS's wider field of view also enables it to detect a larger number of more-massive planets around brighter stars.

Science mission

Ground-based surveys for extrasolar planets such as WASP and the HATNet Project have discovered many large exoplanets, mainly Saturn- and Jupiter-sized gas giants. Space-based missions such as CoRoT and the Kepler survey have extended the results to smaller objects, including rocky super-Earth- and Neptune-sized exoplanets. Orbiting space missions have a higher accuracy of stellar brightness measurement than is possible via ground-based measurements, but they have probed a relatively small region of sky. Unfortunately, most of the smaller candidates orbit stars that are too faint for confirmation by radial-velocity measurements. The masses of these smaller candidate planets are hence either unknown or poorly constrained, such that their bulk composition cannot be estimated.

By focusing on super-Earth- to Neptune-sized targets orbiting cool, small, but bright stars of K and early-M spectral type, over an area considerably larger than that covered by space missions, NGTS is intended to provide prime targets for further scrutiny by telescopes such as the Very Large Telescope (VLT), European Extremely Large Telescope (E-ELT), and the James Webb Space Telescope (JWST). Such targets are more readily characterized in terms of their atmospheric composition, planetary structure, and evolution than smaller targets orbiting larger stars.

In follow-up observations by larger telescopes, powerful means will be available to probe the atmospheric composition of exoplanets discovered by NGTS. For example, during secondary eclipse, when the star occults the planet, a comparison between the in-transit and out-of-transit flux allows computation of a difference spectrum representing the thermal emission of the planet. Calculation of the transmission spectrum of the planet's atmosphere can be obtained by measuring the small spectral changes in the spectrum of the star that arise during the planet's transit. This technique requires an extremely high signal-to-noise ratio, and has thus far been successfully applied to only a few planets orbiting small, nearby, relatively bright stars, such as HD 189733 b and GJ 1214 b. NGTS is intended to greatly increase the number of planets that area analyzable using such techniques. Simulations of expected NGTS performance reveal the potential of discovering approximately 231 Neptune- and 39 super-Earth-sized planets amenable to detailed spectrographic analysis by the VLT, compared to only 21 Neptune- and 1 super-Earth-sized planets from the Kepler data.

Instrument

Development

The scientific goals of the NGTS require being able to detect transits with a precision of 1 mmag at 13th magnitude. Although at ground level this level of accuracy was routinely achievable in narrow-field observations of individual objects, it was unprecedented for a wide-field survey. To achieve this goal, the designers of the NGTS instruments drew upon an extensive hardware and software heritage from the WASP project, in addition to developing many refinements in prototype systems operating on La Palma during 2009 and 2010, and at the Geneva Observatory from 2012 to 2014.

Telescope array

NGTS employs an automated array of twelve 20-centimeter f/2.8 telescopes on independent equatorial mounts and operating at orange to near-infrared wavelengths (600–900 nm). It is located at the European Southern Observatory's Paranal Observatory in Chile, a location noted for low water-vapor and excellent photometric conditions.

Combined search

The NGTS telescope project cooperates closely with ESO's large telescopes. ESO facilities available for follow-up studies include the High Accuracy Radial Velocity Planet Searcher (HARPS) at La Silla Observatory; ESPRESSO for radial-velocity measurements at the VLT; SPHERE, an adaptive optics system and coronagraphic facility at the VLT that directly images extrasolar planets; and a variety of other VLT and planned E-ELT instruments for atmospheric characterization.

Partnership

Although located at Paranal Observatory, NGTS is not in fact operated by ESO, but by a consortium of seven academic institutions from Chile, Germany, Switzerland, and the United Kingdom:
 DLR, Institute for Planetary Research
 Geneva Observatory
 Queen's University Belfast
 University of Cambridge
 University of Chile
 University of Leicester
 University of Warwick

Results
 On 31 October 2017, the discovery of NGTS-1b, a confirmed hot Jupiter-sized extrasolar planet orbiting NGTS-1, an M-dwarf star, about half the mass and radius of the Sun, every 2.65 days, was reported by the survey team. Daniel Bayliss, of the University of Warwick, and lead author of the study describing the discovery of NGTS-1b, stated, "The discovery of NGTS-1b was a complete surprise to us—such massive planets were not thought to exist around such small stars – importantly, our challenge now is to find out how common these types of planets are in the Galaxy, and with the new Next-Generation Transit Survey facility we are well-placed to do just that."
 On 3 September 2018, the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34 day orbit. NGTS-4b has a mass 20.6 ± 3.0  and radius 3.18 ± 0.26 , which places it well within the so-called "Neptunian desert". The mean density of the planet (3.45 ± 0.95 g cm−3) is consistent with a composition of 100% H2O or a rocky core with a volatile envelope.

Discoveries

Planets
This is a list of planets discovered by this survey. This list is incomplete, and requires more information.

Brown dwarfs

In addition, the survey has discovered two brown dwarfs.

See also
 List of extrasolar planets

Other exoplanet search projects

 HATNet Project (HAT)
 Miniature Exoplanet Radial Velocity Array (MINERVA)
 Kilodegree Extremely Little Telescope (KELT)
 Trans-Atlantic Exoplanet Survey (TrES)
 Wide Angle Search for Planets (WASP and SuperWASP)
 XO Telescope
 Microlensing Observations in Astrophysics (MOA)
 Optical Gravitational Lensing Experiment (OGLE)
 Anglo-Australian Planet Search (AAPS)
 Cool Companions on Ultrawide Orbits (COCONUTS)
 Transiting Planets and Planetesimals Small Telescope (TRAPPIST)
 Search for Habitable Planets Eclipsing Ultra-cool Stars (SPECULOOS)

Notes

References

External links

 The Next Generation Transit Survey Becomes Operational at Paranal, ESO archive, The Messenger 165 – September 2016

Articles containing video clips
Astronomical instruments
Astronomical surveys
European Southern Observatory
Exoplanet search projects by small telescope
Telescopes

Next-Generation Transit Survey