Relations between Iran and the United States have been mostly confrontational since 1979, when Iran's Islamic Revolution removed from power the U.S.-backed government of the Shah and replaced it with a Shia-cleric dominated system. Successive U.S. administrations have treated Iranian policies as a threat to U.S. interests in the Middle East, particularly Iran's support for terrorist and other armed groups and, after 2002, its nuclear program. Following its 2018 withdrawal from the 2015 multilateral nuclear agreement with Iran (Joint Comprehensive Plan of Action, JCPOA), the Trump Administration has taken several steps in its campaign of applying "maximum pressure" on Iran. These steps include designating the Islamic Revolutionary Guards Corps-Qods Force (IRGC-QF) as a Foreign Terrorist Organization (FTO), ending a U.S. sanctions exception for the purchase of Iranian oil to bring Iran's oil exports to "zero," and deploying additional U.S. military assets to the region. Tensions have increased significantly since May 2019, as Iran (and Iran-linked forces) have apparently responded by attacking and seizing commercial ships, posing threats to U.S. forces and interests (including downing a U.S. unmanned aerial vehicle), causing destruction to some critical infrastructure in the Arab states of the Persian Gulf, and reducing compliance with the provisions of the JCPOA. On December 27, 2019, a rocket attack on a base near Kirkuk in northern Iraq killed a U.S. contractor and wounded four U.S. servicemembers and two Iraqi servicemembers. Two days later, the United States launched retaliatory airstrikes on five facilities (three in Iraq, two in Syria) used by the Iran-backed Iraqi armed group Kata'ib Hezbollah (KH), a U.S.-designated FTO to which the United States attributed the December 27 and other attacks. On December 31, 2019, supporters of Kata'ib Hezbollah and other Iran-backed Iraqi militias surrounded the U.S. Embassy in Baghdad, forcing their way into the compound and setting some outer buildings on fire. No U.S. personnel were reported harmed at the Embassy, but Secretary of Defense Mark Esper announced the deployment of an additional infantry battalion "in response to increased threat levels against U.S. personnel and facilities, such as we witnessed in Baghdad." President Trump tweeted that Iran, which "orchestrat[ed the] attack," would "be held fully responsible for lives lost, or damage incurred, at any of our facilities. They will pay a very BIG PRICE!" On January 2, 2020, the U.S. Department of Defense announced in a statement that the U.S. military had killed IRGC-QF Commander Major General Qasem Soleimani in a "defensive action." The statement cited Soleimani's responsibility for "the deaths of hundreds of Americans and coalition servicemembers" and his approval of the embassy blockade in Baghdad, and asserted that he was "actively developing plans to attack American diplomats and servicemembers in Iraq and throughout the region." According to subsequent media reports and Administration statements, Soleimani was killed in a U.S. drone strike while leaving Baghdad International Airport early on the morning of January 3 local time; KH founder and Iraqi Popular Mobilization Forces (PMF) leader Abu Mahdi Al Muhandis and other Iranian and Iraqi figures also were killed in the strike. Soleimani was widely regarded as one of the most powerful and influential figures in Iran, perhaps second only to Supreme Leader Ali Khamene'i, to whom Soleimani reportedly had a direct channel. As head of the IRGC-QF, Soleimani was the driving force behind Iran's external military operations, including the campaign to keep the Asad government in power in Syria. Some analysts argue that his death is likely to have a dramatic impact on Iran's capabilities, with one expert describing him as "the military center of gravity of Iran's regional hegemonic efforts" and "an operational and organization genius who likely has no peer in the upper ranks of the Islamic Revolutionary Guard Corps." Others contend that while Soleimani was undoubtedly important, "he was only the agent of a government policy that preceded him and will continue without him." U.S. officials have explained the timing and rationale behind the strike in a number of ways. Administration officials claim that Soleimani posed a direct threat and that he was involved in planning an "imminent" attack that would put U.S. lives at risk. Some Members of Congress have challenged that assertion, publicly contesting the evidence presented by the Administration in a classified setting. President Trump said in a January 10 interview that he believed Soleimani was involved in planning "large-scale attacks" on "four embassies," while Secretary Esper said on January 12 that he "didn't see" specific intelligence indicating such a threat. Some Members of Congress have also challenged this rationale in light of reports that another IRGC-QF commander was targeted in Yemen on the same day as the Soleimani strike (see below). The Administration has also argued that striking Soleimani was an attempt to deter future Iranian aggression. Striking Soleimani would appear to be of greater magnitude than previous U.S. responses, such as additional troop deployments, that were carried out with the stated intention of deterring Iran. Those responses arguably did not do so (given the December 27 rocket strike and other Iranian actions). This killing thus may be an attempt to alter Iran's decision-making calculus. Some have suggested that the December 27 death of the American contractor in Iraq and the subsequent embassy blockade compelled President Trump to order the strike. Secretary of State Mike Pompeo has underscored that the United States is not seeking further escalation. Iran's leaders, including Supreme Leader Khamene'i and President Hassan Rouhani, have vowed revenge for Soleimani's killing. Khamene'i declared three days of public mourning, and large crowds, estimated in the hundreds of thousands in some cases, attended funeral processions for Soleimani across Iran. One analyst argues that, because of Soleimani's personal popularity across the Iranian political spectrum, his death "will create a rally to the flag," likely strengthening hardliners in advance of legislative elections scheduled for February 2020. Others caution that the crowds, brought about in part by government coercion, are also "images that are destined for domestic consumption but more so for foreign consumption to display popular support for the regime." Early on January 8, 2020 (Iraq local time), in its first action since Soleimani's death, Iran launched several ballistic missiles targeting at least two Iraqi military bases where U.S. forces are located. The U.S. Department of Defense said the missiles, of which there were more than a dozen, were launched from Iran. Both the U.S. and Iraqi militaries reported no casualties. President Trump appeared to downplay the attack, tweeting that "All is well!" and "So far, so good!" Iranian officials conveyed different messages about the strike and whether it represented the entirety of Iran's response. Iranian Foreign Minister Javad Zarif tweeted that Iran "took & concluded proportionate measures," while Supreme Leader Khamene'i tweeted that "such military actions are not enough." Debate remains about whether Iran intended to inflict casualties in the attack: an Iranian general said that Iran "did not intend to kill," while Chairman of the Joints Chief of Staff Army General Mark Milley and Secretary Pompeo have said that Iran did have that intention. Some outside analysts contend that Iran was seeking to demonstrate its ability to kill Americans while stopping short of doing so. Further Iranian response could take several forms. Possible Iranian retaliatory measures could include mobilizing militias it supports to attack U.S. forces deployed in Iraq, Syria, and/or Afghanistan; conducting strikes on oil production facilities or tankers, U.S. military installations, or other targets in the Gulf; activating proxies and operatives to execute "more asymmetric or unconventional-style hits" through Europe, South America, or elsewhere; cyber attacks; or other responses. The confrontation also could heighten the prospect of additional Iranian steps in breach of the JCPOA (see below), perhaps dealing a "fatal blow" to the accord and international attempts to preserve it. Regarding the threat posed by possible Iranian retaliation, Secretary Pompeo said on January 5 that "there is a real likelihood that Iran will make a mistake and make a decision to go after some of our forces," while also maintaining that, "There is less risk today to American forces in the region as a result of" Soleimani's death. Iranian options may be constrained by increased domestic upheaval in the wake of its January 8, 2020, downing of a civilian airliner. Several hours after Iranian forces launched missiles at Iraqi bases, a Ukraine International Airlines passenger flight crashed shortly after taking off from Tehran, killing all 176 on board. The Iranian government stated that the crash was caused by a mechanical failure and pledged to investigate the incident, which it described as unrelated to the missile launch. However, international pressure grew in light of evidence that the plane had been shot down by the Iranian military, and after Canada (which had 57 citizens killed in the crash) and several other countries publicly charged Iran with downing the plane, the Iranian government admitted that the plane had been shot down by a Russian-made Tor-M1 (or SA-15) surface-to-air missile, attributing the firing to "human error." Demonstrators subsequently gathered in Tehran and elsewhere to demand accountability and condemn the government, with President Trump warning Iranian leaders, via Twitter, "Do not kill your protesters" and "the world is watching." In May 2018, President Trump signed National Security Presidential Memorandum 11, "ceasing U.S. participation in the JCPOA [Joint Comprehensive Plan of Action] and taking additional action to counter Iran's malign influence and deny Iran all paths to a nuclear weapon." The action set in motion a reestablishment of U.S. unilateral economic sanctions that affect U.S. businesses and include secondary sanctions that target commerce originating in other countries that engage in trade with and investment in Iran. On January 10, 2020, the President, as promised in the immediate aftermath of the U.S. drone strike that killed Soleimani, announced new sanctions to curtail international trade, transactions, and financing in Iran's construction, mining, manufacturing, and textile sectors. The Secretary of the Treasury, on the same day, announced that eight "senior Iranian regime officials who have advanced the regime's destabilizing objectives" were made subject to sanctions, and 17 Iranian metals producers, mining companies, and three partners in China and the Seychelles that facilitated trade in Iran's metal products were also now designated for economic restrictions. The sanctions authority announced on January 10, like the authority used to target those engaged in Iran's metals and mining sectors, can be used to target individuals and entitiesâincluding financial institutionsâin third countries (secondary sanctions) that are found to operate in or engage in the sector, or materially assist, sponsor, or provide "financial, material, or technological support for, or goods or services to or in support of" any entity subject to sanctions for its participation in Iran's construction, mining, manufacturing, and textile sectors. Foreign financial institutions, in particular, could be subject to being denied the means to operate in the United States. No designations have been made yet under this new sanctions authority. Following the Trump Administration's May 2018 announcement that the United States would no longer participate in the JCPOA, Iran threatened to exceed the agreement's limits on the country's nuclear activities. In July 2019, the International Atomic Energy Agency (IAEA) verified that some of Iran's nuclear activities were exceeding these limits; the Iranian government has since increased the number of such activities, such as exceeding JCPOA-mandated limits on its heavy water stockpile. The Iranian government announced on January 5, 2020, what an official news agency report described as "the fifth and final step in reducing" Tehran's JCPOA commitments. The statement explains that Iran "will set aside the final operational restrictions under the JCPOA which is 'the restriction on the number of centrifuges,'" but provides no further details. Tehran has stated that the government will continue to cooperate with the IAEA and abide by the JCPOA's monitoring and inspections provisions. The January 5 announcement adds that "[i]n case of the removal of sanctions and Iran benefiting from the JCPOA," Iran "is ready to resume its commitments" pursuant to the agreement. This announcement does not mention Soleimani's death and is consistent with a timeline described in a November 5, 2019, speech by Iranian President Hassan Rouhani speech, in which he said, "In the next two months, we still have a chance for negotiations." Iran's support for armed factions in the region is a key instrument of its policy. Iran's operations in support of its allies (identified below) are carried out by the IRGC-QF, formerly headed by Soleimani. IRGC leaders generally publicly acknowledge operations in support of regional allies, although they often characterize Iran's support as humanitarian aid or protection for Shia minority populations or religious sites. Iran supplies weaponry to its allies including specialized anti-tank systems, artillery rockets, mortars, short-range ballistic missiles, and cruise missiles. Estimates of the dollar value of material support that Iran provides to its allies and proxies vary widely and are difficult to corroborate. Information from official U.S. government sources sometimes provides broad dollar figures without breakdowns or clear information on how those figures were derived. For example, the State Department's September 2018 report "Outlaw Regime: A Chronicle of Iran's Destructive Activities" asserts that Iran has spent over $16 billion since 2012 "propping up the Assad regime and supporting [Iran's] other partners and proxies in Syria, Iraq, and Yemen." However, that report appears to cite an outside estimate that does not explain how the estimates were derived. The State Department has described Hezbollah, a Lebanon-based militia and U.S.-designated Foreign Terrorist Organization (FTO) that plays a major role in Lebanese politics, as "Iran's primary terrorist proxy group;" Iran provides Hezbollah with significant funding, training and weapons. In June 2018, Treasury Under Secretary for Terrorism and Financial Intelligence Sigal Mandelker estimated that Iran provided Hezbollah with more than $700 million per year. According to the State Department, Iran provides Hezbollah with thousands of rockets, short-range missiles, and small arms, and has trained "thousands" of Hezbollah fighters at camps in Iran. Israeli security officials have also expressed concern that Iran may be assisting Hezbollah to develop an indigenous rocket and missile production capability. Since violence broke out in Syria in 2011, Iran has provided technical assistance, training, and financial support to both the Syrian government and to pro-regime Shia militias operating in Syria. The U.S. Department of the Treasury has designated for sanctions the Iranian Ministry of Intelligence and Security (MOIS), the IRCG-QF, and Iran's national police pursuant to Executive Order 13572 (April 2011), for assisting the Syrian government in its violent crackdown on protestors. Iran also has facilitated the travel of Shia militia fighters from Iraq, Afghanistan, and Pakistan into Syria to bolster the Asad government. Iran has directly backed the activities of these militia fighters with armored vehicles, artillery, and drones. Iran also has provided Syria with billions of dollars in credit to purchase oil, food, and import goods. In mid-2019, the United States imposed sanctions on Iranian ships and shipping facilitators involved in Iranian oil shipments to Syria. Iran supports a number of armed groups in Iraq, including U.S. designated terrorist organizations such as Kata'ib Hezbollah (KH), Asa'ib Ahl al Haq (AAH), and Harakat Hezbollah al Nujaba. Iran-linked groups in Iraq directly targeted U.S. forces from 2003 through 2011, and U.S. officials blame Iran-linked Iraqi groups for a series of indirect fire attacks on U.S. and Iraqi facilities hosting U.S. civilian and military personnel since 2018. The 115 th and 116 th Congresses have considered proposals directing the Administration to impose U.S. sanctions on some Iran-aligned Iraqi groups, and enacted legislation containing reporting requirements focused on Iranian support to nonstate actors in Iraq and other countries. On January 3, 2020, the State Department designated the AAH as a Foreign Terrorist Organization and two of the group's leaders, Qa'is Khazzali and his brother Laith, as Specially Designated Global Terrorists under E.O.13224, as amended by E.O. 13886. These designations follow action taken by the Department of the Treasury on December 6, 2019, to designate the brothers pursuant to E.O. 13818 for their involvement in serious human rights abuses in Iraq, notably approving lethal force against protestors. Several Iraqi militia forces have vowed revenge against the United States and stated their renewed commitment to expelling U.S. forces from Iraq, but some others have called for a measured approach and disavowed potential attacks on non-military targets as a means of fulfilling their stated objectives. For example, Kata'ib Hezbollah released a statement in the aftermath of the Iranian missile attack on Iraq saying "emotions must be set aside" to further the project of expelling the United States. On January 8, Qa'is al Khazali said that the response to the killing of Soleimani and Muhandis "will be no less than the size of the Iranian response. That is a promise." Later Khazali denied responsibility for a January 8 rocket attack targeting the U.S. Embassy while insisting on U.S. military withdrawal and vowing an "earthshattering" response. Iran has sometimes intervened militarily in Iraq directly, including by conducting air strikes against Islamic State forces advancing on the border with Iran in 2014 and by launching missiles against Iranian Kurdish groups encamped in parts of northern Iraq in 2018. Iranian leaders have not historically identified Yemen as a core Iranian security interest, but they have given some material support to the Shia Houthi rebels that are fighting Saudi Arabia and the coalition that it leads in support of the Yemeni government. In response to the Saudi-led air campaign in Yemen, the Houthis have fired ballistic missiles on sites within Saudi Arabia on several occasions; Saudi Arabia, with U.S. backing, accuses Iran of providing those missiles. The increasingly sophisticated nature of Iran's support for the Houthis could suggest that Iran perceives the Houthis as a potential proxy to project power on the southwestern coast of the Arabian Peninsula. On the other hand, Special Representative for Iran and Senior Advisor to the Secretary of State Brian Hook stated on December 5, 2019, that Iran's continued involvement in the conflict amidst a nascent Saudi-Houthi de-escalation process since September 2019 shows that "Iran clearly does not speak for the Houthisâ¦. Iran is trying to prolong Yemen's civil war to project power." In December 2019, the U.S. government offered up to $15 million for information concerning Yemen-based IRGC-QF leader Abdul Reza Shahla'i. Shahla'i reportedly was targeted by a strike or raid in Yemen on January 3, 2020, the day of Soleimani's killing. Unnamed U.S. officials reportedly confirmed the operation, which was unsuccessful, on January 10, leading some analysts and some Members of Congress to question the Administration's assertion that the Soleimani strike was justified by an "imminent threat." In addition to the entities above, the U.S. government alleges that Iran provides support to other regional groups, including Palestinian groups Hamas and Islamic Jihad, the Bahraini group Al Ashtar Brigades, and the Afghan Taliban. Iraqi officials protested the December 29 U.S. airstrikes on KH personnel as a violation of Iraqi sovereignty, and, days later, KH members and other figures associated with Iran-linked militias and PMF units marched to the U.S. Embassy in Baghdad and damaged property, setting outer buildings on fire. Iraqi officials and security forces reestablished order outside the embassy, but tensions remained high, with KH supporters and other pro-Iran figures threatening further action and vowing to expel the United States from Iraq by force if necessary. As noted, along with Soleimani, the U.S. airstrike that hit his convoy also killed KH founder and PMF leader Jamal Ja'far al Ibrahimi (commonly referred to as Abu Mahdi al Muhandis). Muhandis was one of the key Iraqi leaders aligned with Iran who worked with Soleimani to develop and maintain Iran's ties to armed groups in Iraq over the last 20 years; Soleimani long served as a leading Iranian emissary to Iraqi political and security figures. The death of Al Muhandis is expected to require renegotiation in the relationships among Iran-aligned Iraqi militias and shape the PMF's future. The U.S. operation was met with shock in Iraq, and Prime Minister Adel Abd al Mahdi and President Barham Salih issued statements condemning the strike as a violation of Iraqi sovereignty. The prime minister called for and then addressed a special session of Iraq's unicameral legislature, the Council of Representatives (COR), on January 5, recommending that the quorum of legislators present vote to direct his government to ask all foreign military forces to leave the country. Most Kurdish and Sunni COR members reportedly boycotted the session. Those COR members present adopted by voice vote a parliamentary decision directing the Iraqi government to withdraw its request to the international anti-IS coalition for military support; remove all foreign forces from Iraq and end the use of Iraq's territory, waters, and airspace by foreign militaries; protest the U.S. airstrikes as breaches of Iraqi sovereignty at the United Nations and in the U.N. Security Council; and investigate the U.S. strikes and report back to the COR within seven days. On January 6, Prime Minister Abd al Mahdi met with U.S. Ambassador to Iraq Matthew Tueller and informed him of the COR's decision, requesting that the United States begin working with Iraq to implement the COR decision. In a statement, the prime minister's office reiterated Iraq's desire to avoid war, to resist being drawn into conflict between outsiders, and to maintain cooperative relations with the United States based on mutual respect. Amid subsequent reports that some U.S. military forces in Baghdad are repositioning for force protection reasons and potentially "to prepare for onward movement," Secretary Esper stated, "There has been no decision made to leave Iraq, period." On January 9, Prime Minister Abd al Mahdi asked Secretary of State Michael Pompeo to "send delegates to Iraq to prepare a mechanism to carry out the parliament's resolution regarding the withdrawal of foreign troops from Iraq." On January 10, the State Department released a statement saying "At this time, any delegation sent to Iraq would be dedicated to discussing how to best recommit to our strategic partnership, not to discuss troop withdrawal, but our right, appropriate force posture in the Middle East." Secretary of State Michael Pompeo said that Prime Minister Abd al Mahdi's office had not characterized their conversation accurately, and said We are happy to continue the conversation with the Iraqis about what the right structure is. Our mission set there is very clear: We've been there to perform a training mission to help the Iraqi security forces be successful and to continue the campaign against ISIS, the counter-Daesh campaign. We're going to continue that mission. But as theâas times change and we get to a place where we can deliver upon what I believe and the President believes is our right structure, with fewer resources dedicated to that mission, we will do so. Prime Minister Abd al Mahdi's December 2019 resignation marked the beginning of what may be an extended political transition period in Iraq that reopens several contentious issues for debate and negotiation. Principal political decisions now before Iraqi leaders concern (1) identification and endorsement of a caretaker prime minister and cabinet, (2) implementation of adopted electoral system reforms, and (3) the proposed holding of parliamentary and provincial government elections in 2020. Following any national elections, government formation negotiations would recur, taking into consideration domestic and international developments over the interim period, including the fate of foreign military efforts in Iraq and the state of U.S.-Iran-Iraq relations. Leaders in Iraq's Kurdistan Regional Government have endorsed the continuation of foreign military support for Iraq, but may be wary of challenging the authority of the national government if Baghdad issues departure orders to foreign partners. On January 7, Kurdistan Democratic Party leader and former KRG President Masoud Barzani said, "we cannot be involved in any proxy wars." Prime Minister Abd al Mahdi traveled to Erbil to consult with Barzani on January 11, generating speculation that Abd al Mahdi may be seeking support for a re-nomination as prime minister. In 2014, the Iraqi government submitted two requests to the United Nations Security Council asking for international training, advice, and military assistance in combatting the threats posed by the Islamic State organization. These invitational letters have provided the underlying diplomatic basis for the presence of most U.S. and other international military forces in Iraq since 2014. Supplementary bilateral agreements between the Iraqi government and troop contributing countries set terms for the continued deployment of foreign forces in Iraq, and the presence of U.S. troops contributing to Operation Inherent Resolve (the U.S.-led international coalition to defeat the Islamic State), related training, and advisory support is governed by an exchange of diplomatic notes agreed to in 2014. According to former Special Presidential Envoy for the Global Coalition to Counter ISIL Brett McGurk, the 2014 U.S.-Iraq diplomatic notes, which are not public, contain a one year cancelation clause. The executive authority of the Iraqi government (the Prime Minister) may seek to amend or revoke requests for international assistance submitted to the United Nations or reached with other governments at its discretion: Iraq's constitution does not require the Iraqi executive to seek the approval of legislators in the Council of Representatives. As noted above, Prime Minister Abd al Mahdi and Secretary of State Pompeo have had initial conversations regarding the future of the U.S. presence in Iraq. President Trump has threatened to impose sanctions on Iraq, if Iraq forces U.S. troops to withdraw on unfriendly terms. Depending on the form such sanctions might take, they could elicit reciprocal hostility from Iraq and could complicate Iraq's economic ties to its neighbors and U.S. partners in Europe and Asia. If denied opportunities to build economic ties to the United States and U.S. partners, Iraqi leaders could instead mover closer to Iran, Russia, and/or China with whom they have already established close ties. Since 2018, Iraqi leaders have sought and received temporary relief from U.S. sanctions on Iran, in light of Iraq's continuing dependence on purchases of natural gas and electricity from Iran. The Trump Administration has serially granted temporary permissions for these transactions to continue, while encouraging Iraq to diversify its energy relationships with its neighbors and to become more energy independent. The Administration's most recent such sanction exemption for Iraq is set to expire in February 2020. Some press reporting suggests that Administration officials have begun preparing to implement the President's sanctions threat if necessary and considering potential effects and consequences. On May 19, 2019, the Trump Administration renewed the national emergency with respect to the stabilization of Iraq declared in Executive Order 13303 (2003) as modified by subsequent executive orders. Sanctions could be based on the national emergency declared in the 2003 Executive Order, or the President could declare that recent events constitute a new, separate emergency under authorities stated in the National Emergency Act and International Emergency Economic Powers Act (NEA and IEEPA, respectively). Sanctions under IEEPA target U.S.-based assets and transactions with designated individuals; while a designation might not reap significant economic disruption, it can send a significant and purposefully humiliating signal to the international community about an individual or entity. The National Emergencies Act, at 50 U.S.C. 1622, provides a legislative mechanism for Congress to terminate a national emergency with enactment of a joint resolution of disapproval. Short of declaring a national emergency, however, the President has broad authority to curtail foreign assistance (throughout the Foreign Assistance Act of 1961 (22 U.S.C. 2151 et seq.), and related authorizations and appropriations), sales and leases of defense articles and services (particularly Section 3 of the Arms Export Control Act; 22 U.S.C. 2753), and entry into the United States of Iraqi nationals (Immigration and Nationality Act; particularly at 8 U.S.C. 1189). More than 5,000 U.S. military personnel and hundreds of international counterparts remain in Iraq at the Iraqi government's invitation, subject to bilateral executive-to-executive agreements. Since Soleimani's death, Canada and Germany have announced withdrawal of some of their training forces from Iraq. Combined Joint Task ForceâOperation Inherent Resolve (CJTF-OIR) announced on January 5 that U.S. training and counter-IS operations were being temporarily paused to enable U.S. forces to focus on force protection measures. U.S. officials have reported that through October 2019, the Islamic State group in Iraq continued "to solidify and expand its command and control structure in Iraq, but had not increased its capabilities in areas where the Coalition was present." CJTF-OIR judged that IS fighters "continued to regroup in desert and mountainous areas where there is little to no local security presence" but were "incapable of conducting large-scale attacks." Iraqi Security Forces (ISF), Counter Terrorism Service (CTS) and Popular Mobilization Forces (PMF) continue to conduct clearance, counterterrorism, and hold missions against IS fights across northern, central, and western Iraq. Some of these operations are conducted without U.S. and coalition support, while others are partnered with U.S. and coalition forces or supported by U.S. and coalition forces. In its latest public oversight reporting, CJTF-OIR described the Iraqi Security Forces as lacking sufficient personnel to hold and constantly patrol remote terrain. According to CJTF-OIR reporting to the DOD inspector general, Iraq's Counterterrorism Service (CTS) has "dramatically improved" its ability "to integrate, synchronize, direct, and optimize counterterrorism operations," and some CTS brigades are able to sustain unilateral operations. According to U.S. officials, ISF units are capable of conducting security operations in and around population centers and assaulting identified targets but many lack the will and capability to "find and fix" targets or exploit intelligence without assistance from coalition partners. According to November 2019 reporting CJTF-OIR said that most commands within the ISF will not conduct operations to clear ISIS insurgents in mountainous and desert terrain without Coalition air cover, intelligence, surveillance, and reconnaissance (ISR), and coordination. Instead, ISF commands rely on the Coalition to monitor "points of interest" and collect ISR for them. Despite ongoing training, CJTF-OIR said that the ISF has not changed its level of reliance on Coalition forces for the last 9 months and that Iraqi commanders continue to request Coalition assets instead of utilizing their own systems. These conditions and trends suggest that while the capabilities of IS fighters remain limited at present, IS personnel and other armed groups could exploit persistent weaknesses in ISF capabilities to reconstitute the threats they pose to Iraq and neighboring countries. This may be particularly true with regard to remote areas of Iraq or under circumstances where security forces remain otherwise occupied with crowd control or force protection measures. A reconstituted IS threat might not reemerge rapidly under these circumstances, but the potential is evident. U.S. and coalition training efforts have shifted to a train-the-trainer and Iraqi ownership approach under the auspices of OIR's Reliable Partnership initiative and the NATO Training Mission in Iraq. Reliable Partnership was redesigned to focus on building a minimally viable counterterrorism capacity among Iraqi forces, with other outstanding capability and support needs to be reassessed after September 2020. In the days following the Soleimani killing, Coalition and NATO training efforts were temporarily suspended, and some countries announced plans to withdraw forces participating in Coalition and NATO training programs. If such trends continue, they could accelerate an already planned transition to greater Iraqi ownership of training efforts and an international reassessment of Iraq's needs and terms for longer-term partnership. The January 5 CJTF-OIR statement that announced the pause in counter-IS operations in Iraq following Soleimani's death, referenced above, did not mention the status of U.S. operations against the Islamic State in Syria, where roughly 600 U.S. forces are currently based. Various observers have argued that the absence of ongoing U.S. counterterrorism pressure is likely to provide the Islamic State with the operational space necessary to reconstitute itself in the region. U.S. forces in Syria have at times come into direct conflict with Iran-backed militia forces. In 2017, U.S. forces in Syria conducted strikes against pro-Asad militia fighters that infiltrated the de-confliction area around the U.S. garrison at At Tanf. In late 2019, U.S. forces targeted the Iran-backed militia Kata'ib Hezbollah in Iraq and eastern Syria, in response to an attack by the group on U.S. forces in Kirkuk. U.S. personnel in Syria may be vulnerable to additional attacks by Iran-backed forces. On January 4, 2020, President Trump submitted a notification to the Speaker of the House and President Pro Tempore of the Senate of the Soleimani drone strike, as required by Section 4(a) of the War Powers Resolution ( P.L. 93-148 ; 50 U.S.C. Â§ 1543(a)(1)), which requires notification within 48 hours of U.S. forces being introduced into conflict or into a situation that could lead to conflict. That notification, pursuant to the War Powers Resolution, also is to set out the constitutional and legislative authority for the action. According to a media report, citing "congressional officials," the notification was classified in its entirety by the Trump Administration, and its contents therefore have not been made publicly available. Speaker Nancy Pelosi criticized the decision to classify the notification in its entirety as "highly unusual." In statements after the strike, National Security Adviser Robert O'Brien asserted that the Authorization for Use of Military Force Against Iraq Resolution of 2002 ("2002 AUMF"; P.L. 107-243 ) provided the President authority to direct the strike against General Soleimani in Iraq. Congress enacted the 2002 AUMF prior to the 2003 U.S. invasion of Iraq that toppled the government of Saddam Hussein, authorizing the President to use the U.S. military to enforce United Nations Security Council resolutions targeting the Hussein regime and to "defend the national security of the United States against the continuing threat posed by Iraq." The Obama Administration had asserted that U.S. military action after 2014 against the Islamic State in Iraq and Syria was authorized pursuant to the 2002 AUMF as well as the post-September 11, 2001 Authorization for Use of Military Force ("2001 AUMF"; P.L. 107-40 ). In a March 2018 report to Congress, the Trump Administration argued that the 2002 AUMF "has always been understood to authorize the use of force for the related dual purposes of helping to establish a stable, democratic Iraq and for the purpose of addressing terrorist threats emanating from Iraq." Speaking in the context of the campaign against the Islamic State, the report stated that the 2002 AUMF "contains no geographic limitation," and asserted that the statute permits the use of military force to protect Iraq outside the territory of Iraq itself if necessary. In a June 2019 letter, the State Department explained that it determined that 2002 AUMF authority permitted the use of military force against Iran "as may be necessary to protect U.S. and partner forces engaged in counterterrorism operations or operations to establish a stable, democratic Iraq." To the extent the Administration considers the actions of Soleimani and the IRGC (designated by President Trump in April 2019 as a terrorist organization) as creating a threat to Iraq's stability or a threat of terrorism, as well as a necessity to protect U.S. or partner forces, this interpretation of the 2002 AUMF would seem to authorize operations such as the Soleimani drone strike both within and outside Iraq. Reaction from Members of Congress to the drone strike has been divided, with some Members praising the decision as a blow to Iran's operations placing U.S. and partner forces at risk of attack, and others criticizing the President's decision as possibly precipitating armed conflict between the United States and Iran, and increasing the risk of broader instability in the Middle East. Some Members, including Speaker Nancy Pelosi, have decried the President's failure to inform and consult with Congress prior to the strike, and have questioned the President's authority to conduct such military action. In response to the strike, Senators Tim Kaine and Richard Durbin introduced a joint resolution ( S.J.Res. 63 ) to "direct the removal of United States Armed Forces from hostilities against the Islamic Republic of Iran that have not been authorized by Congress." The resolution states that neither the 2002 AUMF nor the 2001 AUMF provide specific authority to the President to use military force against Iran, and that Congress has not provided such specific authority in any legislation. The resolution further finds that there exists a "conflict between the United States and the Islamic Republic of Iran" that constitutes, pursuant to Section 4(a)(1) of the War Powers Resolution ( P.L. 93-148 ; 50 U.S.C. Â§ 1543(a)(1)), "hostilities or a situation where imminent involvement in hostilities is clearly indicated by the circumstances," into which U.S. armed forces have been introduced without authorization. The resolution therefore directs the President to remove U.S. armed forces from hostilities with Iran, "or any part of its government or military," within 30 days of the resolution's enactment. The resolution was introduced pursuant to Section 1013 of the Department of State Authorization Act, Fiscal Years 1984 and 1985 (50 U.S.C. Â§ 1546a), which permits expedited consideration in the Senate of a joint resolution that "requires the removal of United States Armed Forces engaged in hostilities" without specific congressional authorization. On January 7, 2020, Representative Ilhan Omar introduced H.J.Res. 82 , the text of which is identical to S.J.Res. 63 . After indicating that he had agreed to some changes to S.J.Res. 63 , Senator Kaine introduced an amended version of his original proposal, S.J.Res. 68 , on January 9, 2020. Instead of directing the President to "remove" U.S. armed forces from hostilities with Iran, S.J.Res. 68 would direct the President to "terminate the use of U.S. armed forces for hostilities" with Iran. This change might be a reflection of concern that requiring "removal" of U.S. armed forces might precipitate changes in current deployments, including possible withdrawal of U.S. armed forces in Iraq. The new proposal also eliminates references to Trump Administration statements and policy with regard to Iran. On January 3, 2020, Representative Ro Khanna and Senator Bernie Sanders indicated their intent to introduce legislation to prohibit funding for the U.S. use of military force against Iran. Representative Khanna introduced his bill, H.R. 5543 , with 47 cosponsors, on January 7. The bill would state that neither the 2002 AUMF nor 2001 AUMF, nor any other existing provision of law, may be construed to provide authority to use military force against Iran, and would prohibit the use of federal funds to use force against Iran without such specific authorization. The proposed legislation is identical to an amendment adopted in the House version of the National Defense Authorization Act for Fiscal Year 2020, but that was not included in the final version of the act. Senator Sanders introduced a similar bill, S. 3159 , on January 8, 2020. On January 8, 2020, Senator Jeff Merkley introduced S.J.Res. 64, which consists of a provision specifying that neither the Authorization for Use of Military Force Against Iraq Resolution of 2002 ("2002 AUMF"; P.L. 107-243 ), nor the post-September 11, 2001 Authorization for Use of Military Force ("2001 AUMF"; P.L. 107-40 ) "may be interpreted as a statutory authorization for the use of military force against the Islamic Republic of Iran." On January 8, 2020, Representative Elissa Slotkin introduced, pursuant to Section 5(c) of the War Powers Resolution (50 U.S.C. Â§ 1544(c)), a concurrent resolution ( H.Con.Res. 83 ) "to terminate the use of United States Armed Forces to engage in hostilities in or against Iran." This resolution would state that Congress has not enacted an authorization for the President to use military force against Iran, and that any decision to use force against Iran should be explained both to Congress, as required by Section 3 of the War Powers Resolution, and the American people. It explains, however, that the "United States has an inherent right to self-defense against imminent armed attacks." In the operative provision, it would therefore directs the President "to terminate the use of United States Armed Forces to engage in hostilities in or against Iran or any part of its government or military," unless Congress specifically authorizes such use of the armed forces, or if such force is necessary and appropriate to defend the United States or its armed forces against "imminent attack." Senator Tom Udall introduced a companion resolution in the Senate, S.Con.Res. 33 , on January 9, 2020. The House debated H.Con.Res. 83 on January 9, 2020. During debate, proponents of the resolution argued that the President had taken military action that made wider conflict with Iran more likely, and that it was the constitutional duty of the Congress to require the President to obtain specific legislative authorization for any further military action against Iran only after the Congress had a full opportunity to debate such authorization. Opponents of the measure stated that the President's strike on Soleimani was lawful and necessary to protect the national security of the United States and the safety of U.S. armed forces in Iraq and the Middle East region, and that congressional action to limit the President from carrying out further military action was divisive and would embolden Iran and other enemies of the United States. After general debate, the House voted to adopt H.Con.Res. 83 by a 224-194 roll call vote. The measure will now move to the Senate, where it is to be referred to the Senate Foreign Relations Committee. As a Section 5(c) concurrent resolution receiving privileged consideration pursuant to Section 7 of the War Powers Resolution (50 U.S.C. Â§ 1546), the Committee is required to report the measure to the full Senate for consideration no later than 15 calendar days after referral, upon which the measure becomes the pending business of the Senate and shall be voted upon in the Senate within three calendar days, unless the Senate votes to alter the timeframe by the yeas and nays. Regarding concurrent resolutions. H.Con.Res. 83 was introduced pursuant to Section 5(c) of the War Powers Resolution (50 U.S.C. Â§ 1544(c)), which sets out a process by which Congress can direct termination of an unauthorized presidential use of military force through concurrent resolution, adopted in both houses of Congress but not presented to the President for signature. It has been argued that this provision constitutes an unconstitutional "legislative veto," essentially a legislative action that is intended to have the effect of enacted law but without the step of presentment to the President. In invalidating an unrelated statute as constituting a "legislative veto," the Supreme Court in INS v. Chadha determined that all "legislative acts" are subject to the bicameralism and presentment requirements of Article I, Â§7. The Court defined a legislative act as any action "properly [] regarded as legislative in its character and effect" or taken with "the purpose and effect of altering the legal rights, duties and relations of persons ... outside the Legislative Branch." The courts, however, have not ruled expressly on the constitutionality of Section 5(c), and it is not settled that Section 5(c) resolutions necessarily involve congressional reversal of executive branch action by a simple or concurrent resolution, when such decisions were taken pursuant to a previous congressional delegation of authority to such agency by legislation. It could be argued that Congress adopting a concurrent resolution directing withdrawal from unauthorized hostilities is not a legislative act to repeal existing authority previously delegated by Congress. Congress in the War Powers Resolution has not purported to delegate use of military force decision making authority to the President, setting a legislative veto to reverse such decisions when it sees fit. Nor has it delegated authority to the President to order any specified use of military force. Instead, it can be argued that Congress is indicating its will to formally disapprove an originally unauthorized use of military force, which arguably would not alter the legal rights or duties of the President. Such a resolution would act to reiterate Congress's position, stated in Section 2 of the War Powers Resolution, that the Constitution grants only Congress, not the President, the authority to introduce U.S. armed forces into hostilities in all cases except defense against an armed attack on the United States, its possessions, or U.S. armed forces. Regarding Joint Resolutions. A concurrent resolution evidencing the will of Congress to direct the President to withdraw from hostilities that the War Powers Resolution asserts is already unauthorized may nonetheless have less than the desired effect, as it is in one conception merely a reiteration of congressional interpretation of the limits of presidential war powers, an interpretation already rejected in most instances by the President. Using a joint resolution rather than a concurrent resolution as a vehicle to direct the President to cease action against Iran, S.J.Res. 63 (for example) was introduced under Section 1013 of the Department of State Authorization Act, Fiscal Years 1984 and 1985 (50 U.S.C. Â§ 1546a). Congress enacted Section 1013 in the wake of the Chadha decision to provide a separate process by which Congress could expedite consideration of a joint resolution that would require presentment to the President rather than using an expedited Section 5(c) resolution. Utilization of this provision might be preferred by some Members of Congress, as it avoids the legislative veto issue, and perhaps provides a more forceful vehicle by which to require an end to unauthorized presidential introduction of U.S. armed forces into hostilities. On the other hand, such joint resolutions presented to the President are likely to receive a presidential veto, requiring two-thirds majorities in both Houses if such resolutions are to become law. This was a situation Congress sought to avoid when enacting the War Powers Resolution, as it placed a severe test on Congress to act to preserve its role in determining whether the United States would enter a military conflict. Secretary Pompeo has said that although U.S. personnel in the Middle East are safer following the removal of Soleimani from the battlefield, there remains "an enormous set of risks in the region" and that the United States is "preparing for each and every one of them." Secretary Pompeo has also remarked that the United States will ensure that its overseas diplomatic facilities are as "hardened as we can possibly get them" to defend against possible Iranian action. Following the December 31 blockade of the U.S. Embassy in Baghdad, 100 Marines assigned to the Special Purpose Marine Air-Ground Task Force, Crisis ResponseâCentral Command (SPMAGTF-CR-CC) were deployed at the State Department's request to reinforce the Embassy. Analysts note that this Task Force, which was created after the 2012 attack on a U.S. post in Benghazi, is capable of providing compound defense through the use of air, ground, and, when necessary, amphibious operations. These additional forces augment the Marine Security Guard (MSG) detachment and other security personnel already present at the Embassy. MSGs have worked with the State Department to protect and safeguard U.S. overseas posts for over 60 years. Neither the State Department nor the Department of Defense disclose the number of MSGs serving at each overseas post. General Milley has expressed confidence regarding Embassy Baghdad's security, stating that it is unlikely to be overrun and warning that air and ground capabilities there mean that anyone who attempts to do so "will run into a buzzsaw." Some analysts maintain that because Iran and its proxies have previously demonstrated their capability to perpetrate attacks throughout the world, the State Department must mitigate risks to the safety of U.S. personnel not only in the Middle East but worldwide. State Department regulations enable the Principal Officer at each overseas post (at an embassy, this would be the ambassador), Regional Security Officer (or RSO, the senior Diplomatic Security Service special agent serving at post), and the post's Emergency Action Committee, with the support of Bureau of Diplomatic Security personnel in Washington, DC, to evaluate threats and develop and implement security policies and programs. Some analysts have suggested that past Iranian behavior indicates that the State Department should give special consideration to the threat posed by kidnapping or attacks focused on so-called "soft targets," which include buildings such as schools, restaurants, or other public spaces that often are frequented by diplomats or their families. The State Department could also choose to close or change the status of an overseas post in response to evolving threat assessments. This occurred previously in Iraq, when in September 2018 the State Department announced that the U.S. Consulate General in Basrah would be placed on ordered departure, meaning that all U.S. personnel would be evacuated from post. Secretary Pompeo has stated that the State Department is continuing to evaluate the appropriate overseas diplomatic posture for the United States given the Iranian threat. As policymakers and analysts consider how Iran might respond to the killing of Soleimani, the situation clearly has implications for the state of Israel. Israel and Iran are already engaged in low-level conflict. Since 2017, this has reportedly included periodic cross-border exchanges of fire between Israel and Iran-supported groups in Syria and Lebanon, as well as numerous Israeli air strikes against Iran-linked targets in both countries and Iraq. Israel has indicated that Iranian transfers of precision-guided rockets and missiles to groups, such as Hezbollah in Lebanon, and Iran's presence in Syria, have made the situation on its northern front one of the top threats to Israel's national security (alongside Iran's nuclear program). As a result of Soleimani's killing, the Israel Defense Forces have been placed on high alert. Israel has an extensive network of missile defense systems, and Congress annually appropriates funds for joint U.S.-Israeli missile defense research, development, and production. On January 6, the United States Embassy in Israel released a travel advisory, warning of the possibility of rocket fire against the country. However, that same day, senior Israeli military officials held a security cabinet meeting in which they expressed doubt that Iran would target Israel. Prime Minister Binyamin Netanyahu praised President Trump in connection with Soleimani's killing, stating, "Just as Israel has the right of self-defense, the United States has exactly the same right." Beyond Israel, there is some concern that Iran could retaliate against Jewish targets worldwide. In 1994, 85 people were killed in a bombing of a Jewish community center in Buenos Aires, Argentina. In 2012, a suicide bomber killed five Israeli tourists in Bulgaria. Various sources have linked Hezbollah and Iran to these attacks. Differences over Iran have strained U.S.-European relations during the Trump Administration. The EU opposes the Administration's decision to withdraw from the JCPOA, and has sought to work with Iran and other signatories to prevent its collapse. The EU shares other U.S. concerns about Iran, however, including those related to Iran's ballistic missile program and support for terrorism. On January 6, 2020, French President Emmanuel Macron, German Chancellor Angela Merkel, and UK Prime Minister Boris Johnson released a joint statement asserting that We have condemned the recent attacks on coalitions [sic] forces in Iraq and are gravely concerned by the negative role Iran has played in the region, including through the IRGC and the Al-Qods force under the command of General Soleimani. There is now an urgent need for de-escalation. We call on all parties to exercise utmost restraint and responsibility. The current cycle of violence in Iraq must be stopped. We specifically call on Iran to refrain from further violent action or proliferation, and urge Iran to reverse all measures inconsistent with the JCPOA. The statement additionally expressed concern about security and stability in Iraq and emphasized the importance of continuing to combat the Islamic State. In a subsequent statement following a meeting of NATO countries, NATO Secretary General Jens Stoltenberg reiterated many of these points, similarly expressing concern about Iran's destabilizing behavior and calling for de-escalation. European countries are significant contributors to Global Coalition to Defeat ISIS and the NATO training and advisory mission in Iraq, both of which suspended operations following the Soleimani strike. Germany and several other European nations reportedly began moving troops out of Iraq in the days after Soleimani's death. Additionally, in recent years, European countries have stepped up criticism of Iran for alleged Iranian plots to assassinate dissidents in Europe. The U.S. State Department said in a 2018 report that Iranian-sponsored terrorist attacks in Europe, after a "brief lull in the 1990s and early 2000s," are "on the rise." In January 2019, in response to a Dutch letter linking Iran to assassinations of Dutch nationals of Iranian origin in 2015 and 2017, the EU imposed sanctions on the internal security unit of Iran's Intelligence ministry and two Iranian operatives for sponsoring acts of terrorism. Since May 2019, the United States has added forces and military capabilities in the region, beginning with the accelerated deployment of the USS Abraham Lincoln (which was relieved in December 2019 by the USS Harry S. Truman Carrier Strike Group). The additional deployments as of October 2019 had added approximately ten thousand U.S. military personnel to a baseline of between 60,000-80,000 U.S. forces in and around the Persian Gulf, which include those stationed at military facilities in the Arab states of the Gulf Cooperation Council (GCC: Saudi Arabia, Kuwait, UAE, Qatar, Oman, and Bahrain), and those in Iraq and Afghanistan. DOD officials indicated that the additional deployments are prudent defensive measures, allowing the U.S. to respond to aggression, if necessary. Other key recent deployments include the following: On December 31, 2019, DOD announced deployment to Kuwait of an infantry battalion from the Immediate Response Force (IRF) of the 82 nd Airborne Division, with 750 soldiers to deploy immediately and additional forces from the IRF (about 3,000 military personnel) to deploy thereafter. A small (likely platoon-size) element of the 173 rd Brigade is also deploying to the region, possibly to Lebanon. On January 5, 2020, DOD officials announced that a task force of U.S. Special Operations Forces, including Rangers, was deployed to the Middle East. On January 6, 2020, reports indicated that the 26 th Marine Expeditionary Unit was being directed to the Mediterranean. On January 6, 2020, it was reported that DOD would be sending six B-52 Stratofortress bombers to Diego Garcia in the Indian Ocean, to be available for operations in Iran, if ordered. According to key Trump Administration documents, including the 2017 National Security Strategy and 2018 National Defense Strategy, effectively competingâeconomically, diplomatically, and militarilyâwith China and Russia is the key national security priority facing the United States today. Accordingly, activities that can bolster the United States within this competition are, at least in theory, to be prioritized over other strategic challenges including countering violent extremist groups, a long-standing and critical challenge in the CENTCOM area of responsibility (AOR). Some observers contend that a shift in U.S. resources away from the CENTCOM AOR and towards Europe and Asia is therefore necessary. CENTCOM Commander General Kenneth McKenzie noted in his questions for the record associated with his December 2018 confirmation hearing: The 2018 National Defense Strategy (NDS) will reduce U.S. force posture in the Central Region and realign resources to goals with higher priority in the NDS. The shift of U.S. resources away from USCENTCOM presents a challenge to the command's ability to provide deterrence with forward stationed combat credible forces. This will require USCENTCOM to develop new concepts and strengthen its relationships with regional partners and allies. Additionally, reduced U.S. presence provides an opportunity for competitors to potentially increase their influence with our partners. As stated earlier, this creates increased risk if USCENTCOM also loses funding which will likely be taken from engagement and security cooperation programs necessary to offset our reposturing-both real and perceived. Despite this intended strategic reprioritization, Iran has long been viewed as a central challenge to the United States and U.S. allies and interests in the CENTCOM AOR. General McKenzie argued in his confirmation hearing that "The long term, enduring most significant threat in the U.S. CENTCOM AOR is Iran," which will "require [CENTCOM] to adopt innovative new techniques to maintain deterrence against Iran, becauseâ¦the underpinning of everything else that will go on in the theater is the ability to deter Iran and respond if required to." These developments have led some observers to question whether the proposed strategic reprioritization of threats, including the redirection of assets and capabilities away from the CENTCOM AOR, is feasible. Others contend that despite recent developments with Iran, the region should still figure as a less important U.S. strategic priority given the scale of the challenges posed by China and Russia. Still others contend that force planning concepts like Dynamic Force Employmentâthat is, the rapid and unpredictable shift of key U.S. military assets from one theater to anotherâmitigate some of the risk associated with diverting resources away from CENTCOM. While the commitment of additional U.S. troops has been relatively modest since May 2019, other threats and contingencies could create a demand for additional U.S. forces that is not currently forecasted and that could create pressures on the U.S. military. Ultimately, any troops that are deployed to CENTCOM, as well as those training to replace them, would be taken out of the "pool" of forces available and ready to respond to other possible contingencies. U.S. military forces are a finite resource; the deployment of assets to the CENTCOM AOR would necessarily impact the availability of forces for other theaters and contingencies. U.S. expeditionary operations are enabled by a network of American bases and facilities that are hosted in other allied and partner countries. Yet basing of U.S. troops on foreign soil is a sensitive matter for host countries due to the fact that such deployments of American military forcesâwhich are subject to U.S. rather than host nation legal jurisdictionâare inherently in tension with a host nation's sovereignty. As a result, the political-military dynamics with the countries that host U.S. troops require careful management. Recent events, including the Soleimani strike and Iranian counter-strikes, could complicate bilateral negotiations on U.S. forward bases, both in Iraq as well as in other parts of the world, discussions that are already sensitive due to burden-sharing issues. While the aftermath of the January 8, 2020, Iranian missile counterstrikes is still evolving, many practitioners and experts note that the United States has, at times in recent decades, engaged in hybrid, irregular conflict with Iran (with U.S.-Iran naval clashes during the 1980-1988 Iran-Iraq War being a notable exception). Hybrid and irregular warfare are commonly understood to be instances in which belligerents, to varying extents, collaborate with proxies (including, but not limited to, militias, other countries, criminal networks, corporations, and hackers) and deliberately sow confusion as to what constitutes "civilian" versus "military" activities in order to create plausible deniability for a given action. Some scholars maintain that Iran relies heavily on proxy forces to achieve its objectives: [Iran's nonstate] network is the cornerstone of Iranian national security strategyâ¦ It is in large part because of this extensive network that the United States considers Iran a threat to national security and a destabilizing force in the region. Iran's network of nonstate partners enables the country to project power and increase its influence outside its borders while antagonizing the United States and its regional partners. In turn, these groups pursue a range of malign activities to sow instability, complicate ongoing conflicts, and undermine the interests of the United States and its partners, all while remaining under the threshold of warâwhich Tehran tries to avoid at all costs as its conventional forces lack the capabilities to match those of the United States. Many observers expect that U.S.-Iranian conflict will return to a state of mostly irregular/hybrid warfare. However, given the Trump Administration's overall strategic guidance to prioritize great power competition, some are concerned that insufficient attention and resources are now being dedicated toward preparing U.S. forces to wage the kind of irregular/hybrid warfare that may be an enduring feature of strategic dynamics, both in the Persian Gulf and in other parts of the world. Still others express concern that other national security and foreign policy institutions such as the State Departmentâwith nonmilitary capabilities and authorities that could be useful for effectively prosecuting U.S. irregular /hybrid warfare strategies (as well as countering such tactics from adversaries)âare insufficiently organized and resourced relative to the scope and scale of the challenges. 
The January 2, 2020, U.S. killing in Iraq of Islamic Revolutionary Guard Corps-Qods Force (IRGC-QF) Commander Qasem Soleimani, generally regarded as one of the most powerful and important officials in Iran, has potentially dramatic implications for the United States. For Congress, it raises possible questions about U.S. policy in the Middle East, broader U.S. global strategy, U.S. relations with partners and allies, the authorization and legality of U.S. military action abroad, U.S. measures to protect its servicemembers and diplomatic personnel, and congressional oversight of these and related issues. This report provides background information in response to some frequently asked questions related to the strike and its aftermath, including Who was Qasem Soleimani and why did the U.S. military kill him? How have Iranians reacted? How have Iraqis reacted and how does this impact Iraqi policy and government formation? How might the strike and Iraqi reactions impact the U.S. military presence in Iraq and the U.S.-led counter-ISIS campaign (Operation Inherent Resolve)? How does the killing of Soleimani impact Israel and its security? What has been the European reaction? Under what authority did the U.S. military carry out the strike? How have Members of Congress responded legislatively or otherwise? What is the U.S. force posture in the region? How do recent regional developments align with broader U.S. strategy? The information contained in this report, which will be updated periodically as events warrant, is current as of January 13, 2020. The following CRS products provide additional background and analysis of issues discussed in this report: CRS Report R44017, Iran's Foreign and Defense Policies , by Kenneth Katzman; CRS Report R45795, U.S.-Iran Conflict and Implications for U.S. Policy , by Kenneth Katzman, Kathleen J. McInnis, and Clayton Thomas; CRS In Focus IF11403, The 2019-2020 Iran Crisis and U.S. Military Deployments , by Kathleen J. McInnis; CRS In Focus IF10404, Iraq and U.S. Policy , by Christopher M. Blanchard; CRS Report R42699, The War Powers Resolution: Concepts and Practice , by Matthew C. Weed; CRS Report RL34544, Iran's Nuclear Program: Status , by Paul K. Kerr; and CRS In Focus IF11338, Diplomatic Security and the Role of Congress , by Cory R. Gill and Edward J. Collins-Chase.