Iran–Iraq relations (Persian: روابط ایران و عراق Ravâbete Irân va Arâq; Arabic: العلاقات العراقية الإيرانية Al-ilaqat Al-Iraqiya Al-Iraniya) are the diplomatic and foreign relations between the two sovereign states of Iran and Iraq. Both States have history that extends for millennia into the past. Iran and Iraq share a long border (the longest border for both nations) and an ancient cultural and religious heritage. In ancient times Iraq formed part of the core of Persia (modern-day Iran) for about a thousand years. Modern relations between the two nations turned increasingly negative following the 14 July Revolution in Iraq in 1958, and subsequent overthrow of the Hashemite Monarchy which resulted in the country withdrawing from the Baghdad Pact. The Ba'ath Party gained power in Iraq in the 1960s, taking a more aggressive stance on border disputes. In the aftermath of the Islamic revolution in Iran in 1979, Saddam Hussein launched an invasion of Iran over border disputes and a desire to gain control of oil-rich areas in Iran's territory. The conflict lasted for eight years and ended in a stalemate. During the war, Iraq used chemical weapons and violence against Iraqi Kurds and Marsh Arabs, who were accused of colluding with Iran. While Iran did not support the multi-national coalition against Iraq's invasion of Kuwait in 1991, it housed many Shia political organizations opposing Saddam's rule. The fall of Saddam Hussein in 2003 and the eventual rise to power by pro-Iranian Shia factions (i.e. Islamic Dawa Party and Islamic Supreme Council of Iraq) led to the normalization of relations between the two countries. Since 2003, Iraq has allowed Shia Muslims from Iran to make the pilgrimage to holy Shia sites in Iraq. In March 2008, Iranian president Mahmoud Ahmadinejad became the first Iranian president to visit Iraq since Iran's 1979 Islamic revolution. Former Iraqi prime minister Nouri al-Maliki has made several state visits to Iran since 2006 and expressed sympathy with Iran over its nuclear energy program. Iran has since become Iraq's largest trading partner. Iran and Iraq are very close allies supporting each other against the Islamic State. The relationship between the two countries is strong in part due to the fact that both governments operate on a Shi'ite system of governance. Increasing influence of Tehran in Iraqi politics has led to civilians protesting the foreign involvement and presence of Iran-backed militias harassing and attacking citizens. Iran has an embassy