The Iran–Iraq War began on 22 September 1980, when Iraq invaded Iran, and it ended on 20 August 1988, when Iran accepted the UN-brokered ceasefire. Iraq wanted to replace Iran as the dominant Persian Gulf state, and was worried that the 1979 Iranian Revolution would lead Iraq’s Shi’ite majority to rebel against the Ba’athist government. The war also followed a long history of border disputes, and Iraq planned to annex the oil-rich Khuzestan Province and the east bank of the Arvand Rud (Shatt al-Arab).

Although Iraq hoped to take advantage of Iran’s post-revolutionary chaos, it made limited progress and was quickly repelled; Iran regained virtually all lost territory by June 1982. For the next six years, Iran was on the offensive[55] until near the end of the war.[50] There were a number of proxy forces—most notably the People’s Mujahedin of Iran siding with Iraq and the Iraqi Kurdish militias of the KDP and PUK siding with Iran. The United States, Britain, the Soviet UnionFrance, and most Arab countries provided political and logistic support for Iraq, while Iran was largely isolated.

After eight years, war-weariness, economic problems, decreased morale, repeated Iranian military failures, recent Iraqi successes, Iraqi use of weapons of mass destruction, lack of international sympathy, and increased U.S.–Iran military tension all led to a ceasefire brokered by the United Nations.

The conflict has been compared to World War I in terms of the tactics used, including large-scale trench warfare with barbed wire stretched across fortified defensive lines, manned machine gun posts, bayonet charges, Iranian human wave attacks, extensive use of chemical weapons by Iraq, and, later, deliberate attacks on civilian targets. A special feature of the war can be seen in the Iranian cult of the martyr which had been developed in the years before the revolution. The discourses on martyrdom formulated in the Iranian Shiite context lead to the tactics of “human wave attacks” and thus had a lasting impact on the dynamics of the war.[56]

An estimated 500,000 Iraqi and Iranian soldiers died, in addition to a smaller number of civilians. The end of the war resulted in neither reparations nor border changes.