300px-Iran-Iraq War Montage

Clockwise from above: Iranian soldiers wearing gas masks to counter Iraqi chemical weapons, happy Iranian soldiers after the liberation of Khorramshahr, Donald Rumsfeld and Saddam meeting in Baghdad to discuss American military aid to Iraq, Iranian oil platform burning after attack by American Navy in Operation Nimble Archer

The Iran–Iraq War, also known as the Imposed War and Holy Defense in Iran, and Saddām's Qādisiyyah in Iraq, was a war between the armed forces of Iraq and Iran lasting from September 1980 to August 1988.

The war began when Iraq invaded Iran, launching a simultaneous invasion by air and land into Iranian territory on 22 September 1980 following a long history of border disputes, and fears of Shia insurgency among Iraq's long-suppressed Shia majority influenced by the Iranian Revolution. Iraq was also aiming to replace Iran as the dominant Persian Gulf state. Although Iraq hoped to take advantage of revolutionary chaos in Iran and attacked without formal warning, they made only limited progress into Iran and within several months were repelled by the Iranians who regained virtually all lost territory by June, 1982. For the next six years, Iran was on the offensive. Despite calls for a ceasefire by the United Nations Security Council, hostilities continued until 20 August 1988. The last prisoners of war were exchanged in 2003.