Iraq invades Iran, sparking the nearly eight year Iran–Iraq War.

The Iraqi invasion of Iran began on 22 September 1980, sparking the Iran–Iraq War, and lasted until 5 December 1980. Ba'athist Iraq believed that Iran would not respond effectively due to internal socio-political turmoil caused by the country's Islamic Revolution one year earlier. However, Iraqi troops faced fierce Iranian resistance, which stalled their advance into western Iran. In two months, the invasion came to a halt after Iraq occupied more than 25,900 square kilometres (10,000 sq mi) of Iranian territory.

The Iran–Iraq War was an armed conflict between Iran and Iraq that lasted from September 1980 to August 1988. Active hostilities began with the Iraqi invasion of Iran and lasted for nearly eight years, until the acceptance of United Nations Security Council Resolution 598 by both sides. Iraq's primary rationale for the attack against Iran cited the need to prevent Ruhollah Khomeini—who had spearheaded the Iranian revolution in 1979—from exporting the new Iranian ideology to Iraq. There were also fears among the Iraqi leadership of Saddam Hussein that Iran, a theocratic state with a population predominantly composed of Shia Muslims, would exploit sectarian tensions in Iraq by rallying Iraq's Shia majority against the Baʽathist government, which was officially secular but dominated by Sunni Muslims. Iraq also wished to replace Iran as the power player in the Persian Gulf, which was not seen as an achievable objective prior to the Islamic Revolution because of Pahlavi Iran's economic and military superiority as well as its close relationships with the United States and Israel.