S1, E2: The Iran–Iraq War was an armed conflict between the Islamic Republic and the Baathist Republic of Iraq lasting eight years making it the 20th century's longest conventional war. The Iran–Iraq War began when Iraq invaded Iran via air and land on September 22, 1980. It followed a long history of border disputes, and was motivated by fears that the Iranian Revolution would inspire insurgency among Iraq's long-suppressed Shia majority.