Background
In 1979 there was a revolution in Iran. The religious leader Ayatollah Ruhollah Khomeini took control of the country. Khomeini, along with most of the people of Iran, belonged to the Shi?ah branch of Islam. Iraq also had a majority of Shi?ite Muslims in its population. However, Iraq's rulers belonged to Islam's other major branch, the Sunnah. President Saddam Hussein of Iraq was afraid that Iran might encourage Iraq's Shi?ites to rebel against him. Saddam also resented the Iranians for supporting the Kurds, a minority group, as they fought for independence from Iraq in the 1960s and 1970s.
Saddam Hussein used a long-standing border dispute with Iran as an excuse to begin a war. He claimed that Iraq should control both banks of the Shatt Al-?Arab, a river that historically formed part of the boundary between Iran and Iraq. Saddam also wanted to gain control of Khuzestan, an oil-producing area in southwestern Iran where many Arabs lived. Arabs make up only a small part of Iran's population, but they are the largest ethnic group in Iraq.
Events of the war
Iraq invaded Iran by surprise on September 22, 1980. Saddam Hussein believed that Iran's religious revolution had weakened its military. It was true that many of Iran's best military leaders had been killed during the revolution. After winning a few early victories, however, Saddam found that Iran did not give up as he had expected. The Iranian military stopped and eventually drove back the invaders.
By mid-1982 Iran had won back almost all the land that Iraq had captured in the invasion. Then Iranian forces pushed into Iraq. For the next five years the two sides were evenly matched. Both countries suffered heavy losses in lives and property without winning important military victories.
Iran tried repeatedly between 1982 and 1987 to take over Basra, Iraq's most important port for exporting oil. Iraq successfully defended the city and fought back, with help from other Arab countries, the Soviet Union, France, Great Britain, and the United States. Iran and Iraq bombed each other's cities and oil fields. They also attacked each other's tankers, which were used for shipping oil, in the Persian Gulf.
Neither country followed the usual rules of war. Iraq used chemical weapons against Iranian forces and against Iraqi Kurds who Iraq claimed were helping the Iranians. No country had used such weapons on a large scale since World War I. Iran sent young village boys through minefields ahead of its troops. Many of the boys set off the land mines, giving up their lives so that the troops behind would have a clearer path.
In 1987 Iraq started to gain the upper hand in the fighting. By mid-1988 Iraqi forces had moved deep into Iran. Realizing that it could not win the war, Iran accepted a United Nations resolution that ended the fighting. Iraq had already agreed to the resolution, which came into force on August 20, 1988. At least 1 million people had died in the war.
Peace talks continued until 1990. Eventually Iran and Iraq agreed to share control of the Shatt Al-?Arab river. The last Iraqi troops left Iran in 1991. The last prisoners of war were not exchanged until 2003.