After the radical Islamic Republic of Iran was established in 1979, its relations with Iraq grew increasingly strained. Iran's new Shiite rulers disliked the secular foundations of Iraq's Baath regime. Ayatollah Ruhollah Khomeini, the spiritual leader of Iran's revolution, made it clear that he would like to see Saddam's government replaced by an Islamic republic. When several militant Shiite groups in Iraq began committing terrorist acts, Saddam believed that Khomeini was responsible.
Although Iraq and Iran had signed a border treaty in 1975, both countries were unhappy with its terms. Following several military exchanges, Saddam announced on September 17, 1980, that he was voiding the treaty because of Iranian violations. On September 22, Iraqi troops mounted a surprise invasion of Iran, and the Iraqi air force bombed Iranian military bases.
Although Saddam's real motivations for undertaking this war remain somewhat unclear, he apparently was determined to make Iraq the dominant power in the region around the Persian Gulf. Perhaps he wanted to occupy Iran's oil-rich province of Khuzistan, the home to many Sunni Arabs. There were also indications that Saddam hoped to overthrow Khomeini's revolutionary government, which at that time appeared to be chaotic and weak. On September 28, the United Nations Security Council passed a resolution calling for a cease-fire and a peaceful resolution to the border dispute, but neither side appeared interested.
For the first few months of the war, Iraq appeared to be winning. By mid-November, Iraqi troops had occupied Khorram-shahr and besieged Abadan. However, the religiously inspired Iranian forces managed to stop the Iraqi advance. In September, 1981, the Iranians began a series of successful counter-offensives. The war soon became a stalemate.
On June 9,1982, Iraq announced that it was ready for a truce, but the Iranian government in Teheran responded that peace was impossible so long as Saddam Hussein remained in power. In July, 1982, Iran began invading Iraqi territory, with the intention of capturing Basra province, and the two opposing forces engaged in the largest infantry battle since World War II.
Between March, 1983, and April, 1984, the Iranians threatened the city of Basra, while a united Kurdish-Iranian offensive threatened a large area in the northeastern provinces. Saddam responded by ordering that chemical weapons be used against Kurdish villages. A stalemate was followed by another Iranian offensive.
By January, 1987, the Iranians got to within seven miles of Basra but failed to take the city. On July 20, the U. N. Security Council passed Resolution 587. It called for a cease-fire and a withdrawal of all military forces.
Fearing an Iranian victory, the United States increased its support for Iraq, even after an Iraqi missile struck the USS Stark, killing thirty-seven American sailors. The United States changed the flags on eleven Kuwaiti tankers and escorted them through the Persian Gulf. In October, U. S. forces began attacking Iranian ships and oil platforms.
By early 1988 Iraq had an advantage over Iran in manpower and money. It demoralized the Iranians by striking Teheran with a medium-range missile. Between April 16 and 18, Iraq retook the Fao peninsula, again using chemical weapons. U. S. warships destroyed an Iranian frigate, and on July 3 a U. S. cruiser shot down an Iranian civilian airliner carrying 290 people which it mistook for a warplane. By July, Iraqi forces were on the offensive in Iran, and Iranian leaders persuaded Khomeini that Iran must accept a truce to save the Islamic revolution. The two countries agreed to peace terms on August 20,1988, but the war continued. Fighting finally ended in 1990, after Iraq agreed to respect the 1975 treaty, and the two sides exchanged prisoners of war. Although about a million people died during the war, neither side had accomplished much. Iraq emerged as the most powerful country of the region, as it had wanted. However, it had an accumulated war debt of about US$80 billion—about half which it owed to Kuwait and Saudi Arabia.