In September 1980, Iraqi forces launched a full-scale invasion of neighboring Iran, beginning the Iran-Iraq War. Fueled by territorial, religious and political disputes between the two nations, the conflict ended in an effective stalemate and a cease-fire nearly eight years later, after more than half a million soldiers and civilians had been killed.

Tensions between Iran and Iraq began almost immediately after the establishment of the latter nation in 1921, in the aftermath of World War I. By the 1970s, one enduring source of conflict involved control of the Shatt al-Arab, the waterway formed by the confluence of the Tigris and Euphrates Rivers, the southern end of which forms the border between the two nations. Signed in 1975, the Algiers Agreement reduced Iraqi control over the waterway in exchange for Iran’s withdrawing support for a Kurdish insurgency in northern Iraq.

A turning point occurred with the Iranian Revolution of 1978-79, which toppled the pro-Western government of Shah Mohammad Reza Pallavi in favor of a fundamentalist regime led by Shi’ite Muslim cleric Ayatollah Ruhollah Khomeini. Saddam Hussein, who became president of Iraq and leader of the country’s Ba'ath Party in July 1979, counted on the support of his nation’s minority Sunni Muslim population, and feared an expansion of Iran’s revolution to Shi’ite-dominated Iraq. Saddam also sought to overturn the border agreements of 1975 and reassert control over both sides of the Shatt al-Arab, Iraq’s only access point to the Persian Gulf.

Mindful of Iran’s weakened military in the wake of its revolution, Saddam decided on a preemptive strike against Iran. On September 22, 1980, Iraqi forces launched air strikes on Iranian air bases, following up with a ground invasion of the oil-producing border region of Khuzestan. The invasion was initially successful, with Iraq capturing the city of Khorramshahr and making other territorial gains by November.

But the Iraqi advance soon stalled in the face of a stiff Iranian resistance, powered by the addition of revolutionary militia to the regular armed forces. In 1981, Iran launched a counteroffensive; by early 1982, they had regained virtually all of the lost territory. By the end of that year, with Iraqi forces withdrawn to pre-war border lines, Iraq attempted to seek peace. Under Khomeini’s leadership, Iran refused, insisting on continuing the conflict in an effort to topple Saddam’s regime. In July 1982, Iran invaded Iraqi territory in an unsuccessful attempt— the first of many—to gain control of the Iraqi port city of Basra.

With Iran now on the offensive, Iraqi defenses solidified, and the war settled into a virtual stalemate along a front running roughly along the border. Both sides launched air and missile attacks against cities, military sites and oil facilities and transports, prompting the United States and other Western powers to send warships to the Persian Gulf to regulate the output of oil to the global market.

While Iran enjoyed a large numerical advantage, Iraq had more sophisticated weaponry and a better-trained officer corps, thanks to direct support from Saudi Arabia, Kuwait, and other Arab states and tacit support from Western nations including the United States.

In the aftermath of the 1979-81 hostage crisis involving diplomats at the U.S. embassy at Tehran, Khomeini’s regime remained largely isolated from the international community; Iran’s only allies during the conflict were Syria and Libya. Iraq continued to seek peace, but drew outrage from the international community for its use of chemical weapons against Iranian troops as well as Kurdish civilians in Iraq, who were thought to be sympathetic to Iran.

In the spring of 1988, with Iran demoralized by its many failed offensives over the years, Iraq launched its own series of ground attacks. Iraqi battlefield gains convinced Iran’s clerical leaders they had little hope of decisive victory. That July, the two nations agreed to accept a United Nations-brokered ceasefire under Security Council Resolution 598; the war ended formally on August 20, 1988. Though total casualty figures in the Iran-Iraq War are uncertain, estimates range from 1 to 2 million, with the total number killed reaching an estimated 500,000, including tens of thousands of Kurds killed by Iraqi forces.

As nearly all Arab nations had supported Iraq during the war in order to contain Iran, Iraq emerged from the conflict with more power in the region than it had before, fueled by a strengthened military and the ruthless ambition of its leader. On August 2, 1990, Saddam ordered the invasion of Kuwait, beginning the first Persian Gulf War.

Iran–Iraq War. International Encyclopedia of the Social Sciences, edited by William A. Darity, Jr., 2nd ed., vol. 4, Macmillan Reference USA, 2008.

Iran-Iraq War. Encyclopedia Britannica.

“Iran-Iraq War: Eight Brutal Years.” New York Times, July 22, 1988.

Paul Johnson. Modern Times: The World from the Twenties to the Nineties (Revised Edition). (Harper Perennial, 1991)