The Iran-Iraq War (1980-1988)

In March 1975, Shah Mohammad Reza Pahlavi of Iran and Iraqi Vice President Saddam Hussein signed the Algiers Agreement, settling a long-running border dispute over the Shatt al-Arab waterway. Under the agreement, Iraq ceded to Iran the eastern bank of the waterway in exchange for Iran ceasing support for Kurdish insurgents in northern Iraq. The agreement quieted the dispute for five years, until the 1979 Iranian Revolution removed the Shah and reshaped regional power dynamics.

In February 1979, the Iranian Revolution overthrew Shah Mohammad Reza Pahlavi, and Ayatollah Ruhollah Khomeini returned from exile to establish the Islamic Republic of Iran. Khomeini openly called on Iraqis to overthrow the secular Ba'athist government in Baghdad, alarming Iraq's Sunni leadership, who feared that Iran's Shia-majority population would be similarly inspired. Iraq's ruling Ba'ath Party responded in July 1979 with overtures of friendship; Khomeini's rejection, combined with Iranian support for Iraq's Shia opposition groups, deepened the crisis.

In April 1980, the Islamic Dawa Party, an Iraqi Shia group with ties to Iran, attempted to assassinate Iraq's deputy prime minister Tariq Aziz. The attempt failed but killed several students at a university rally. Iraq responded by executing Grand Ayatollah Muhammad Baqir al-Sadr, the highest-ranking Shia cleric in Iraq, along with his sister Bint al-Huda, and declared membership in the Dawa Party a capital offense. The incident became part of Iraq's public justification for war.

On 22 September 1980, Iraq launched a full-scale invasion of Iran with coordinated air strikes on ten Iranian airfields, including Mehrabad Airport in Tehran, and a three-pronged ground offensive along a 644 km (400 mi) front. Saddam Hussein aimed to seize the oil-rich Khuzestan province, the eastern bank of the Shatt al-Arab, and either topple the Islamic Republic or compel it to stop exporting revolutionary ideology. The Iraqi Air Force failed to destroy Iran's air force, which had sheltered its combat aircraft in hardened bunkers, and Iran's retaliatory strikes disrupted Iraqi air operations within days.

Iraqi forces besieged the strategic southern oil port of Abadan and captured the city of Khorramshahr in late October 1980 after fierce fighting that included the first known Iraqi use of chemical weapons against Iranian troops near Susangerd. The capture of Khorramshahr became a rallying point for Iran. The city was later described by Iraqi officers as "the city of blood" after the heavy casualties. By December 1980, the Iraqi advance had stalled across all fronts, hampered by extended supply lines, internal Iraqi political divisions, and stiffening Iranian resistance.

In April 1982, Iran launched major counteroffensives in Khuzestan. In Operation Beit ol-Moqaddas, Iranian forces retook Khorramshahr on 24 May 1982, capturing more than 19,000 Iraqi prisoners of war. The victory ended Iraqi occupation of Iranian territory. Iranian leaders, however, refused to accept a ceasefire and instead chose to carry the war into Iraq, aiming to topple Saddam Hussein. This decision prolonged the conflict by six years.

Beginning in 1983, Iraq escalated its use of chemical weapons — including mustard gas and the nerve agent tabun — against Iranian troops along the front lines. Chemical attacks were also directed at Iranian civilians, including the 1988 attack on the Kurdish town of Halabja in northern Iraq, in which approximately 5,000 Kurdish civilians were killed and thousands more injured. The international community condemned the attacks but took limited action. The United States, France, and the Soviet Union, all of which had intelligence on the chemical weapons use, continued to support Iraq diplomatically and materially.

Beginning in 1984, the conflict spread to the Persian Gulf shipping lanes. Iran attacked oil tankers serving Iraq's Persian Gulf allies, particularly Kuwait and Saudi Arabia, while Iraq attacked tankers serving Iran. To protect Gulf shipping, the United States launched Operation Earnest Will in 1987 and reflagged Kuwaiti tankers under the US flag. On 17 May 1987, the USS Stark, a US Navy frigate operating in the Gulf, was struck by two Iraqi Exocet missiles, killing 37 US sailors. Iraq apologized and paid compensation, and the incident did not lead to direct US military retaliation.

On 20 July 1987, the UN Security Council unanimously passed Resolution 598, calling for a ceasefire, the withdrawal of forces to international borders, and the appointment of a UN peacekeeping force. The resolution also mandated an investigation into responsibility for the war. Iran initially welcomed the resolution in principle but later rejected it, demanding that Iraq first admit responsibility and pay war reparations. The stalemate continued for another year.

On 20 July 1988, Iran formally accepted UN Security Council Resolution 598. Ayatollah Khomeini, in a public address, likened the decision to drinking "a cup of poison." His decision came after a series of military setbacks and the 3 July 1988 downing of Iran Air Flight 655 by the USS Vincennes, which killed all 290 people aboard. Combined with the resumed Iraqi chemical weapons campaign, declining morale, and economic exhaustion, these events convinced Iran's leadership that the war could not be won by further military action.

Between 22 and 26 July 1988, Iraq's forces together with the Iranian exile group Mujahedin-e Khalq launched Operation Mersad into western Iran, advancing toward Khorramabad before being stopped by Iranian defenses. The failure of Mersad, coming just two days after Iran's acceptance of Resolution 598, helped consolidate the Iranian public's support for ending the war. The ceasefire took effect on 20 August 1988 after final notifications between the parties. The war ended without significant changes in borders, regime change, or war reparations, leaving both sides to claim victory.

In the months following the ceasefire, Iraq conducted the Anfal campaign against its own Kurdish population in northern Iraq, which killed an estimated 50,000 to 100,000 Kurds and culminated in the Halabja chemical attack of 16 March 1988. The war itself is estimated to have caused between 500,000 and 1 million deaths on both sides, with several hundred thousand wounded, and more than 1 trillion USD in economic damage. The unresolved trauma of the war shaped both states' subsequent behavior: Saddam's regime, weakened economically, invaded Kuwait in 1990 partly to recover lost revenues; Iran, with a generation of veterans and martyrs, strengthened the role of the Islamic Revolutionary Guard Corps in regional politics. The war's legacy continues to define Iran's relations with the United States, Israel, and the Arab world.