Iraqi chemical attacks against Iran

During the Iran–Iraq War (1980–1988), Iraq engaged in chemical warfare against Iran on multiple occasions, including more than 30 targeted attacks on Iranian civilians. Iran employed its own chemical warfare against Iraq on a few occasions during the war as well. Iraq's attacks represented the third deadliest use of chemical weapons in history, following the Holocaust and chemical warfare in World War I. Originally using mustard gas alone, in 1984 Iraq initiated the first verified combat use of nerve agents in history, beginning with tabun before moving to sarin.

The Iraqi chemical weapons program, which had been active since the 1970s, was aimed at regulated offensive use, as evidenced in the chemical attacks against Iraqi Kurds as part of the Anfal campaign in the late 1980s. The 1988 Halabja massacre in Iraqi Kurdistan, which killed at least 3,200 people, is considered of the worst attacks of the war. The Iraqis had also utilized chemical weapons against Iranian hospitals and medical centres. According to a 2002 article in the American newspaper The Star-Ledger, 20,000 Iranian soldiers and combat medics were killed on the spot by nerve agents. As of 2002, 5,000 of the 80,000 survivors continue to seek regular medical treatment, while 1,000 are hospital inpatients.

Operationally, Iraqi forces transitioned from artillery attacks, to low-altitude bombing, to high-altitude bombing. Nerve agents, with a lower persistency, were used on Iranian frontlines, and dissipated in time to be safely overrun by Iraqi forces. Mustard gas with its higher persistency was used for area denial and attack the rear of the battlefield. Iraq exploited the high temperatures that made it difficult for Iranian troops to wear protective suits and masks for extended periods.

Strategically, by the end of the war Iraqi chemical warfare had crippled Iranian morale. The threat that Iraqi Scud ballistic missiles, used with conventional warheads in the conflict's war of the cities, would carry chemical weapons caused fleeing of Iranian urban areas. Alongside 1988 ground and naval defeats, this is considered one of the reasons Iran accepted the United Nations-brokered ceasefire in August.

Though the use of chemical weapons in international armed conflict was banned under the Geneva Protocol, much of the international community remained indifferent to the attacks; Iraq's military campaign in Iran was supported by the United States and the Soviet Union, both of whom had sought to contain Iranian influence after the Islamic Revolution of 1979. Despite this, following the first nerve agent use in the 1984 Battle of the Marshes, the United States condemned Iraqi chemical attacks and began formal discussions at the Conference on Disarmament on what would become the 1993 Chemical Weapons Convention, comprehensively outlawing chemical weapon production, stockpiling, and use.