One attack in 1988 on the Kurdish town of Halabja killed over 6,000 civilians.
 UN Security Council Resolution 687, passed on 3 April 1991 after Iraq's defeat in the Gulf War, mandated the complete dismantlement of Iraq's WMD programs, including the CW program.
Chemical weapons attacks collectively resulted in over one million Iranian casualties by the end of the war.
However, the United States and others remained concerned that Iraq had reconstituted its WMD programs, including its chemical weapons program. However, the post-war survey of Iraq’s WMD activities (known as the Duelfer Report) found that Iraq’s chemical weapons program had been successfully dismantled, although evidence suggested that the Iraqi government had hoped to reconstitute the program in the future.This decision led to UNSCOM's withdrawal in December 1998, followed by Operation Desert Fox in which the United States and United Kingdom bombed a number of facilities thought to have been used in reviving Iraq's WMD programs. government's belief that Iraq had reconstituted its CW program. This was despite findings by the UN Monitoring, Verification, and Inspections Commission (UNMOVIC), the organization that replaced UNSCOM, that there was no evidence of Iraqi continuation or resumption of WMD programs.On 19 March 2003 a United States-led coalition invaded Iraq and overthrew Saddam Hussein.  In April 2003 the United States tasked the Iraq Survey Group (ISG), headed by former UN inspector David Kay, with locating suspected WMD stockpiles and equipment. Bombardments began with tear gas and expanded to include mustard gas attacks during the 1983 Val Fajr II campaign near Haj Umran. Over the course of the war, Iraq continued to use mustard gas, tear gas, and eventually the nerve agent tabun.