An estimated 5000 people were killed when up to 20 aircraft dropped the chemicals on the town on March 16, 1988. Many people in Halabja, which is close to the Iranian border, still suffer physically from the effects of the nerve and mustard gas."
Hussein's cousin Ali Hassan Abd al-Majid al-Tikriti, who was known as Chemical Ali, led the attack. He was hanged in 2010.
Blame was initially attributed to Iran but it later emerged that the attack had been ordered as part of Hussein's genocidal campaign against the Kurds towards the end of the Iraq-Iran war. A Chemical Weapons Convention was introduced in 1993 and 188 countries have since ratified the treaty which introduced a verifiable ban on an entire class of weapons of mass destruction. Syria has not signed up to the treaty.