Chemical attacks in Syria reminiscent of Saddam's attack
It is believed that Iraqi forces used multiple chemical agents during the attack, including (mustard gas) and nerve agents. ... Prior to the Halabja incident there were at least 21 documented smaller-scale chemical attacks against Iraqi Kurds, none of which prompted any serious response from the international community.
Halabja chemical attack - Wikipedia
https://en.wikipedia.org/wiki/Halabja_chemical_attack