The exact number killed is not known, but ran into the thousands as townspeople choked on a mixture of mustard gas and nerve agents.
BBC: Iraqi Kurds mark 25 years since Halabja gas attack
2.
Military and armaments experts say the government started to stockpile chemical weapons in the late 1970's, and now possesses or is capable of producing VS agents, sarin and mustard gas.
WSJ: Syria Chemical Report Spurs Probes, Theories
3.
This, he believes, will make it possible to work out which country, even which factory, supplied the original chemicals for the mustard gas - it will not be possible to trace the source of the nerve agents.