Prior to September 2013 Syria was one of a handful of states which had not ratified the Chemical Weapons Convention , and had not publicly admitted to possessing chemical weapons , although Western intelligence services believed it to hold a massive stockpile . In September 2013 , French intelligence put the Syrian stockpile at 1,000 tonnes , including Yperite , VX and " several hundred tonnes of sarin " . After international condemnation of the August 2013 Ghouta chemical attack , for which Western states held the Syrian government responsible ( whilst Syria and Russia held the Syrian rebels of the Syrian civil war responsible ) , in September 2013 Syria joined the Convention ( formally acceding on 14 October ) , as part of its agreement to the destruction of its chemical weapons under the supervision of the Organisation for the Prohibition of Chemical Weapons . In October 2013 , the OPCW found a total of 1,300 tons of chemical weapons
Ghouta chemical attack
Ghouta chemical attack
Syria and weapons of mass destruction