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.