Chemical weapons watchdog concludes Islamic State used mustard gas in 2015 attack in Syria

An investigation carried out by the Organisation for the Prohibition of Chemical Weapons (OPCW) has concluded that there are ‘reasonable grounds’ to believe that Islamic State (IS) deployed sulfur mustard in attacks that took place on 1 September 2015 in Syria.

According to the findings of the investigation, which was carried out by the OPCW’s investigation and identification team (IIT) between January 2023 and February 2024, the chemical agent was delivered using one or more artillery pieces from areas under IS control. All remnants and munitions observed at several sites across the town of Marea, Syria, were conventional 122mm artillery projectiles modified to disperse a liquid payload, the report stated.