On April 4, 2017, Syrian air raids pummeled the small rebel-held town of Khan Sheikhoun in the northern province of Idlib.
As news of the attack spread, it quickly became apparent that something other than conventional weapons had been used.
Residents told Al Jazeera they saw people choking and foaming at the mouth, “suffocating while their lungs collapsed”.
More than 80 people, including many women and children, died when nerve agent sarin or a sarin-like substance was dropped onto Khan Sheikhoun. Hundreds more were wounded, in one of the worst chemical attacks since sarin gas killed hundreds of civilians in Ghouta, near the capital, Damascus, in August 2013.
Syria’s government has denied involvement and claims it no longer possesses chemical weapons after a 2013 agreement under which it pledged to hand over thousands of tonnes of deadly chemical agents following US threats of a unilateral attack.
But in October 2017, the Joint Investigative Mechanism, a group tasked by the UN Security Council and the Organisation for the Prohibition of Chemical Weapons (OPCW) to investigate chemical weapons attacks, confirmed that the chemical attack on Khan Sheikhoun did happen, and that the Syrian government was responsible for the killing of civilians.
On the one-year anniversary of the Khan Sheikhoun attack, Al Jazeera’s Faisal Edroos spoke with Hamish de Bretton-Gordon, a chemical weapons adviser to NGOs working in Syria and