The United States put the blame for the attack on the Syrian government and its patrons, Russia and Iran, and suggested that the salvo was a war crime. While the attack was among the deadliest uses of chemical weapons in Syria in years, it was far from an isolated case.

During the war, the Assad government has been accused of regularly using chlorine gas, which is less deadly than the agent used on Tuesday and is legal in its commercial form. According to the Violations Documentation Center, an antigovernment watchdog, more than 1,100 Syrians have been killed in chemical weapons and gas attacks.

There are also reports that the Islamic State, also known as ISIS, has used mustard agent in northern Syria.

Siege Tactics and Starvation