Author's Update 9/12/18: The Syrian government, backed by Russian airpower and Iranian advisors, is preparing to undertake a major offensive designed to retake the province of Idlib from opposition forces. The newly appointed State Department Special Representative for Syria, Jim Jeffreys, claims that there is "Lots of evidence" that Syria is preparing to use chemical weapons, specifically chlorine gas, in support of the Idlib operation.

For its part, Russia claims to have specific intelligence that al Qaeda affiliates, working in conjunction with the White Helmet organization, is preparing to stage a chlorine gas attack designed to look like it was done by the Syrian government. The U.S. has warned that it would launch a major military strike against not only the Syrian government, but also Russian and Iranian targets in Syria, if chemical weapons were used in Idlib.