The April 4 Sarin gas attack on Khan Sheikhoun, just one day after the U.S. administration changed its position vis-à-vis Syrian President Al-Assad, declaring that his removal from power was no longer a priority, raised questions regarding the underlying motive for the attack. Indeed, the initial Russian claim that the attack had been fabricated by opponents of the Syrian regime was based on its being so clearly against Syrian interests.
While it is now largely accepted that the Syrian regime carried out the attack, the motivation underlying it remains enigmatic, giving rise to conspiracy theories.
Iranian Website Specializing In Syrian War Reports Provides The Explanation: To Prevent Breakdown Of Iranian/Syrian Frontline
On April 7, 2017, WarReports, an Iranian research group dedicated to monitoring and covering Iran’s role in the war in Syria and Iraq, published a report on its Facebook page, explaining why the Syrian regime had carried out the gas attack. It claimed that the attack had been “in support of the Iranian-affiliated ground forces, Hizbullah, and the Syrian army, all of which were stationed several kilometers behind the frontline.” According to the report, in the past three weeks there had been 21 casualties from among the IRGC forces and the Fatimiyun Afghani Shi’ite militia located in Hama. The report included a map of the region, showing the retreat southward of the Iranian-backed forces from the Khan Sheikhoun region, a retreat that threatened to turn into a complete breakdown of the front. The attack, therefore, was intended to curb the rebel thrust in Khan Sheikhoun, thus preventing this breakdown.
The report further stated that hitting the civilian population in the rebel-held areas was a known tactic of the Syrian regime, intended to crush the fighting spirit of the forces and to stop their operations. This was the case in the August 2013 gas attack on Ghouta, Damascus, and the October 2015 cluster-bomb attack on the civilization population of eastern Aleppo.
It should be noted that in a recent White House intelligence briefing, officials gave the same rationale for the Syrian regime attack, without providing further details: “They were losing in a particularly important area. That’s what drove [the attack].”
Red areas: territory held by Iranian/Syrian-regime forces
Green areas: territory held by the Jabhat Fath Al-Sham (formerly JNS) armed rebels
Red circle: Khan Sheikhoun
Red arrows: distance from Khan Sheikhoun to the Iranian-backed forces
Black dotted line: opposition frontline prior to March 21 operations and Iranian forces retreat
Red dotted line: current opposition frontline following the Iranian forces retreat
 The website provided a link to the image of one of the IRGC members killed there. https://goo.gl/iunWwn