The May 18 U.S. airstrike on pro-regime forces heading for Syria's southern al-Tanf border crossing marks a turning point in the war. The situation on the Iraq-Jordan-Syria frontier now poses the threat of direct confrontation between American and Syrian forces, and perhaps other actors as well.
Al-Tanf has been occupied by U.S. Special Forces and American-backed rebels since March 2016. Following last week's strike, Defense Secretary Jim Mattis quickly noted that the United States does not seek to increase its role in the war, though it would defend its troops if they are threatened. Meanwhile, Bashar al-Assad and his allies believe that Washington wants to establish a more permanent presence in eastern Syria in order to strengthen its local allies, put pressure on Damascus, and prevent the regime from returning to the Euphrates Valley.
This concern reflects the broader regional contest that the war has become, with the regime and its allies racing to establish an east-west "Shiite axis" from Iran to Lebanon and the United States seemingly looking to cement a north-south "Sunni axis" from the Gulf states and Jordan to Turkey. The situation in Syria's central and southern desert region (the Badia) will play an important role in shaping these dynamics.