U.S. President Donald Trump’s recent decision to keep a residual force of at least 400 troops in Syria prevents the immediate takeover of valuable natural resources and infrastructure in Eastern Syria by Iran, Assad, and Russia. These actors nonetheless still have options that could lead to the defeat or expulsion of U.S. forces. The residual U.S. forces will operate at Al-Tanf on the Syrian-Jordanian Border as well as in Northern and Eastern Syria across the Euphrates River.
The garrison at Al-Tanf is relatively defensible with secure supply lines to Jordan as well as a limited tactical requirement to defend the base and a surrounding fifty-five kilometer exclusion zone, which includes the Rukban IDP Camp. The U.S. is significantly more vulnerable east of the Euphrates River. Iran, Assad, and Russia are building up forces west of the Euphrates River and using outreach to local tribes to gain footholds on its eastern bank. Even a limited drawdown by the U.S. will create security gaps east of the Euphrates River that could be exploited by Iran, Assad, and Russia.