The impact of a major U.S.-Iran confrontation would be so large it is difficult to conceptualize, both in Syria, and in the region itself. Even if an all out war between the U.S. and Iran is avoided, the risk of instability and conflict in areas where Iranian-backed groups are in close proximity to the U.S. and its allies is extreme. This would certainly include Deir-ez-Zor and Abukamal in northeastern Syria, where Iranian-backed groups are within kilometers of U.S. military forces, and southern Syria, where Iranian-backed groups and Hezbollah are located in the vicinity of the Israeli border. Moreover, both the Syrian and Iraqi economies and military establishments are closely linked to Iran, whilst Lebanon risks being drawn into open conflict with Israel due to Hezbollah’s role in the Lebanese government. The latter would necessarily have an impact in Syria given the number of Syrian refugees in Lebanon, and the fact that much of the Syria response is based in Beirut. Conflict between the U.S. and Iran is by no means unavoidable, cooler heads may yet prevail, and indeed, U.S. President Trump appears to be opposed to U.S. military intervention as a general policy. However, a quote attributed to Barbara Tuchman (the author of The Guns of August, the seminal history of the start of WWI) comes to mind: “War is the unfolding of miscalculations.”