The forces aligned against the Islamic State are fast closing in on the Iraq-Syria border, seizing control of critical territory held by the Islamic State as they go. With the successful capture of Deir el-Zour, Syrian forces loyal to the government in Damascus have removed the Islamic State from its last significant urban stronghold. Elsewhere in the province, the U.S.-backed Syrian Democratic Forces (SDF) have continued driving the Islamic State back from a number of villages and oil and natural gas fields. On the Iraq side of the border, the Iraqi Army, supported by Iran-backed Shiite militias, has cleared large areas of Anbar province from Islamic State control, reaching the Syrian border on the Damascus-Baghdad highway.

The goal for all three broad factions is not just to defeat the Islamic State but to gain possession of the territory left behind. Syrian loyalist forces are attempting to reach the Iraq-Syria border before the U.S.-backed SDF to establish a land corridor between Syria, Iraq and Iran. The land corridor, which would run through the Damascus-Baghdad highway, would shore up Iran's supply routes to the Syrian government and to Hezbollah in Lebanon. For now, Iran can supply its allies in Syria and Lebanon only by air and maritime routes. But air traffic is inadequate for large goods and shipping is vulnerable to Israeli interception.

Though there is the possibility that U.S.-backed SDF fighters may make a lightening advance and reach al-Bukamal first, loyalist forces are likely to arrive first and to consolidate their positions along the Iraq-Syria border. Supported by Hezbollah and other Iran-backed Shiite militias, the Syrian loyalist forces are about 45 kilometers (28 miles) from al-Bukamal. In addition, Iraqi Shiite militias could facilitate the Syrian loyalist forces' advance by pressuring the Islamic State from the Iraqi border (possibly crossing the border into Syria).