After a short pause in the intense fighting with rebels in Syria's eastern Deir el-Zour province, the Islamic State is once again escalating its offensive operations in Syria, this time across a broader front. Although distracted by the major thrust into Iraq and its commitments there, the group is again challenging the rebels in Deir el-Zour, the largest city along the Euphrates River Valley in eastern Syria. It is attempting to take territory from the Kurds in an effort to re-establish a foothold in western Syria, a move that would bring Islamic State fighters into greater contact with loyalist and regime forces.
The Islamic State has apparently decided that continuing its offensive momentum by pushing hard in Syria, while holding recent gains in Iraq, is important enough to risk the possibility of overreach. As long as the Islamic State continues to make important gains in the region, it is likely to benefit from defecting fighters and jihadists from other organizations and to capitalize on the seizure of equipment and resources. The strategy is fraught with risk, however, as the Islamic State continues to fight enemies in Syria and Iraq.
Overall, the Islamic State is attempting to carve out and consolidate territory, predominantly in a region bounded by the Tigris River Valley in Iraq and the Euphrates River Valley as it runs through Iraq and northeastern Syria. This is part of a strategic effort to secure an Islamic state, thereby taking advantage of the resources gained by holding such territory. Most of the population and resources in this region are centered on the river valleys, with broad swaths of desert in between, oil fields being one notable exception. While the current Islamic State offensive in Iraq has stalled, the boon in materiel and reputation has allowed for renewed efforts in Syria. Islamic State forces remaining in Iraq continue to fight against security forces, hampering counteroffensives in the north.
Increased Risk, Increased Payoff
The risks notwithstanding, the Islamic State has already made significant progress in Syria over the past week, particularly in Deir el-Zour. A number of local tribes, greatly influenced by the events in Iraq, pledged allegiance to the Islamic State in the aftermath of the organization's successes in Iraq. The newfound support from local tribes, alongside a few units of Jabhat al-Nusra that switched sides, upended the balance of power in the vast eastern Syrian province, turning the tide in favor of the Islamic State. After a few days of pitched fighting in which some towns changed hands multiple times, rebels and jihadists from Jabhat al-Nusra and the Islamic Front made a strategic retreat from most of the province. The Islamic State was thus able to claim a significant amount of territory and key resources — such as the al-Omar oil field, the largest in Syria — without a fight.
The Islamic State's advance did not end there. Using vehicles and equipment captured in Iraq, Islamic State forces in northern Syria advanced against Kurdish forces and seized several villages, killing dozens of Kurdish People's Protection Unit fighters. Attacking west from Tal Abyad and east from Jarablous, the Islamic State now threatens a large Kurdish-controlled pocket of territory centered on the important border crossing of Ayn al-Arab.
With Islamic State forces encroaching on Deir el-Zour after displacing a large number of rebel forces, Islamic State jihadists are already clashing with loyalist forces in the province's main city. Furthermore, recent advances on the Iraqi side of the border threaten to permanently close the al-Tanf border crossing, which is critical for the regime's logistical supply of raw resources, equipment and fighters from Iraq and Iran. The Islamic State is also set to increase its operations against the isolated loyalist 17th division in Raqqa, while seeking to establish a foothold in other regime-controlled areas such as Homs and Rif Damascus.
In the short term, recent Islamic State advances have particularly hurt the other rebel groups in Syria, denying them key sources of revenue and cutting them off from support in Iraq. The Islamic State is also threatening to make a comeback in Aleppo, having been ousted from the northern city earlier this year by a coalition of moderate rebel forces. This generates the potential for conflict not only with these forces but also with regime forces in and around Aleppo. If that were to occur, increased weapons shipments from the United States to the rebels may well end up being used against both the regime and the Islamic State.
In the longer term, however, the Islamic State is becoming a deadly threat to all factions in the Syrian conflict. For now the Islamic State can afford to push its gains in Syria as it capitalizes on its success in Iraq, but the risk remains that the group may very well end up overstretched on two fronts, facing counterattacks from a mixture of local, regional and international actors that view it as a growing menace.