By Isabel Nassief and Jennifer Cafarella

Secretary of Defense Chuck Hagel told reporters that U.S. airstrikes “have stalled ISIL's momentum” after two weeks of bombarding ISIS positions in Northern Iraq. The Islamic State of Iraq and al-Sham has not stalled under U.S. pressure. Rather, since the fall of Mosul and despite U.S. airstrikes, the insurgent army has continued a successful and spectacular offensive in Syria. Their gains nearly equal in scale the seizure of northern Iraq in June. The insurgent army’s latest triumph is the capture of Assad’s Tabqa air base in Eastern Syria.

ISIS is one armed force fighting on multiple fronts in two theaters of operation, Iraq and Syria, across a border that the group does not recognize. It aims to establish and consolidate a cross-border Caliphate and has sought to fuse its lines of communication across the border region, while also seizing control of populated urban areas in both countries. ISIS has sought to expel armed forces of both states from positions within ISIS’s desired “borders” in order to preserve the Caliphate’s territorial integrity.

ISIS operations in Syria have centered on five main objectives: control of the Euphrates River Valley; seizure of critical oil infrastructure; freedom of maneuver through Kurdish areas of Syria; expulsion of remaining regime forces from bases in Eastern Syria; and seizure of critical supply lines along the Turkish border. ISIS thereby seeks to merge its Iraq and Syria fronts by consolidating lines of communication between the two. ISIS has continued to pursue these objectives in Syria despite U.S. airstrikes in Northern Iraq and the Syrian regime’s sustained air strikes in North-Eastern Syria. ISIS’s campaign has proceeded in Syria along four main fronts: the Euphrates River Valley in Deir ez-Zour province; Hasaka province; North-Western Aleppo province; and the Syrian regime airbase in Raqqa province.

ISIS needs to control the Euphrates in Syria’s Deir ez-Zour province in order to link its de facto capital in Raqqa to its gains in Iraq’s Anbar province. After Iraq’s upper Euphrates towns fell swiftly in June, ISIS secured the surrender of local rebel and tribal groups in Deir ez-Zour, allowing ISIS forces to establish territorial control throughout July without expending resources in a military offensive. The She’tat tribe in southeastern Deir ez-Zour province initiated a small-scale tribal rebellion, threatening ISIS’s hold on the province. ISIS swiftly moved to regain control, even as U.S. airstrikes commenced. ISIS is not stopping at controlling the tribal areas, but rather seeks to remove the regime from its remaining strongholds in the province, as indicated by an SVBIED against the regime base within the province on August 15.