A Fiercer Fight to Come in Mosul

Four months into the campaign to reclaim Mosul from the Islamic State, Iraqi troops have taken the city's eastern portion. But the fight for the western part is only just beginning. Western Mosul is the core of the Islamic State's resistance. An estimated 2,000 Islamic State fighters are still in the area, along with more than 750,000 civilians, some of whom are suspected sympathizers of the extremist group. On top of that, the dense, cramped quarters of western Mosul's Old City will present an urban warfare environment even more challenging than that of the eastern part of the city, which took three months to clear. The fight for western Mosul is a critical turning point in the operation to retake the city, and it promises to be the most grueling battle yet.

North of Mosul, Iraqi counterterrorism forces, accompanied by the army's 16th Division, are driving toward the village of Badush in an effort to isolate western Mosul from the surrounding areas still under Islamic State control. The coalition announced Feb. 15 that the 16th Division would be in charge of keeping Islamic State militants from re-entering Mosul, where the extremist group still holds a significant chunk of territory. At the same time, reports suggest that Shiite Popular Mobilization Forces have joined Iraqi elements west of Mosul — though they have not entered the city — to distract the Islamic State from the coalition advances to the north and south. Shiite militia leaders at the Syrian border also announced that they had closed the gap near Tal Afar, limiting the Islamic State's ability to flee into Syrian territory.

In the city itself, Iraqi special operations forces have established sniper positions along the Tigris River and set up a strong defensive front on its eastern bank to prevent Islamic State militants from re-entering eastern Mosul. Coalition forces have also brought in equipment to eventually conduct bridging operations, launching an attack against Islamic State fighters across the river. Though the coalition had success with this technique while advancing up the Tigris River from the south, launching an assault onto the densely populated west bank from across the river will be a significantly more complex endeavor. Any such attempt will have to be tightly coordinated, synchronizing the movement of the assault force with withering fire support. Given how exposed troops attempting to cross the river would be, the slightest strategic misstep could doom the effort. 

Because of the risks associated with an opposed river crossing, Iraqi forces will likely employ a bridging operation as part of a larger attack across multiple fronts. The Islamic State has a natural advantage over the coalition in the urban environment — urban terrain favors the defender. Additionally, the group spent months shoring up its position in the city before the campaign began. It has worked diligently to even the playing field with the better-equipped and numerically superior Iraqi coalition, building elaborate tunnel networks beneath Mosul and digging defensive lines on the city's southwestern edge. Its main objectives in the fight are to inflict as many casualties as possible and to erode its opponents' morale over time. Even so, Iraqi forces have the distinct advantage of vastly outnumbering the Islamic State in Mosul. By attacking on multiple fronts, the coalition can achieve a disproportionate effect against a smaller force. The militant group will have no choice but to overextend its remaining fighters, creating exploitable vulnerabilities. 

Barring a military disaster, coalition forces will manage to rid western Mosul of Islamic State forces. The question is not whether but when — and at what cost to Iraq's military, Mosul's civilians and the city's infrastructure. Tensions between the coalition and the local population, and among the Iraqi forces themselves, are already high; Iraqi and Kurdish news outlets have reported that Kurdish peshmerga fighters are torturing civilians in eastern Mosul. Stories of similar atrocities have circulated about members of the Shiite militias and Iraqi federal police.

Though some reports are more credible than others, they nonetheless speak to the challenges that await Mosul once coalition forces have ousted the Islamic State from the city. Discontent among Mosul's mostly Sunni population over harsh treatment from Baghdad and the predominantly Shiite Iraqi security forces — combined with competition among various ethnic and sectarian groups — enabled the Islamic State to overrun the city in 2014. It is still unclear whether Baghdad will be able to prevent a similar situation from developing after the fight against the Islamic State has concluded. When Western countries start pulling their support from Iraq in the wake of the extremist group's retreat, regional powers will likely step in to help ensure its stability. In the process, they will create a different kind of competition and discord in the country.

This article appeared originally at Stratfor.