After months of intensive preparations, the battle of Mosul is fast approaching. For much of the past year, Iraqi security forces have been streaming north and working to put the necessary logistics into place in anticipation of the offensive. Iraqi army Chief of Staff Gen. Othman al-Ghanmi announced on Oct. 13 that the preparations are complete, and Prime Minister Haider al-Abadi gave the order to launch the offensive early Oct. 17. A look at the situation around Mosul and the forces arrayed for battle can offer insight into what will come next.
Mosul is in northern Iraq on the Tigris River, which flows south through the city toward the town of Qayyarah, the site of a strategic air base. The city, surrounded by the Nineveh plains on the north and east and flanked by the Badush and Atshan mountain ranges to the west and northwest, is near several key roadways. Highway 1 runs through the desert north toward Mosul before proceeding west between the Badush and Atshan mountains. Highway 80 heads toward the city through the Nineveh plains from the south and east of the Tigris, and Highway 2 leads west from Arbil to Mosul before heading north to Dohuk.
Before the Islamic State seized the city in 2014, Mosul was Iraq's second-most populous city. Though Sunni Arabs make up the majority of the city's residents, Mosul has historically been home to sizable Kurdish, Turkmen, Assyrian, Armenian and Yazidi minorities as well. During the Islamic State's occupation, however, many of these minorities have been persecuted and driven out, and many Sunnis have fled the city, depleting its population from almost 2 million to approximately 750,000. Nonetheless, the effort to recapture Mosul will be the largest urban operation yet for the Iraqi forces getting ready to advance on it.
Currently, the city is tucked in a salient surrounded on three sides. Kurdish peshmerga fighters are positioned 15 to 20 kilometers (roughly 9 to 12 miles) to the north and east of Mosul, and they hold all of the mountainous ground that overlooks the Nineveh plains. The front lines, filled out with the Iraqi security forces who have been making their way up from the south, lie about 50 kilometers south across an arid and depopulated region. To the west is the last remaining link between Mosul and the rest of the territory the Islamic State controls. Since a Kurdish offensive in November 2015 took Sinjar and cut key roads heading west — including the main highway between Mosul and Raqqa — the Islamic State's supply lines to Mosul now rely on secondary roads through the mountains.
Altogether, approximately 40,000 to 50,000 fighters have amassed for the seizure of Mosul. Although four peshmerga divisions, supplemented by local allies, account for between 10,000 and 15,000 of the fighters, Iraqi security personnel — mainly from the 9th, 15th, 16th and 37th divisions — form the bulk of the coalition. Several ancillary units from the federal police and Sunni tribal militias will also be on hand to support the Iraqi troops, and thousands of Popular Mobilization Forces will round out the force in an auxiliary capacity. Numbers of available Islamic State fighters in Mosul, meanwhile, are difficult to gauge; estimates range from 2,000 to 7,000 fighters.
The Advance to Mosul
The battle will take place in phases, separated by considerable pauses. In the first phase, the advance to Mosul, the coalition will have two principal objectives: to tighten the perimeter around Mosul, placing the city under siege, and to start preparations for the breach of the city. The peshmerga, bolstered by numerous Iraqi army units and tribal forces, are arrayed east and north of the city, and they will be instrumental in the first phase. From their elevated positions, the Kurds will try to advance down through the Nineveh plains and toward Mosul. In doing so, they will not only tighten the perimeter around the city but also divert the Islamic State's attention and resources and open alternative lines of advance into Mosul. While the peshmerga handle most of the fighting in the first phase — with help from their allies and the Iraqi security forces — the bulk of Iraq's manpower will move toward Mosul from positions in the south along highways 1 and 80 on either bank of the Tigris. Iraqi commando units and special operations forces will play a prominent role in spearheading the offensive from the south and in helping the peshmerga in key areas.
Two secondary operations can also be expected during this phase. The first will try to constrict the Islamic State-controlled Hawija pocket southeast of Qayyarah and east of Highway 1, from which the militant group could launch attacks on key Iraqi logistics lines leading into Mosul. Pushing back the Islamic State positions from the Tigris River would also help draw forces from defending critical supply lines. Advances toward the Adaya, Atsan and Zambar mountains are also likely, putting pressure on the Islamic State's last supply lines to Mosul. The predominantly Shiite Popular Mobilization Forces will likely play a central role in both operations, which will give them an important mission while avoiding conflict that could arise with the local Sunni population in Mosul.
Beyond these campaigns, secondary operations in the north — including strikes on Tal Abta, Tal Afar and its air base, and the villages south of Sinjar — could also figure prominently in the overall battle for Mosul. Such missions would force the Islamic State to dilute its forces and send reinforcements to other areas, depriving Mosul of additional units. For the coalition fighting against them, the fewer Islamic State fighters in the dense urban terrain of the city, the better.
With this in mind, Iraqi security forces will also have to decide whether Mosul should be fully or partially encircled in the first phase. In several previous battles to seize key urban areas from the Islamic State in Iraq and Syria, advancing forces have made a deliberate choice to leave an escape route open. The reasoning behind this is that fighting the Islamic State in the open is far preferable to fighting the group in the confines of a city. Not only is urban fighting more difficult, but it is also destructive, something the coalition would rather avoid as much as possible in Mosul, given its large population and historical importance. At the same time, in some instances, such as the recent battle for Manbij, the Islamic State has used the gap not to withdraw but to bring in reinforcements. In the initial advance to Mosul, the coalition will likely leave an escape route open. If the Islamic State does not withdraw, however, the Iraqi security forces and peshmerga will be quick to close it.
A Long, Slow March
The first phase of the fight to retake Mosul will probably unfold over a period of many days, if not weeks. As the coalition advances on the city, the Islamic State will attempt to stall it and inflict casualties, particularly through the use of improvised explosive devices and ambushes. The group may even make a few determined stands, especially in key towns throughout the Nineveh plains. But the Islamic State will save the majority of its forces for the battle for Mosul itself, taking advantage of the challenging urban terrain and the defenses it has built up there. In addition, by taking positions among the city's civilian population, the Islamic State fighters there will minimize the threat of airstrikes.
As with any difficult and complicated battle, much could go wrong in the expansive operation to take back Mosul. Coalition infighting is especially a risk in light of the various groups that the conflict has brought together. We will be tracking the battle closely as it evolves and moves toward Mosul.