An anonymous source at U.S. Central Command recently released the details of the battle plan and organization of forces that the United States and its partners are aiming for, with the goal of launching the offensive by April or May. The details outline a plan for an Iraqi security force consisting of 20,000-25,000 troops to advance from the south to retake Mosul while Kurdish peshmerga forces contain the city from the west, north and east.
Phase One: Train Troops and Contain the City
The first phase comprises the training of appropriate troops and the containment of Mosul. Many steps have already been taken toward executing this phase: The peshmerga forces have maintained steady offensives around Mosul while cutting off the city's main supply line from Tal Afar, and the United States and its coalition partners have been training Iraqi troops. However, the training is far from complete.
Pulling together a unified force of disparate fighters numbering in the tens of thousands within a month is ambitious, to say the least, particularly when many of these groups collapsed last year and hold conflicting interests or historical enmity toward each other. Washington has been quite vocal about taking the time needed to accomplish this goal before launching the offensive against Mosul, but Baghdad — facing pressure from its citizens to show that the army is winning the fight against the Islamic State — has been pushing for the fight to begin as soon as possible.
The composition of the fighting force also poses an issue for planners. While the peshmerga, Iraqi army, Shiite militias and some Sunni tribal elements have been able to work together without too much friction thus far, the overuse of such forces in proximity to each other could result in infighting and collapse. A mixture of Sunni tribal forces and Shiite militias would be especially volatile, and one that the U.S.-led coalition seems to be trying to avoid by having them work in separate areas. In the case of Mosul, these groups have been excluded entirely; instead, planners rely on peshmerga forces to block in the city and conventional Iraqi forces to form the maneuver element.
Phase Two: Push North and Seize Mosul
Regardless of the difficulties or pitfalls in Phase One, certain events must happen on the ground before the offensive can begin. First, training must be completed and forces must be shipped north toward Mosul itself. Because the Islamic State holds multiple towns and villages south of Mosul along the Tigris River Valley, it remains to be seen how military planners will address those areas in their plans. One option would be to contain enemy forces within the cities while allowing the main force to bypass them and head straight for Mosul. While this tactic would save time, it would also cost manpower that could not be used in the main battle. Another option would be to methodically clear the valley and displace Islamic State fighters from all of their positions. This would preserve a larger force for the battle at Mosul, but it would likely cost time and lives. One of these options must be implemented to protect the supply lines and flanks of the forces that take Mosul, and until a large force arrives at the city's doorstep, no serious offensive can begin.
It is important to note that the start of the offensive matters little compared to its end. The operation will be successful only if it can cut off and destroy a portion of the Islamic State's forces, thus degrading the group's ability to wage war in the broader region. Merely displacing Islamic State fighters from the city will carry little to no gain, since they have already reaped many resources from Mosul and would be valuable additions on the Islamic State's many other fronts. Given the Iraqi forces' performance in other urban conflicts in Ramadi and Fallujah, it is very possible that Mosul will become a conflict in which forces on either side grind statically against each other, imposing large costs with little definitive achievement in sight. To avoid this, planners and trainers need to take the time to thoroughly prepare — a sentiment regularly echoed by U.S. military officials.
Phase Three: Occupy the City
Once Iraqi forces take Mosul, Phase Three will begin: occupation. How, and with which forces, Baghdad decides to reassert control over and manage Mosul matters. The Kurdish peshmerga and largely Shiite Iraqi troops will still be at odds with the city's Sunni Arab population long after the Islamic State is gone. Planners will therefore likely make an effort to arrange for a Sunni force to take charge in the interim. Such a force could be drawn from a Sunni-dominated Iraqi army or police unit, or perhaps the Sunni National Guard that may be formed from Sunni tribal forces, though this idea has gained little traction so far. Much of the success during this phase will depend on the relationship between the Sunni tribes and Baghdad, and on the broader political accommodations they must reach regarding political and military power as well as the allocation of resources moving forward. To date, Sunni tribes' willingness to work with Iraqi authorities against the Islamic State has been tepid at best, but Mosul's population will likely see any non-Sunni troops as an occupying force, which would mean that many of the same dynamics that allowed a Sunni militancy to seize control of Mosul could easily re-emerge.
For now, any talk of a planned offensive against Mosul is just that until a substantial force structure is moved into place. In a war involving so many different actors that could take years to resolve, battlefield realities could easily delay or cancel any potential push for the city as other, more pressing concerns arise. Still, the United States seems determined to work with its partners to retake Mosul by year's end despite the fact that several fundamental questions remain unanswered.