The “liberation” (as the Iraqis are calling it) of Mosul from the so-called Islamic State in Iraq and Syria (ISIS) has been anticipated for some time. Iraqi politicians, including Prime Minister Haydar al-‘Abadi, have promised to return the city to Baghdad’s control by the end of the year. I have said in the past that although they may be able to start the operation before the end of the year, I am not sure they will be able to complete the operation by then.

This could be a long, difficult, and bloody battle. ISIS has controlled Mosul since they overran the city in June 2014. They have had well over two years to prepare for what they know is their last major stand in Iraq.

Based on what we have seen in other cities held by ISIS and retaken by Iraqi forces, ISIS has developed a series of tunnels to allow the group to move men and weapons to where they are needed, as well as placed minefields, improvised explosive devices (IED) and other obstacles, mapped out ambush sites, and prepare scores of vehicle-borne IED’s with suicide drivers willing to confront attacking Iraqi forces. They will likely force civilians to be human shields as they have in other battles. ISIS has claimed that its fighters will fight to the death to defend the city. I believe them – ISIS fighters rarely surrender.

If and when ISIS is defeated in Mosul, it will only be a matter of time before it is completely eradicated or ejected from Iraq. I believe that given the forces arrayed against ISIS, and the resources dedicated to this operation, the Iraqis will ultimately be successful in retaking Mosul. The question is how much will it cost, in terms of time, resources, city infrastructure, and most importantly, human life.

According to Chairman of the Joint Chiefs of Staff U.S. Marine Corps General Joe Dunford, the Iraqi forces are ready for the operation in Mosul. All that is necessary is a political decision on the part of Prime Minister al-‘Abadi, which could come at any moment. I hope the general is right, but why did President Obama order another 1,100 U.S. troops to Iraq, remarking yet again that the Americans are not “ground forces,” but there to provide only “training and assistance, logistical support.”

Iraqi forces will include the Army, Air Force, Special Police and Counter-terrorism units, along with the Kurdish peshmerga and the Popular Mobilization Units (PMU). The PMU include Shi’a militias, as well as some Sunni, Christian, and Yazidi militias. Although Iraqi Air Force and Iraqi Army Aviation aircraft will participate, the bulk of air support will be provided by the US-led coalition (mostly U.S. Air Force).

The Iraqis must put an “Iraqi face” on this effort, that it is all Iraqis working together to liberate Mosul regardless of ethnicity or religious group. This will be critical after the city is cleared of ISIS.

As the Iraqis continue to push ISIS back into Syria (as well as out of the remaining areas under its control in the western Euphrates Valley), the real challenge will be reconstituting Iraq as a coherent nation. That means working with the Sunnis and Kurds to determine the future of the north – what areas now controlled by the Kurds might be included in the Kurdish autonomous region. For example, Kirkuk was taken from ISIS by the Kurds – I see no indication they are willing to give it up. It has always been the Kurds’ contention that Kirkuk is a Kurdish city – Baghdad does not agree.

The Iraqis must remove ISIS from Iraq – retaking Mosul is the key. Can the army that lost Mosul to ISIS in 2014 take it back from ISIS in 2016? They have to.