Islamic State will lose the Iraqi cities of Tikrit and Mosul.

Victory won’t come quickly or easily for the combined forces of the Iraqi government, Shi’ite militias, Kurdish fighters and Sunnis who have learned to loath Islamic State. But sheer weight of numbers, as well as Iranian and American military assistance, should do the trick.

Unfortunately, none of the parties involved in the fighting like each other very much. In Mosul in particular, beating Islamic State looks likely to set the situation back to April 2003, when an entire Iraqi army corps surrendered the city to a small American force. Fighting officially came to an end, but chaos ensued as the Kurds and Sunnis battled one another alongside Sunni and Shi’ite clashes. Crowds ransacked the central bank and pillaged the university library. During the subsequent U.S. occupation under General David Petraeus, a 21,000-strong force from the 101st Airborne pushed Kurdish militias out of Mosul and created an uneasy peace with the Sunnis.

After Petraeus left, however, multisided fighting resumed in Mosul, as the fundamental issue of which group truly controlled the city — a question that still haunts the country as a whole — was left unresolved. Islamic State was able to violently exploit that power vacuum to take the city last year.

The unfolding assault on Tikrit, Saddam Hussein’s hometown, is also a byproduct of the Sunni-Shi’ite struggle. The Sunnis held the city until 2003, then the Shi’ites until 2014, and now, of course, Sunni-aligned Islamic State. But unlike what is planned for Mosul, the force advancing on Tikrit is largely made up of Shi’ite militias, led by Iranian General Qassem Soleimani, who successfully directed militia campaigns against American forces in Iraq War 2.0. Unlike in Mosul, there will be no power vacuum once Islamic State is routed, but there will be blood.

Iraqi Prime Minister Haider al-Abadi has set the stage for ethnic cleansing of the city, warning, “There is no neutrality in the battle against [Islamic State]. If someone is being neutral with [Islamic State], then he is one of them.” Many fear Shi’ite militias will begin a slaughter inside Tikrit, as happened in once-Sunni Jurf al-Sakhar following a Shi’ite victory there over Islamic State.

A victory over Islamic State in Tikrit would empower Shi’ite militias and increase the Iraqi government’s reliance on them versus the American-trained army. It would solidify Iran’s influence over Abadi and further peel back the curtain to reveal the American war against Islamic State as little more than a stage for the greater Sunni-Shi’ite struggle.

In Mosul in particular, the Americans have painted themselves into a corner. They have promoted the fight as a set-piece battle that must be fought by all Iraqi sides, as if organizing the Allies ahead of D-Day.

According to one Pentagon briefing, the United States hopes by the end of the year to piece together 25,000 Iraqi troops, including three Kurdish brigades, an unspecified number of Shi’ite militiamen, as well as a currently nonexistent Sunni force made up of former Mosul police who would enter the city once Islamic State fighters are cleared out. The hope – and it is little more than a hope – is that that small Sunni police force would prevent bloodletting. Defense Secretary Ashton Carter now says unspecified parts of the briefing were inaccurate.

American ground forces will almost certainly be required to make the assault on Mosul work, as Iranian leadership is required for Tikrit. But in addition to calling in close air support, the United States will have to take on the additional task of coordinating the many disparate elements on the Iraq side.

Two questions about the upcoming battle of Mosul emerge.

Will U.S. forces have to destroy Mosul in order to save it? Urban warfare is one of the most devastating forms of combat. Look at the devastating toll in the fight to regain control of the Syrian city of Kobani from Islamic State. The United States led more than 700 air strikes on the town. Some 230,000 residents were forced to flee. The civilian death toll has never been calculated, and no plans to rebuild the city have been announced. As an anti-Islamic State activist in the militant group’s self-declared capital of Raqqa wrote: “People don’t look at Kobani and see a defeat because everyone had to leave and the Americans bombed it to rubble to win.” In Mosul, similar destruction is expected; the United Nations predicts that throughout the area, there will be some 1.5 million displaced persons in the aftermath of the fighting.

And then we return to the key question of who will control whatever is left of Mosul. American help against Islamic State will be welcomed by all sides. Reaction to American power-brokering afterward among the Sunni, Shi’ite and Kurdish communities is far less certain.

It seems highly unlikely that the Kurds, especially after shedding blood to retake Mosul, would simply walk away as a small police force of Sunnis moves into the coveted city. The Sunnis would be hard-pressed as well to give up easily, especially in the face of potential ethnic cleansing and score-settling. The Shi’ite-dominated Iraqi government would press the United States hard for control of the city as the legitimate rulers of Iraq. No one knows what card the Iranians might play, especially since the road to Mosul leads through Tikrit.

This is a slow-motion car wreck. In preparing to win its second battle for Mosul, the United States appears to be readying itself, once again, to fight the wrong kind of war in Iraq by focusing on military action while paying little attention to the complex underlying political, ethnic and religious factors that will surely, once again, snatch defeat from any victory.