An assault is underway in Iraq aimed at liberating the city of Tikrit, Saddam Hussein’s former hometown, from the control of Islamic State forces. If it is a successful operation, it would be a major victory in the war against ISIS in Iraq. But it is unclear if it would be an Iraqi triumph or another coup for Iran in its quest to carve out a buffer zone within the Iraqi state.

Prime Minister Haider al-Abadi declared the start of the Salahuddin operations on Sunday during a visit to the government-held city of Samarra, where some of the thousands of troops and Shi’ite militia had gathered for the offensive.

The pace of their progress in Salahuddin will affect plans to recapture Mosul further north. A U.S. official said the assault on Mosul, the largest city under Islamic State control, could start as early as April but Iraqi officials have declined to confirm that timetable.

In Salahuddin, Islamic State fighters control several strongholds including Tikrit, hometown of executed former president Saddam Hussein and other Tigris river towns.

A source at the local military command said forces advanced north from Samarra toward the town of al-Dour, which officials describe as an Islamic State bastion, and Tikrit, which lies about 40 km (25 miles) north of Samarra.

The assault represents the largest Iraqi operation yet undertaken to liberate portions of the country that have been occupied by ISIS fighters. Approximately 30,000 troops will be tapped to retake the Sunni-dominated cities north of Baghdad.

The assault on Islamic State positions will be conducted by Iraqi Security Forces, Shia militias who are as loyal to Tehran as they are to Baghdad, and a series of Sunni tribal groups that are only loyal to themselves. That is leading many to question whether this is an Iraqi or an Iranian mission.

If this loose alliance of convenience is successful in the effort to oust ISIS from the areas they now control, what comes next will not be an orderly return to the status quo ante. Many fear that these groups will eventually turn on one another. Still more are concerned that the Shiite-dominated forces working to oust ISIS will be as or more brutal on the Iraqis who remain in these areas than were their Islamic State occupiers.

Finally, as Ali Khedery observed in an extensive analysis published in Foreign Policy, the Obama administration’s decision to favor expediency and disengagement has sown the seeds of a renewed and horrible sectarian conflict that will engulf not merely Iraq but the entire region in the wake of ISIS’s ultimate defeat.

When it became clear that the Islamic State posed an existential threat to Iraq’s Shiite-dominated government, the country’s top Shiite cleric, Grand Ayatollah Ali al-Sistani, resorted to a measure not taken in a century: He issued a religious edict calling for all able-bodied men to take up arms to defend the state. Within months, hundreds of thousands of young Shiites responded to the call — and today, virtually all of them have been absorbed into Iranian-dominated militias, whose fundamental identity is built around a sectarian narrative rather than loyalty to the state. Recently, one militia commander estimated their total strength at 800,000 men, dwarfing the official Iraqi Security Forces.

Meanwhile, the Iranian Revolutionary Guard Corps’ Quds Force, Iran’s special forces unit devoted to operations outside the Islamic Republic’s borders, has filled the void left by Obama’s military and diplomatic disengagement from Iraq. Quds Force commander Gen. Qassem Suleimani has personally led operations from the front lines, buttressing decades-old alliances while at the same time cultivating new proxies.

This constellation of Iranian-backed militias is eclipsing official Iraqi institutions, and sowing the seeds of conflict for decades to come. During a January 2015 press conference celebrating the “liberation” of Iraq’s Diyala province, Ameri stood in front of Iraqi military officers and militia fighters, thanking the Badr Organization and AAH for their efforts — without once mentioning Prime Minister Abadi or the international coalition. One of Ameri’s Badr commanders then told the New York Times that Sunni tribes had backed IS, and pledged that “their punishment will be more severe than [IS’s],” guaranteeing the continuation of vigilante justice and sectarian bloodletting.

This is just more evidence indicating that President Barack Obama’s highest priority for the war in Iraq and Syria against ISIS is not to resolve that conflict but to contain it for long enough so that he can leave office without having to commit American forces to the fight. The post-ISIS environment in Iraq and Syria is likely to be a chaotic one, and the next American president will be perfectly justified in casting blame on the 44th President for failing to secure a sustainable peace in that part of the world.