More than two weeks ago, the Iraqi government — such as it is — announced that they had begun the final “decisive” push to take Tikrit away from ISIS. That announcement could just as well have been made from Tehran, as Iranians comprised the bulk of the forces. For that reason, the US did not participate in the offensive with air cover, preferring not to act as Iran’s air force while Tehran dug its claws deeper into Iraq.

That was then. This is now:

U.S. warplanes began striking Islamic State forces in and around the Iraqi city of Tikrit on Wednesday, drawing the United States directly into a battle that has pitted the militants against Iraqi forces dominated by Iranian-backed militias.

Pentagon officials said that the Iraqi government had requested the assistance as the fight for Tikrit stalled as it moved into its fourth week. They said initial targeting for the strikes will be aided by U.S.-led coalition surveillance aircraft that recently began flying over the city, 110 miles northwest of Baghdad.

The fight for Tikrit is considered a crucial test for larger future objectives, including Mosul, Iraq’s second-largest city, which has been the symbol and center of Islamic State power in Iraq since the militants took it last summer.

But the Tikrit operation is fraught with potential political and strategic complications for the Obama administration. The overwhelming presence of Shiite militias and volunteers armed and advised by Iran has given rise to fears that their victory would promote sectarian divisions and bloodletting in the majority-Sunni city. U.S. officials have estimated that these Shiite fighters outnumber official Iraqi security forces and Sunni tribal forces by about 5 to 1 in the battle.

In other words, it’s an Iranian seizure of Tikrit, one that will put the Sunni city in Shi’ite hands — assuming they can succeed, by the way, which they’ve been unable to do until now. That’s exactly the outcome that Sunni tribes in Iraq feared when we pulled out in 2011 and allowed Nouri al-Maliki to purge and persecute Sunnis and Kurds. That’s why those Sunni tribal leaders that backed us in 2006-7’s Anbar Awakening have either ended up aligning with ISIS, or ended up dead.

Now that the US has thrown in with the Iranians on Tikrit, the issue of building a ground coalition of Sunni Iraqis and other Sunni nations might be a lot more complicated. The Kurds in the north, who generally get along better with the Iranians than the Sunnis do, may still be wondering why the US is now backing the Shi’ites that pushed them out of governance. The only way to defeat ISIS is to marginalize them among the Sunnis, just as we did with the Anbar Awakening. By allying with Iran, even for a one-time tactical advance, we’re playing right into the hands of ISIS.

The US insists that Iran’s assistance isn’t indicative of the direction in which Iraq will go over the long term:

Washington had expressed strong reservations over the leading role played in the Tikrit operation by Shiite militia groups, some of which have been accused of serious abuses.

Iran’s top commander in charge of external operations, Qassem Suleimani, has been ubiquitous on the Salaheddin front lines and is perceived by many Iraqis as the brain behind Iraq’s ground operations.

But at a briefing on Wednesday, Pentagon spokesman Colonel Steven Warren insisted Washington remained Baghdad’s most precious partner in the war to reclaim the vast regions of Iraq IS conquered last summer.

“Reliable, professional, advanced military capabilities are something that very clearly and very squarely reside with the coalition,” he said.

Of course, that excludes effective ground forces, which is what Baghdad desperately needed to get its territory back from ISIS. The US-led coalition hasn’t provided them, so Baghdad reached out to Tehran, which is delighted to get its footprint back in Iraq, especially in Saddam Hussein’s birthplace. Consider what a propaganda coup that will be for the mullahs in Iran, and how long they can exploit that to further legitimize their radical Islamist regime. This is a failure on multiple levels, and the Obama administration seems determined to remain either ignorant or dishonest about the long-term impact of its policies in the region.