U.S. planes bombed several targets in the town of Tikrit in support of Iranian-controlled militias and elements of the Iraqi army.  Approximately 30,000 Iraqis have been stalled on the outskirts of Tikrit for more than a week as a few hundred Islamic State fighters controlled the center city.

Reuters:

The decision to give air support to the Tikrit campaign pulls the United States into a messy battle that puts the U.S.-led coalition, however reluctantly, on the same side of a fight as Iranian-backed militia in a bid to support Iraqi forces and opens a new chapter in the war.

It also appeared to represent at least a tacit acknowledgement by Baghdad that such airpower was necessary to wrest control of the hometown of former Iraqi dictator Saddam Hussein from Islamic State fighters, after its attempts to go it alone stalled.

Iraqi Prime Minister Haider al-Abadi said Iraqi forces would prevail with the support of "friendly" countries and the international coalition, including arms, training and aerial support.

"We have opened the last page of the operations," Abadi said on state television.

Reuters first reported the U.S.-led coalition's expected entry into the Tikrit campaign, disclosed by Iraq's president in an interview and later confirmed by a U.S. official. It has been carrying out strikes elsewhere in Iraq since August.

A U.S. defense official, speaking on condition of anonymity, said American warplanes and aircraft from allied nations were striking up to a dozen targets in Tikrit, selected after coalition surveillance flights.

A second U.S. official stressed that Washington in no way would coordinate with the Iranian-backed militia or seek to empower them in Iraq, even if those fighters might share the same narrow tactical objective as Iraqi forces in Tikrit.

In language that appeared to intentionally omit the Iranian-backed militia, Lieutenant General James Terry, the senior U.S. commander of the U.S.-led coalition, said the strikes were aimed at enabling "Iraqi forces under Iraqi command."

"These strikes are intended to destroy ISIL strongholds with precision, thereby saving innocent Iraqi lives while minimizing collateral damage to infrastructure," Terry said, using an acronym for Islamic State.

It doesn't matter how furiously they try to spin it; we are now a virtual arm of the Iranian air force.  More to the point, the Iraqis let loose a barrage of artillery and rocket fire that will almost certainly kill a lot of civilians.  Whom do you think the Iraqis are going to blame for civilian deaths?  U.S. bombs or Iraqi artillery shells?

Even more problematic is what the Sunnis are thinking.  Do they now see the U.S. as a Shia air force?  There are a lot of landmines that the U.S. is trying to avoid stepping on in this operation, and you wonder: if it's this bad in Tikrit, what will it be like in Mosul when they try to take back that city of 2 million?

The Sunni-Shia war for Islamic supremacy is spreading rapidly.  From Iraq to Syria to Libya to Lebanon to Yemen and flashpoints in between, we are witnessing something the world hasn't see in ages: a genuine religious war of extinction.  And we're helping fan the flames by allying ourselves with the Iranian Shias.