Iraqi forces along with Shiite militias and local tribes launched a major ground operation to retake Tikrit from Islamic State of Iraq and al-Sham (ISIS) militants. In the first day of the assault Iraqi forces killed at least 25 ISIS militants, according to a Shiite militia spokesman. "Most of the killed ISIS militants were Arab nationals not Iraqis. The majority of the militants retreated to central Tikrit," Karim al- Nouri al-Hashid, the al-Sha'bi Shiite militia's spokesman told Anadolu Agency. Iraqi security forces backed by Shiite militias have launched a ground offensive against ISIS on Monday to recapture Tikrit city, aiming to approach ISIS stronghold of Mosul. Tikrit, a Sunni-majority city, was the homeland of the deceased Iraqi leader Saddam Hussein.

Iranian general Qasem Soleimani, the chief commander of the Quds Force, the Revolutionary Guard's Special Forces that operate outside Iranian territory, arrived in Iraq on Saturday to serve as a military consultant to the Iraqi forces, according to the Iranian Fars News Agency. The U.S. however does not seem to be concerned about the Iranian involvement. The U.S. officials also said that Iraqi forces had not asked the U.S. to back them in Tikrit's ground offensive. Martin Dempsey, chairman of the Joint Chiefs of Staff, told members of the Senate Armed Services Committee that the U.S. respected Iraq's sovereignty and subsequently the manner in which Baghdad saw fit to defeat ISIS. Dempsey confirmed the existence of Iranian proxies in Iraq since 2004 and described their involvement in Tikrit as "the most overt conduct of Iranian support" but added that it should not be a problem if it did not lead to "sectarianism."

Glaringly absent are the U.S.-led coalition forces whose air campaign since last summer has nearly halted the ISIS rampage across Iraq. Pentagon spokesman Army Col. Steve Warren said this week that the U.S. is not providing air power in the Tikrit operation "simply because the Iraqis haven't requested us to." Liberating the city without the backing of coalition airstrikes will put Iraq's security forces to the ultimate battle-readiness test since any operation to recapture Iraq's densely-populated cities including Mosul and Fallujah will have to rely almost entirely on ground forces to minimize civilian casualties. However, more of a concern for the U.S.-led coalition is Iran's prominent role in the fight against the ISIS militants. Iran has long been influential in Iraq, but never so much so as over the past year, when the Iraqi military collapsed in the face of the militants' onslaught. Iraqi officials have noted Iran's quick response to their urgent requests for weapons and frontline assistance even as they accuse the coalition of falling short on commitments on the ground. The battle for Tikrit is likely to involve Iraq's first serious urban warfare challenge, involving street battles that Iraqi security forces are not trained for.