While Iraqi Prime Minister Haider al-Abadi recently declared victory in Fallujah, there are still pockets held by the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) in the city. Regardless of these final military operations, there are two significant political dynamics that have been established.

First, the United States has had an uneasy relationship with the Iraqi Shia militias, otherwise known as the Popular Mobilisation Units (PMUs), since it began its air campaign against ISIL, yet close to exactly two years into conflict, it is these Iranian-sponsored forces that have become integral to Washington's efforts.

Fight for Fallujah: Iraqi forces on verge of retaking city from ISIL

Second, Ayatollah Ali al-Sistani, in his capacity as a respected cleric, has become embedded in Iraq's domestic politics. Yet the battle for Fallujah shows how he has leveraged his position to dictate military strategy and tactics.

Shia militias and the US

In June 2014, just a few days after the fall of Mosul, David Petraeus, the former commander of US forces in Iraq and architect of the "surge", issued a warning about the US siding with the Iraqi Shia militias.

I specifically recall the various headlines that emerged afterwards, such as, "Petraeus: US Must Not Become the Shia Militia's Air Force".


READ MORE: Iraq - the reinvention of Muqtada al-Sadr


The reason that those headlines resonated with me was because back then I knew Petraeus' admonition would go unheeded.

In Washington's view, the PMUs' potential to alienate Sunnis in Fallujah took precedence over the military effectiveness of the militias.

 

The US Air Force would become the Shia militias' air force because at that juncture there was no Iraqi air force or army to speak of. Given the US aversion to "boots on the ground" in Iraq, Washington would have to rely on the Shia militias, and the Shia militias would have to rely on the US Air Force. It was not exactly a match made in heaven, but a forced marriage.

The battle for Fallujah involved the regular Iraqi military and militias. To allay fears that the Shia militias would take the predominantly Arab Sunni city, Abadi announced that they would play a supporting role, and not participate in the assault on the city's centre.

The bargain was that if the militias were held back, the US would increase the tempo of its air strikes, as it did in the battle for Ramadi in December 2015.

In both cases, US air power was contingent on sidelining the Shia militias. In Washington's view, the PMUs' potential to alienate Sunnis in Fallujah took precedence over the military effectiveness of the militias.

Like in Ramadi, Iraq's Counterterrorism Forces and a thousand Arab Sunni tribal fighters led the assault into the centre of Fallujah, capturing ISIL's urban HQ.

Shia fighters and Iraqi security forces hold an ISIL flag, which they pulled down after clashes with ISIL north of Fallujah, Iraq [Reuters]

Regardless of whether it might have taken longer for Iraq's formal military to achieve this aim, or that it could have resulted in burn-out for the overworked Counterterrorism Forces, Washington still prioritised the political value of having a national Iraqi force secure the urban centres of Ramadi and Fallujah. 

Lesson from the Battle of Tikrit

Washington knows that the PMUs are central to any assault on an urban centre, whether they play a support role as in Ramadi, and now Fallujah, or take the city itself, as in Tikrit in April 2015.

Then the militias, most likely on Iran's order, boycotted the battle when the US was called in to conduct air strikes against well-entrenched ISIL positions.


READ MORE: A new formula in the battle for Fallujah


The militias complained in public statements then that the US would steal their glory and victory. In fact, the militias' advance had stalled after three weeks and it was American air power that turned the tide in favour of the PMUs.

Before the US committed its air force to the battle for Tikrit, General Lloyd Austin, the head of US Central Command, told the Senate Armed Services Committee on March 26: "I will not, and I hope we never, coordinate or cooperate with Shia militias."

Yet just close to a week earlier, his bosses, Army General Martin Dempsey, chairman of the Joint Chiefs of Staff, and Defense Secretary Ashton Carter, spent three hours in front of the Senate Foreign Relations Committee defending their management of the military campaign.

These officers, as well as the US Secretary of State John Kerry, repeatedly dodged questions from the senators about the length of time America’s commitment in the fight against ISIL would take. The consistent fear among policymakers and politicians has been the US commitment to a potentially open-ended campaign.

The Shia militias have become a pillar of the US achieving its war aims in a much shorter time span.

 

This debate within the Washington Beltway revolves around timing, and in this regard the Shia militias have become a pillar of the US achieving its war aims in a much shorter time span. The Iraqi military, despite the US-led training effort that has spanned more than two years, is still not in a position to take urban centres without the support role of the militias.

The Shia militias are allowing this campaign to unfold a lot faster, which is most likely on the mind of the American generals squirming in their chairs in front of Congress.

The role of Sistani

Sistani already played a military role in Iraq, calling for volunteers to rally to the defence of Baghdad in June 2014. In a statement in May, he urged the militias to show restraint against the civilian inhabitants of Fallujah in order to stave off abuses that happened when Tikrit fell.


READ MORE: What success would look like in Fallujah


In a second statement, he reiterated this plea, saying that "saving an innocent human being from the dangers around him is much more important than targeting and eliminating the enemy".

Sistani is not a general, but a cleric dictating military discipline on the battlefield. It is easy to forget he is Iranian. Sistani has also demonstrated, albeit subtly, that he is wary of the preponderant influence of the Islamic Republic and thus Ayatollah Khamenei in Iraq, via their proxies, the PMUs. This is a struggle between two Iranian Shia clerics over a Sunni city. 

In Fallujah, Iran and the militias learned their lesson on the need of US air support to defeat ISIL in urban combat. Iran and the PMUs will never admit this publicly, just as the US will not admit publicly that it owes a debt of gratitude to these militias.

Iran, the Shia militias, and the US are locked in a menage-a-trois to which they will never admit to, but it has become part-and-parcel of the region's geopolitics.

Ibrahim al-Marashi is an assistant professor at the Department of History, California State University, San Marcos. He is the co-author of Iraq's Armed Forces: An Analytical History.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.

Source: Al Jazeera