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Sunday saw the deadliest attack on US forces in the Middle East since the beginning of Israel’s war on Gaza. An overnight drone attack killed three US soldiers in a Jordanian base and injured dozens more. 

US President Joe Biden has promised to hold the perpetrators to account “at a time and manner of our choosing” - but experts have told ������ that preventing future attacks by the groups thought to be involved is no easy feat.

that the attack was launched by forces of the Iraq-based Kataib Hezbollah militia operating out of Syria. Kataib Hezbollah is one of the most powerful in a network of Iraqi Shia militias operating under the umbrella of the Popular Mobilisation Forces (PMF) and one of the PMF’s groups with the closest ties to Iran. Tehran has denied any involvement in the attack.

Even before the Gaza war started, PMF-affiliated groups like Kataib Hezbollah had carried out hundreds of attacks on US forces in the region. Political violence monitor ACLED recorded over 500 events involving these militias or one of their facade groups between June 2019 and March 2023. Since the Gaza war, these attacks have become a near-daily occurrence.

To understand the difficulty in preventing these attacks, it’s essential to recognise the complexities of these militias, moving beyond the pervasive designation of “Iran-backed” to explain their actions.

“The PMF are all, more or less, independent and autonomously acting militias. Even those that have a higher degree of Iranian support are still acting with quite a large degree of agency,” Andreas Krieg, Director of strategic risk consultancy MENA Analytica, told ������.

“In the PMF infrastructure, there are some groups that are not at all Iran-affiliated, some of them are very closely Iran affiliated, and some I would consider - for example, Kata’ib Hezbollah - to be a semi-Iranian entity, because they are also staffed by Iranian fighters or have fighters embedded in them from the Quds Force or other IRGC entities,” he added.

“It would be too easy to say that all PMFs are Iran-affiliated, as people always say.”

Krieg explained that the roots of these networks run deep, with interpersonal and ideological relationships cementing ties between the Iraqi groups and their allies in Iran.

Some of these relationships pre-date Iran’s 1979 Islamic Revolution. Others, like that of the Badr Organisation - one of Iran’s most powerful allies in Iraq, boasting political influence in the highest echelons of the Iraqi government - date back to the Iran-Iraq war.

Because of that history, Krieg said, “It’s not necessarily a top-down relationship. Even if money, equipment, advice, and training come from Iran, these groups don’t necessarily follow Iranian orders in black and white - but they do seek Iranian approval when they act”.

He explained that they will often carry out attacks to demonstrate to a domestic audience their legitimacy and their actions in championing the pan-Shia or Palestinian cause.

“When a militia attacks a US interest or a US base, that will be something that requires approval from Iran, but it doesn’t mean that Tehran is pushing them or ordering them to conduct attacks,” Krieg added.

That means Sunday’s fatal attack, if it was carried out by Kataib Hezbollah or another PMF militia, likely had the direct approval of Tehran.

Ending the PMF’s attacks on US troops and ensuring Iraq does not fall further under Iranian influence is no easy feat, according to Ali Bakir, Non-Resident Senior Fellow at the Atlantic Council's Scowcroft Middle East Security Initiative and Middle East Programs. 

He told ������ that any strikeback against the PMF could end up helping them. “Tactical reactions will not deter these militias. On the contrary, they are likely to create a supportive base for them, rebrand them as resistance, and popularise them,” Bakir said.

Instead, he explained, “There is a need for a long-term strategy that empowers their opponents, involves cooperation with regional heavyweights against them, and most importantly, addresses the Iranian factor. In other words, the most effective approach would be to deter Iran itself, rather than keeping occupied with its proxies”.

Bakir views the PMF militias as more closely controlled by Tehran. “These militias essentially function as extensions of the IRGC in Iraq, deeply intertwined with the state and serving Iranian interests while hindering Iraq's autonomy,” he said.

“If the US and UK want to deter these militias, it must address its relationship with Iran in parallel with applying pressure on them; otherwise, the cycle of conflict will persist,” he added.

The PMF’s factions, and Iraq’s wider Shia bloc, are subject to internal competition, power plays, and ideological differences, including vis-à-vis their relations with Iran. This could be their weak spot.

Andreas Krieg explains that the horizontal nature of the PMF network means that the network as a whole is extremely resilient and no one node has too much power over others. Instead, they compete within the network for influence. Some have pointed to , including former members of the PMF.

While Krieg argues that competition of this nature is mostly “healthy” for the PMF network’s influence and resilience, it can and does flare up into violence.

In January, for example, a between rival PMF militias at a commemoration service for former IRGC Quds Force Commander Qassem Soleimani and former Kataib Hezbollah Secretary General Abu Mahdi al-Muhandis, both of whom were killed in the same US airstrike. 

Both groups involved - the Badr Organisation and Kataib al-Imam Ali - are associated with the PMF network. Competition over business interests and the perceived legitimacy of their operations means their relations are fraught. 

Nader Hashemi, Associate Professor of Middle East and Islamic Politics at Georgetown University, highlighted the 2019 Iraq protests as an example of how the country’s intra-Shia relations (of which the PMU and associated militias are an integral part) are becoming increasingly important in the political fabric of modern-day Iraq.

“At the end of 2019, so just before the pandemic, you saw a series of citizens’ revolts throughout the region protesting the same set of issues: the corruption of the ruling elites, the absence of public services, poverty, discontent,” Hashemi told TNA.

“This happened, critically, in Baghdad where there was basically a citizens' revolt led by the poor Shia Muslim young people against the political parties, which are also dominated by Shia parties and their allied militias.”

The Iraqi Parliamentary Human Rights Committee reported that at least 319 people had been killed during the protests. Kataib Hezbollah was alleged to be involved in the suppression of those 2019 demonstrations, which also saw Qassem Soleimani visit Baghdad and Shia protestors targeting Iranian consulates for their perceived meddling in Iraqi affairs.

“In that moment, it was an intra-Shia Iraqi feud over the question of corruption, representation, employment - and Iran was on the side of the establishment ruling parties,” Hashemi said.

Chris Hamill-Stewart is a freelance journalist and writer specialising in the business and politics of the Middle East and the Islamic world. He speaks regularly on current affairs in the UK.

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