Abu Mahdi al-Muhandis, one of the most powerful militia commanders in Iraq, was killed in the same US air strike that eliminated the Iranian spymaster Qassem Soleimani and pushed Washington and Tehran to the brink of war. At the time, as the US and Iran exchanged threats of mutual destruction, little attention was paid to the death of the 66-year-old Iraqi fighter, for years a thorn in Washington’s side. But as the dust settles on the first round of Iranian retaliation, Iraqi officials and Western experts warn that Muhandis’ killing has rocked Iraq’s powerful network of Shia militias, weakening Iran’s influence in the country but increasing the risk of militia violence and reprisals against US targets.

Born in Basra, Muhandis led Kata’ib Hizbollah, one of the most radical Iran­ backed paramilitary groups, through which Tehran has dramatically increased its influence in Iraq over the past decade. In 2017, hewas appointed as the deputy commander of an umbrella paramilitary group, the Popular Mobilisation Forces, created as Baghdad sought to bring the myriad militias that fought against Isis under the command of the armed forces.

The PMF now stands at some 140,000 salaried militiamen and boasts one of the largest blocs in parliament, the Fatah coalition. But the backbone of the group remains battle-hardened Shia militias, trained and funded by Tehran, who previously fought American troops in Iraq and call themselves “resistance groups”. Muhandis, a nom de guerre meaning “engineer”, “orchestrated primarily the resistance camp, the pro-Iranian group”, and was a close ally of Tehran for decades, said a senior Iraqi official.