Iraqi Popular Mobilisation Forces (PMF) deputy head Abu Mahdi al-Muhandis, killed early Friday (January 3rd) in a US strike on Baghdad, was seen as Tehran's man in Iraq and a sworn enemy of the US.
The US strike on Baghdad's international airport early Friday also killed his personal friend Maj. Gen. Qassem Soleimani, commander of the Islamic Revolutionary Guard Corps Quds Force (IRGC-QF), and PMF public relations leader Mohammed Ridha Jabri.
The men died in a strike on a convoy belonging to the PMF, an Iraqi paramilitary force with close ties to Iran.
It came just days after PMF supporters attacked the US embassy in Baghdad, provoking anger in Washington.
Al-Muhandis -- the widely-used nom-de-guerre for Jamal Jaafar Ibrahimi -- was among the pro-Iran mob laying siege to the embassy on Tuesday.
"Al-Muhandis was demonstrative of how Iran built its network of proxies in Iraq," said Phillip Smyth, a researcher focused on Shia armed groups.
"He has history with basically every major network Iran had in Iraq. You would not have found a stronger ideal" of Iran's influence in the country, he said.
A native of Basra, al-Muhandis was born to an Iranian mother and an Iraqi father in 1953. He settled in Iran in 1979, and became a military advisor to the IRGC-QF. In the 1980s, he also served as a commander in the Badr Corps.
He was sentenced to death in absentia in Kuwait for his involvement in the 1983 bomb attacks on US and French embassies there.
Founder of hardline militia
Al-Muhandis briefly served as an Iraqi MP following the 2005 elections.
He then helped found Kataib Hizbullah -- a hardline Iran-backed militia that targeted US troops.
On December 4th, members of the militia attacked peaceful Iraqi demonstrators who have denounced Tehran's role in their country.
In 2009, the US sanctioned both al-Muhandis and Kataib Hizbullah as "terrorist" entities.
Washington said al-Muhandis ran "weapons smuggling networks and participated in bombings of Western embassies and attempted assassinations in the region".
Michael Knights, an expert at the Washington Institute, described al-Muhandis as "the most inveterate opponent of the US" among Iraq's Shia armed groups.
He was later appointed deputy head of the PMF, founded as a loose network of factions fighting the "Islamic State of Iraq and Syria" (ISIS) in Iraq.
The PMF was later absorbed into Iraq's formal security forces, but some of its more hardline factions, including Kataib Hizbullah, still operate independently of Baghdad.
'Central nervous system of IRGC-QF in Iraq'
"Al-Muhandis worked assiduously to develop the PMF into an organisation that was neither subject to full prime ministerial command nor subordinate to the conventional security forces," said Knights.
Although he worked under Faleh al-Fayyad, also Iraq's national security advisor, al-Muhandis was widely recognised as the PMF's "real" leader, observers said.
He had both the utmost loyalty of its forces on the ground and control over its financial resources.
That made him "the central nervous system" of the IRGC-QF in Iraq, Knights wrote last year.
He was a personal advisor to Soleimani, with the two pictured on multiple occasions in warm embraces.
Despite his high-profile position within the PMF, al-Muhandis rarely appeared in public or delved into politics.
It remains unclear who could replace him, Smyth said, as it would be challenging to find someone with such a close ideological and personal relationship to Iran.