Despite his short stature and quiet demeanor, Qasem Soleimani was considered one of the most infamous military operators in the Middle East by the United States and its allies.

As leader of the Islamic Revolutionary Guard Corps’ elite Quds Force, the 62-year-old bore responsibility for Iran’s clandestine operations abroad, quietly extending the military reach of Iran deep into foreign conflicts such as those in Syria and Iraq.

In the process, he earned himself near-mythical status among his enemies and idolization by his Iranian hard-line supporters.

Analysts have complained that Soleimani had more diplomatic clout than Iranian Foreign Minister Mohammad Javad Zarif and pondered whether he would eventually seek top political office. Some compared him to Karla, the fanatical, but fictional, Soviet spymaster in John le Carré’s Cold War novels.

But his story came to an end late Thursday when a U.S. airstrike near the Baghdad airport killed him and a number of Iraqi militia leaders.

Soleimani’s career began soon after Iran’s 1979 revolution and helped shape the Islamic republic that followed it.

“More than anyone else, Soleimani has been responsible for the creation of an arc of influence — which Iran terms its ‘Axis of Resistance’ — extending from the Gulf of Oman through Iraq, Syria, and Lebanon to the eastern shores of the Mediterranean Sea,” Ali Soufan, a former FBI agent and national security analyst, wrote in a 2018 profile.

A young man from a poor family in Iran’s mountainous southeast, Soleimani joined the Islamic Revolutionary Guard Corps, a group designed to protect the new republic and enforce its strict ideological aims.

During the war with neighboring Iraq from 1980 to 1988, the Revolutionary Guard gained political and economic power. The bloody and brutal war in Iraq also helped shape Soleimani.

Only in his 20s, he undertook missions behind enemy lines, the sort of irregular warfare that would one day become the calling card of the Quds Force.

He also found allies among Iraq’s majority-Shiite population, some of whom backed Iran against the Sunni-dominated dictatorship of Saddam Hussein.

In the late 1990s, Soleimani was given control of the Quds Force, the wing of the Revolutionary Guard devoted to external affairs. The group had a lengthy history, having helped establish Hezbollah in Lebanon in the early 1980s, and under Soleimani’s watch it expanded its influence in the region.

After the U.S.-led invasion of Iraq ousted Hussein, the Quds Force began to aid Shiite militias in the country as they fought American troops. A recent Pentagon estimate said that Iranian proxy forces killed at least 608 U.S. troops in Iraq between 2003 and 2011.

Later, in the Syrian civil war, a massive intervention by the Quds Force helped turn the course of the war in favor of President Bashar al-Assad, a regional ally of Tehran’s.

Soleimani’s influence was most keenly felt in the Middle East, but his practical ambitions were not regionally bound. The Quds Force was linked to plots in Asia and Latin America, and even one failed 2011 attempt to assassinate Saudi Arabia’s ambassador to the United States at an Italian restaurant in Georgetown.

After President Trump pulled the United States out of the 2015 nuclear deal between Iran and other world powers, the Quds Force found itself at the center of rapidly escalating tensions with the United States.

In Iraq, Shiite militias harassed U.S. troops, firing rockets at bases used by Americans. After one attack in late December killed a U.S. contractor, the United States launched airstrikes against bases along the border with Syria used by the group Kataib Hezbollah, killing 25 militia members and injuring more than 50.

On New Year’s Eve, Shiite militias and their supporters stormed the U.S. Embassy compound in Baghdad. Although no one was killed in the chaos, Trump warned that Iran bore responsibility for the act. “They will be held fully responsible,” he tweeted.

The airstrike Friday morning killed not only Soleimani but also Jamal Jaafar Ibrahimi, an Iraqi militia commander better known by his nom de guerre, Abu Mahdi al-Muhandis.

Analysts agreed that Soleimani was a unique figure and probably irreplaceable for the Iranian regime. But after the shock of the news of his death, some wondered what effect killing such a revered figure would have on the region.

“The pressure to retaliate will be immense,” Vali Nasr, an expert on the Middle East and a professor at Johns Hopkins University, observed on Twitter.