Within hours of the United States assassination of Qassem Soleimani, a top general in Iran's Islamic Revolutionary Guard Corps (IRGC), the country's Supreme Leader named a successor to head the elite Quds Force he had commanded.

Ayatollah Ali Khamenei's choice of Esmail Qaani, who served as Soleimani's deputy for more than a decade, was aimed at ensuring a smooth and swift transition in the strategic foreign unit's leadership at a time of heightened tensions between Washington and Tehran, according to analysts.

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Soleimani's assassination in a US air strike in Baghdad on January 3 pushed the US and Iran to the brink of war, but fears of an all-out conflict eased when retaliatory Iranian strikes against US targets in Iraq on January 8 concluded without any fatalities.

Khamenei has since called for the expulsion of US troops from the region.

Under Soleimani, dubbed Iran's "shadow commander" by some media, the Quds Force helped boost Iranian influence across the Middle East by building up a vast network of proxies.

In Syria, the unit played a key role in shoring up support for embattled Syrian President Bashar al-Assad after the country descended into war in 2011. It also armed and trained militias that helped defeat the ISIL (ISIS) armed group in both Syria and Iraq.

'Loyal, committed'

Khamenei, announcing Qaani's appointment on January 3, said the Quds Force's new chief was "among the most prominent IRGC commanders" during the 1980-1988 war between Iran and Iraq, adding that the unit under the veteran soldier will follow an "identical" strategy to that pursued by Soleimani.

At the slain commander's funeral days later, Qaani pledged to continue on his predecessor's path "with the same force", saying his assassination "will be reciprocated in several steps by removing the US from the region".

Saeid Golkar, a professor of political science at the University of Tennessee in the US, said for Khamenei, it was important that the new head of the Quds Force was "loyal" and "committed" to himself and the IRGC. "Familiarly with the Quds Force and the ability to manage the forces and Iran's proxies were important [traits]," he added.

Qaani fit that bill.

Before his appointment, General Esmail Qaani was the second in command as the deputy head of the elite Quds Force [File: Iranian leader press office/Anadolu]

Born in the late 1950s in the city of Mashhad in northeast Iran, Qaani joined the IRGC in 1980, a few months before Iraqi forces invaded western Iran, triggering a bloody eight-year-war which killed about a million people.

It was in March 1982, on the war's front lines, that Qaani befriended Soleimani, according to Ali Alfoneh, an expert on IRGC and senior fellow at the US-based Arab Gulf States Institute.

Indeed, Qaani has described his camaraderie with Soleimani as one that was forged during war.

"We are war comrades, and it was the war that made us friends," he was quoted as saying by the government-funded IRNA news agency in a 2015 interview. "Those who become friends at times of hardship have deeper and more lasting relations than those who become friends just because they are neighborhood friends."

Alfoneh said that it was also during the war that Qaani met Khamenei, who was Iran's president at the time. IRNA published a photo of Khamenei and Qaani, which the Iran Wire news website said dated to 1986.

Esmail Qaani was #QasimSoleimani's deputy in the Quds Force. Like Soleimani, he was a revolutioary guards commander during the 1980-88 Iran-Iraq War. Qaani (second from right) in this picture from, circa 1986, with then president and now leader @khamenei_ir (with glasses) #Iran pic.twitter.com/c1Y1mlsrl9 — IranWire (@IranWireEnglish) January 3, 2020

Soon after the war, Qaani was appointed as deputy chief of the IRGC's ground forces. According to Alfoneh, he likely played a lead role in the IRGC's operations against drug cartels in Afghanistan and in its support to the Northern Alliance, which fought to contain the Taliban in the 1990s.

Although it is unclear when Qaani joined the Quds Force, IRNA said he was appointed as the unit's deputy in 1997, the same year that Soleimani was named as its commander. But according to Maysam Behravesh, a Sweden-based political analyst at Persis Media, that appointment came years later, in 2007.

'In the shadows'

With a clear division of labour and maintaining geographically distinct spheres of influence, Soleimani and Qaani together played a strategic role in expanding Iran's influence in neighbouring countries.

"While Soleimani was a national icon and the charismatic leader mobilising the masses behind what he and the Islamic Republic perceive as a sacred cause, Qaani constantly attended to the organisational and administrative needs of the Quds Force in the shadows," Alfoneh said.

"Soleimani also spent more time in western Iran, while Qaani spent most of his time in eastern Iran. As a consequence of this, Qaani's professional focus was on the Pakistani and Afghan Shia, but also [other] allies in Central Asia," he added.

In the few public statements Qaani has made, he has slammed the US and Israel, saying in one 2017 article that US President Donald Trump's "threats against Iran will damage America".

"We have buried many … like Trump and know how to fight against America."

Behravesh said Qaani would bring the Quds Force greater continuity rather than change.

"The same policies are expected to continue, but perhaps with greater vigour and ruthlessness now that US maximum pressure on Iran seems to involve 'leadership decapitation'," he said.

Furthermore, even though the Quds Force's operations are more widely associated with Iran's direct neighbours in the Middle East and Asia, it may expand its activities beyond those regions under Qaani, said Behravesh.

"Qaani reportedly has good relations with like-minded African Muslim groups, which suggests the Quds Force under his command might seek to have a more active presence there," he told Al Jazeera.

In 2012, the US sanctioned Qaani, citing his role in financial disbursements to Quds Force's "elements in Africa" and other "terrorist groups".

Afshon Ostovar, assistant professor of national security affairs at the US-based Naval Postgraduate School, said the Quds Force's work in Afghanistan may also become more prominent.

"Given Qaani's personal experience in Afghanistan, he could make that country more of a focus than it was, but any change will probably be strategically marginal."

But Qaani's aversion to publicity was unlikely to change, with Ostovar saying: "Qaani's relative obscurity as a public persona is one of his defining characteristics ... He doesn't seek the spotlight, and the IRGC has not sought the spotlight for him."

Behravesh agreed. Pointing out that in addition to intelligence leaks, Soleimani's celebrity status may have contributed to his assassination, Behravesh said Qaani is expected to be Iran's real "shadow commander".

"The IRGC will do its best not to be bitten in the same spot again."

Follow Arwa Ibrahim on Twitter @arwaib