(NYTIMES) - The daring pre-dawn raid by US Special Operations forces in Syria that resulted in the death of the Islamic State In Iraq and Syria (ISIS) group's leader offered a vivid reminder that no matter how much the world might want to move on, the chaos in Syria continues to reverberate.

The sudden roar of US Apache attack helicopters in a pastoral patch of north-western Syria gave way on Thursday (Feb 3) to a firefight inside a three-storey building surrounded by olive trees.

The raid resulted in the death of the target, Abu Ibrahim al-Hashimi al-Quraishi, the largely unknown leader of ISIS, since 2019. US officials said he blew himself up and killed 12 others as commandos closed in.

Quraishi's death came days after US forces backed a Kurdish-led militia in a bloody, week-long battle to oust ISIS fighters from a prison in north-eastern Syria, the largest US combat assault on the group since the end of the militants' so-called caliphate three years ago.

That and the raid on Quraishi have highlighted that the US still cannot extricate itself completely from military engagement in Syria, and that its more than two-decade global fight against terrorist groups is far from over.

Here are five take-aways from the raid:

1. The US fight against terrorism grinds on, with no end in sight

Years of military action by the US and its international partners aimed at stamping out terrorism have exacted major tolls, first against Al-Qaeda and then against ISIS, which rose from the turmoil of the Iraq War and the collapse of the Syrian government. But even as an untold number of fighters have been killed and leaders eliminated, both groups have adapted into more diffuse organisations, adept at finding new havens from which to launch opportunistic violence.

The Taliban's takeover of Afghanistan this past summer, facilitated by the US military's withdrawal, refocused international attention on the prospect of terrorists regaining the country as a haven. In Iraq, ISIS recently killed 10 soldiers and an officer at an army post and beheaded a police officer on camera. In Syria, it has assassinated scores of local leaders, extorting businesses to finance its operations.

In Afghanistan, the withdrawal of US forces in August left the local ISIS affiliate to battle the Taliban, with often disastrous consequences for civilians caught in the middle.

"The recent attacks by ISIS," said Mr Mick Mulroy, a former top Pentagon official and retired CIA paramilitary operations officer, "indicate that ISIS is not done fighting, nor is the US and our partners."

2. As the US counterterrorism campaign evolves, commando operations remain rare

US efforts to combat terrorism around the world in recent years have been mostly defined by airstrikes and drone warfare, which have also exacted a huge - and largely unacknowledged - toll on civilians.

The raid against Quraishi was a reminder that the US military retains the ability to carry out targeted commando operations, but they carry risks.

The operation by about two dozen helicopter-borne special operations troops in north-western Syria - plotted for months, executed on a moonless night and monitored on video screens from the White House Situation Room - bore striking similarities to the US raids that killed Osama bin Laden in Pakistan in 2011, and the former ISIS leader, Abu Bakr al-Baghdadi, in the same part of Syria in 2019.

But because of the extensive planning and risks to troops that they entail, such raids are reserved for the most important targets.

US officials said they took care to avoid civilian casualties, evacuating 10 children from the building during the raid. That explosion appears to have been responsible for at least some of the 13 deaths in the operation, officials said.

But in complex raids, the military's initial version of events may be incomplete. Accounts of past operations have at times turned out to be contradictory or wrong, and the Pentagon said it was still collecting information from the raid.

3. Chaos in Syria offers militants a haven

President Bashar Assad has held on to power despite a decade-long civil war, but the Syrian state is a mess, with pockets of the country beyond his control and an illegal drug empire flourishing in government-held areas. A New York Times investigation last year found that Syrian elites with ties to Mr Assad are behind a multibillion-dollar industry trafficking an illicit amphetamine that has become the country's most valuable export, far surpassing its legal products.

The raid on Thursday took place in the Atmeh area, a rural backwater and smuggling town in the north-west that has swelled in population during the war. As tens of thousands of Syrians were displaced, huge camps sprang up, and analysts say militants have often hidden among civilians struggling to survive.

Atmeh is in Idlib province, which remains home to many violent extremist groups, dominated by Hayat Tahrir al-Sham, formerly the Nusra Front, which was previously linked to Al-Qaeda.

Another security vacuum exists in north-eastern Syria, where hardliners have found refuge by evading Kurdish-led militias supported by the US near the border with Turkey and in the desert that spans the border with Iraq.

Days before the raid, US forces backed a Kurdish-led militia in the city of Hassakeh as it fought for more than a week to oust ISIS fighters from a prison they had occupied. The battle killed hundreds of people and offered a reminder of the group's ability to sow chaotic violence.

4. It was a victory for Biden amid other crises abroad

As he confronts Russia over its military build-up on the borders with Ukraine and faces a deepening rivalry with China - as well as domestic challenges including rising inflation and an intransigent Republican opposition in Congress - US President Joe Biden secured a political victory with the mission in Syria. It eliminated one of the world's most wanted terrorist leaders with no loss of American life, according to US officials.

After Afghanistan fell to the Taliban, critics of Mr Biden said that his military withdrawal from the country would hamper intelligence gathering against terrorist networks. The hunt for Quraishi, whom intelligence officials had been tracking since last year, offered evidence that the US retained the ability to track militant leaders in Syria.

White House aides said that top Pentagon officials and military commanders apprised Mr Biden of their planning, at one point presenting a tabletop model of the building where the ISIS leader and his family lived - and noting that a Syrian family with no apparent connection to the terrorist group was living on the first floor.

Mindful of the high risk of harm to civilians and to the commandos, military engineers told Mr Biden that they did not believe the entire building would collapse if Quraishi detonated a suicide vest or other explosives on the third floor, according to an account from two Biden administration officials.

In the end, Mr Biden said, Quraishi died when he exploded a bomb that killed him as well as members of his own family.

The death of Quraishi allows Mr Biden, like his predecessors in the Oval Office, to claim credit for eliminating a militant leader whose group is responsible for numerous civilian deaths in Syria and Iraq, and for deadly terrorist attacks around the world.

5. ISIS will probably persist, even without a unifying leader

At the height of its powers around 2015, ISIS controlled a portion of Syria and Iraq that was about the size of Britain. It lured droves of foreign fighters from as far away as China and Australia, and ran a sophisticated propaganda machine that inspired or directed foreign attacks from Berlin to San Bernardino, California. By December 2017, after a sustained US-led military campaign, it had lost 95 per cent of its territory.

The fight continued as a US-led coalition joined with local forces in Syria and Iraq to roll back the group's gains. A Kurdish-led militia, the Syrian Democratic Forces, with US military support, pushed it from its last patch of territory in north-east Syria in early 2019. In October that year, the US raid killed the group's leader, Baghdadi.

After Quraishi replaced Baghdadi, the US put a bounty of up to US$10 million (S$13.5 million) on his head. Quraishi kept a low profile to evade capture, which analysts said prevented him from expanding the group's reach.

But the group has evolved to the point that one man's death does not mean it is no longer a threat.

"I don't think anyone should be under the illusion that removing him from the organisation is a death blow to Islamic State," said Mr Daniel Milton, director of research at West Point's Combating Terrorism Centre.

"This hopefully will hamper the organisation, but I don't think it will eliminate the threat in the future."