President Bashar al-Assad had kept opposition forces at bay for a decade with help from Russia and Iran. But rebels struck at a moment of weakness for those countries.
The government of President Bashar al-Assad of Syria, which had kept rebel forces at bay for more than a decade with Iranian and Russian military support, collapsed with astonishing speed on Sunday morning after an advance by opposition forces on the capital, Damascus.
Mr. al-Assad fled the country as rebel forces closed in on Damascus, according to the Russian government, one of his main allies. The whereabouts of Mr. al-Assad, an authoritarian leader who had gassed his own people during a 13-year civil war, were unclear early on Sunday.
The rebel offensive had lasted less than two weeks.
The Russian foreign ministry said Mr. al-Assad had “decided to leave the presidential post and depart the country” after talks with other “parties to the conflict.” He had given instructions to transfer power peacefully, the ministry said.
There was no comment from Mr. al-Assad. His former prime minister, Mohammad Ghazi al-Jalali, stayed behind and said he was ready to cooperate with the rebels. The opposition forces swept into Damascus with little apparent resistance from the Syrian military, seizing control of government buildings and the state broadcaster.
For years, the Syrian civil war — which had erupted in tandem with the anti-government Arab Spring uprisings in 2011 and continued with horrific violence until 2017 — remained unresolved, but relatively stagnant.
Then, in October 2023, Hamas attacked Israel, and the subsequent war upended the regional chess board of the Middle East. The Syrian rebels struck at a moment of weakness for Mr. al-Assad’s main allies: Iran, Russia and Hezbollah, the militant group based in Lebanon and backed by Iran.
Iran’s power has been curtailed by its conflict with Israel. Hezbollah, Iran’s main proxy force in the region, whose fighters had also played a key role in propping up Mr. al-Assad, has been battered by the war with Israel as well, with its top leaders killed. In Europe, the invasion of Ukraine has sapped Russia’s military of men, munitions and other resources.
Waiting in the wings was Hayat Tahrir al-Sham, or the Organization for the Liberation of the Levant, an Islamist group once linked to Al Qaeda. It later joined a coalition with more moderate partners but is still classified as a terrorist organization by the United States and others. In recent years, the group maintained its authoritarian rule over Idlib Province in the northwest for half a decade, taxing residents to run its operations but following Islamic precepts to respect minority groups.
About a year ago, it began preparing for a sweeping offensive south toward Damascus. The coalition, which analysts said received covert support from Turkey, established a military training academy in the north, churning out disciplined, highly motivated officers and soldiers, the analysts said.
“The revolution has transitioned from chaos and randomness to a state of order,” Abu Mohammed al-Jolani, the commander of the rebel units, said last week in a television interview.
Mr. al-Jolani’s coalition launched its lightning offensive on Nov. 27, first taking Syria’s largest city, Aleppo. The rebels went on to seize the city of Hama, which had never fallen during the civil war, and then Homs, a strategic city about 100 miles from the capital.
Another group of insurgents from south of Damascus were actually the first to enter the capital. At times the rebels seemed as surprised by their success as the rest of the world.
On the other side, Syrian government forces had done little to rejuvenate themselves. “They had low morale, no training, no weapons, no chain of command and a lot of corruption,” said Ibrahim Hamidi, the Syrian editor in chief of Al Majalla, an online current events magazine based in London.
Syrian government forces, without troops from Hezbollah and Iran to back them and with relatively little support from Russian airstrikes, collapsed in disarray. Even the Fourth Armored Division and the Republican Guards, the elite forces stationed around Damascus to in theory make it coup-proof, seemed to evaporate.
“We have seen the hollowing out of the Syrian state,” said Mona Yacoubian, head of the Middle East and North Africa Center at the U.S. Institute of Peace in Washington.
President Vladimir V. Putin of Russia had built his strategy of making Moscow a player again in the Middle East around his support for Mr. al-Assad, even as the Kremlin grew weary of his refusal to engage with Turkey, not to mention the opposition, to settle the conflict. “It is a humiliation for Putin,” Mr. Hamidi said.
Amid the many conflicts of the Middle East, the United States had long had an ambivalent relationship toward the situation in Syria, wary of pushing for a regime change that would bring what Obama administration officials used to call the “catastrophic success” of a jihadist government in Damascus.
There are about 900 American soldiers in Syria, deployed in the northeast to back up a Kurdish militia there that had fought against the Islamic State militant group. President-elect Trump had moved to withdraw them during his previous presidency, describing the country as “death and sand.” Now president-elect, he has repeated that the U.S. should not get involved in Syria now.
It is not clear what kind of government will emerge in Syria, given the disparate coalition that brought down Mr. al-Assad, whose father first took over in a coup in 1970.
Whatever the outcome, said Robert S. Ford, the American ambassador to Syria from 2011 to 2014, it is imperative for Washington “to decide once and for all what is their primary objective in Syria.”
Other governments with stakes in the outcome in Syria will no doubt also be recalibrating, as will groups like the Islamic State, which once established a Caliphate in eastern Syria and has been resurgent in that desert region in recent months.
For now, Syrians who opposed Mr. al-Assad were ecstatic. In what were long rebel-held areas, people delighted in finally being able to look at the sky without fear of bombs raining down on them. And residents of Damascus who lived through years of his oppressive rule, expressed relief, but remained wary.
Walaa Salameh, a mother of two young children, said she felt she was experiencing freedom for the first time in her life. But she added that she knows uncertainly lies ahead as the policies of a new government become clear.
“Hopefully what is coming is better,” she said.
Alan Yuhas contributed reporting.
Neil MacFarquhar has been a Times reporter since 1995, writing about a range of topics from war to politics to the arts, both internationally and in the United States. More about Neil MacFarquhar