The seizure of all of Aleppo by Mr. Assad and his allies signals a turning point in the nearly six-year conflict.
Mr. Assad’s army relied heavily on foreign military support from Russia, Iran and Shiite militias like Lebanon’s Hezbollah to surround the rebel-held area. Months of shelling and airstrikes that killed hundreds of people and reduced entire neighborhoods to rubble finally routed the rebels and pushed the area’s inhabitants to leave under an agreement brokered by Russia, Turkey and Iran.
Throughout the conflict, Mr. Assad has characterized the rebels seeking his ouster as foreign-backed terrorists, and he hailed the retaking of Aleppo on Thursday as a blow to those forces. He also thanked the international backers who helped.
“Liberating Aleppo from terrorism is a victory not only for Syria, but also for those who really contributed to the fight against terrorism, especially Iran and Russia,” Mr. Assad said at a meeting with a visiting Iranian delegation, according to the Syrian state news service, SANA.
Many in the government-held western part of Aleppo also celebrated the routing of the city’s rebels, who often fired improvised rockets at their neighborhoods, flooding hospitals with the dead and wounded. And as hundreds gathered on Tuesday to see the lighting of a Christmas tree, a bomb exploded in western Aleppo, wounding no one but sending residents fleeing.
The evacuation was bitter for residents of the other half of the city, both rebel fighters seeking to topple Mr. Assad and the civilians who left their homes, unsure of when — if ever — they would return.
Residents reached by phone and messaging apps after arriving in rebel-held areas described cold, disorderly conditions where many were struggling to find shelter.
“People went from one hell to another,” said Abdul-Nasser Nadaf, a rebel fighter who had left eastern Aleppo for Idlib Province. “We are all tired, and the displacement was really tough. The snow and cold made things worse.”
Many people there had left their belongings behind and had arrived with no money, he said.
The ordeal had changed his thinking about the rebel movement, and he criticized its commanders for the infighting that had long sapped their movement and for the Islamist agenda that some had adopted.
“I might stop fighting. I lost the motivation,” Mr. Nadaf said. “The goals changed — the situation on the ground changed.”
Under the agreement, civilians removed from eastern Aleppo could remain in government-controlled areas or continue on to rebel-held areas elsewhere. Most have ended up in Idlib, which already held many people displaced from elsewhere in Syria, raising concerns about the humanitarian situation there.
The evacuated fighters were allowed to keep light arms and had to go to other rebel-held areas.
Aid workers fear that because of the concentration of rebel fighters in Idlib, it is only a matter of time before the government and its allies attack there, endangering civilians.
Almost all of the province is held by rebel groups, including the Syrian affiliate of Al Qaeda and other extreme Islamist groups.
Staffan de Mistura, the United Nations envoy to Syria, said on Thursday that only a deal to end the war could prevent a repeat of the carnage in Aleppo and protect the displaced.
“Many of them have gone to Idlib, which could be in theory the next Aleppo,” Mr. de Mistura told reporters in Geneva.
But the prospect of such a deal remained unclear.
While the victory in Aleppo will bolster the morale of Mr. Assad’s troops, he is widely seen as lacking enough military capacity to both hold his ground and seize other territory held by rebels and by the jihadists of the Islamic State.
This week, Russia and Iran, which support Mr. Assad, and Turkey, which has supported the rebels, met in Moscow and agreed to a framework for ending the conflict. Officials from the United States, the United Nations and the Syrian government were not included in the talks.
For his part, Mr. de Mistura has announced a new round of United Nations-backed peace talks in Geneva in February.