There may be little common ground among Syria's fractious opposition groups, but they have long agreed that the country's largest city, Aleppo, is vital to their plans to overthrow the government of President Bashar Assad.
With the city divided between the government and the opposition since 2012, its eastern neighborhoods emerged as the rebels' most important bastion, and a full takeover was to be the launchpad for a victorious march to the capital, Damascus, almost 200 miles to the southwest.
But Sunday, that scenario appeared more remote than ever, as pro-government troops expanded their hold on vital sections of eastern Aleppo, burrowing farther into the rebels' enclave even as thousands of civilians escaped into government-controlled areas to flee the violence, state media and opposition activists said.
A day earlier, the Syrian army announced that it had seized a key neighborhood on the outskirts of the city's eastern flank, 13 days into an all-out government offensive to finish off the rebels. The takeover carried symbolic weight - the neighborhood, the Hanano Housing district, was the first to fall to the rebels in 2012.
But it was also the beachhead from which government troops, on Sunday, were able to consolidate their control on the nearby neighborhood of Jabal Badro, according to SANA, the state news agency.
Pro-government activists on social media reported troops also breached three adjacent neighborhoods. Later on Sunday, SANA reported the army had established fire control over the Hellok and Sakhour districts, which lie on the front line separating rebel areas from government-controlled parts of western Aleppo. The move effectively split the rebel enclave in two, while a ferocious rocket barrage pummeled other opposition areas near the center of the city.
Even as troops advanced from the east, the Quds Brigade, a Palestinian paramilitary group fighting alongside the government in Aleppo, advanced on the besieged rebels' northeastern flank, according to the group's official account on social media.
Rami Abdul Rahman, head of the Syrian Observatory for Human Rights, a pro-opposition monitor based in Britain with a network of activists in Syria, acknowledged the government's progress.
In recent months, a large-scale campaign, backed by Russian air power and thousands of Shiite militiamen from Lebanon, Iraq, Iran and Afghanistan, established a punishing siege on the estimated 250,000 residents living in the rebel enclave. Despite several counteroffensives, the rebels failed to punch through government lines.
As the rebels retreated deeper into their enclave, thousands of civilians escaped to government-controlled areas through Hanano. State media said the armed forces had "secured the exit" of 1,500 people.
The Syrian Observatory for Human Rights put the number at 4,000, saying that an additional 6,000 had made their way to Sheikh Maqsoud, a northern Aleppo neighborhood controlled by a Kurdish militia, which has forged an uneasy alliance with the government in the area.
Syrian state television beamed images of uniformed fighters running through thoroughfares near an important mosque in Hanano, as well as video of ragged-looking civilians riding on buses provided by the government to shelter areas in western Aleppo.
In recent weeks, the government, along with its ally, Russia, had opened up humanitarian corridors for eastern Aleppo residents during unilaterally imposed cease-fires.
Rebels who laid down their arms were promised an amnesty allowing them to return to government areas. Those who refused could take their personal weapons and receive passage to join other rebels in the opposition-held province of Idlib, west of Aleppo.
In one bizarre initiative, the government even invited east Aleppo residents to a "friendly soccer game" as a way to build confidence.
Despite the government repeatedly exhorting the rebels through leaflets and phone messages to abandon their positions inside the city "before it was too late," very few heeded its call.
Instead, rebels shelled the checkpoints the government had set up to receive those who left. Meanwhile, the Syrian Observatory for Human Rights reported gunfire near the rebel side of the passageways, and said it had prevented roughly 100 families from leaving. It did not specify who had fired the weapons.
The government said the rebels had prevented civilians from escaping, and accused them of using residents as human shields.
On Nov. 19, the U.N. special envoy to Syria, Staffan de Mistura, proposed that the government stop its offensive after more hard-line Islamist elements inside the city leave their positions, while the opposition's administrative bodies continue managing the city. Damascus refused, effectively sidelining the U.N.'s political efforts in Aleppo, said regional expert Mouin Rabbani, a former member of the envoy's staff.
"I think it's fair to say that the U.N. under De Mistura's stewardship has been reduced to an incoherent spectator," Rabbani said in an interview from Amman on Sunday. "[It] has largely forsaken its political role and responsibilities to focus on humanitarian issues."
The speed of the opposition's fall in eastern Aleppo surprised pro-opposition activists, who accused the rebels on social media of betraying residents there. Commentators on Syrian television, meanwhile, exulted in what they said was an impending victory of the government.
Pro-government activists, meanwhile, quoted a statement from what they called a "security source" in the army's operations room in Aleppo.
"Whoever thinks for one moment that the army and its allies will renege on their goal to liberate all of Aleppo city is delusional," said the source.
"This is a final decision and there is no turning back from it."