Just over a month into Syria’s uprising in 2011, the leader of Lebanon’s Druze sect, Walid Jumblatt, travelled to Damascus to visit Syria’s then security tsar, Mohammed Nasif. As well as being the Assad family’s most trusted senior official, he was also the linchpin of Syria’s close ties with Iran and Hezbollah, a man bound more than most to the fate of the regime.

“He said to me at the time, it’s either us, meaning the Alawites, or them, meaning the Sunnis,” Jumblatt recalled. “I knew which way this was going then. He added, ‘even if it cost us a million dead’.”

More than five years later, the toll in the now raging war is well past a quarter of that estimate – international monitors stopped counting last August. The sectarian dimension to the fighting foreshadowed by Nasif is a reality. So is the destruction of much of the country, including the ancient city of Aleppo, which after years of being viewed as the key to Syria’s fate last week slipped from the grasp of the opposition and into the hands of the Syrian regime’s allies, led by Hezbollah.

The encirclement of Aleppo is a significant moment in a war that has led to more unrestrained savagery, international repercussions and unlikely alliances than most others in modern times. Another emerged last week, as Hezbollah and Syrian troops were beating back the al-Qaida-aligned Jabhat al-Nusra from farmlands to the north of the city. As that battle raged, the US was drafting a deal with Russia that would create a joint operations centre to coordinate attacks on al-Nusra and Islamic State.

The move has created despair among the ranks of the Syrian opposition, which insists that a pact between Moscow and Washington will entrench the Syrian leader, whom Russia and Iran have saved from defeat over the past 12 months. Adding to the alarm of the now diminished rebel ranks is a detente, also signed during the week, between Moscow and Ankara, after a seven-month standoff, as well as the Turkish prime minister’s remarks that Ankara was interested in peace with Damascus.

“This all means that Assad is no longer at risk,” said a senior official in the western-backed Syrian opposition. “This means that he has won.”

A civil defence member looks for survivors amid rubble of damaged houses after an airstrike on rebel-held Old Aleppo. Photograph: Abdalrhman Ismail/Reuters

In the eyes of the exiled political opposition and rebel fighting groups still in Syria, the political realignments mark a decisive phase in a war that they believe they can no longer win. In recent years, as Bashar al-Assad’s allies have weakened the rebels’ position, a belief endured among opposition military leaders that if they could not win the war, Assad could not either. That view has changed.

“I’m sitting here in a ruined house in eastern Aleppo,” said Abu Sobhi Jumail, a Syrian opposition fighter who has fought across northern Syria for the past five years. “I have the Russians in the skies, the Syrian air force too, when its planes can fly. I have Isis to my east, Hezbollah to my north and al-Qaida [Jabhat al-Nusra] in between. They abandon us, and tell us to rely on God, and then condemn us when we are forced to seek help [from al-Nusra]. Without them we would all have been killed a year ago. That is not politics. That is life and death.”

Since Russia launched its large-scale intervention last October, opposition units that had been backed by Saudi Arabia, Turkey and the US have been the prime targets of Moscow’s bombers. Isis has largely been spared, with notable exceptions such as in Palmyra.

Turkey, too, has mostly left the jihadis alone, concentrating its fight on Syria’s Kurds, whom it views as a subversive extension of Turkish Kurdish groups, which Ankara continues to fight.

Though remaining a supporter of the Syrian opposition, including Islamic elements such as Ahrar al-Sham, President Recep Tayyip Erdoğan, has focused much of his energies on ensuring that Syria’s Kurds do not seize control of more of the shared border and that their use by the US as proxies in the fight to seize land from Isis in eastern Syria does not amplify the Kurds’ ambitions.

“We are doomed in Aleppo,” said Suleiman Aboud, who fled with his family from the rebel east of the city in February. “The next phase of this will be revenge. No one has paid a price for all these abuses. That is what hugging Assad does. This revolution was noble. It may not have been fully democratic, but people are allowed to fight oppression. We have the same rights to safety and freedom as you.”

Acknowledging the immense suffering across rebel-held parts of the country, Gareth Bayley, the UK’s special envoy for Syria, said: “The situation on the ground in Syria is dire. The UK is deeply concerned by the regime and its allies taking ground and harming civilians in Aleppo and rural Damascus. This is in direct violation of the cessation of hostilities and there is appalling suffering amongst the population.”

There is no way out of eastern Aleppo and north to the Turkish border, with the last remaining supply line severed. A blockade that has all but taken hold over the past year is now likely to be enforced, say the few remaining residents of the eastern half of the city.

“For a long time people have been out of ideas,” said Abu Subhi. “There is no enthusiasm to assist us. They want it all to go away. But you will all be judged for what has happened in Syria. I won’t be alive to witness it, though.”