BEIRUT: The Syrian regime has sent thousands of reinforcements to Aleppo, after suffering one of its most significant setbacks in the five-year war.
Rebel forces made a breakthrough at the weekend, relieving the siege on the east of the city, where up to 300,000 residents were at risk of starvation.
A 10,000-strong alliance of opposition fighters led by the formerly al-Qaeda-aligned Jabhat Fateh al-Sham took the beleaguered Syrian army by surprise on Saturday. They managed to sever the primary government supply corridor running into the city from the south and capture a military academy in the strategic district of Ramuseh.
Jabhat Fateh al-Sham posted pictures on social media of rows of armoured vehicles, munitions, howitzer tanks, rockets and trucks now in rebel hands. Since their defeat, Syrian and Russian warplanes have been pounding the area mercilessly.
"We are in our trenches, but there are insane air strikes of unprecedented ferociousness," a rebel commander said. "The regime is using cluster and vacuum bombs," he added. So-called vacuum bombs burn up surrounding oxygen and produce a cloud of explosives that can reach further and for longer than other weapons.
Some 2,000 pro-government fighters from Syria, Iraq, Iran and the Lebanese Shia movement, Hizbollah, arrived in the southern suburbs of Aleppo yesterday (Monday) to try to retake Ramuseh.
A defeat for the regime in Aleppo would see President Assad lose control of the entire north of the country, while a victory would tip the balance of power in his favour and strengthen his bargaining position at future peace talks.
The rebels' hold of the area is tentative and the road out remains too dangerous for civilians to use. If consolidated, however, the rebel gains could change the landscape of the conflict.
In a statement, the fighters, grouped under the banner of the Army of Conquest, announced "the start of a new phase to liberate all of Aleppo", pledging "double the number of fighters for this next battle." A spokesman for Jabhat Fateh al-Sham said he was confident they could hold back Mr Assad's forces: "The coming days should see an established, safe route that civilians can use," he said.
The group, formerly known as Jabhat al-Nusra, last month distanced itself from parent organisation al-Qaeda in a move intended to bring it closer to other rebels. "The world abandoned Aleppo; the jihadis came to the rescue. Al-Qaeda's rebranding could hardly have asked for more," said Kyle Orton, of the Henry Jackson Society think tank.
In retaliation for their losses, Russian jets on Sunday night dropped incendiary thermite bombs on a civilian area of the northwestern city of Idlib, according to emergency workers.
Videos reportedly taken by residents show whole buildings burning white, while children can be heard screaming. The use of air-dropped incendiary bombs on civilians would be a violation of the 1980 UN Convention on Certain Conventional Weapons.