Armed with new anti-tank missiles and, according to one rebel, higher-end weapons from Saudi Arabia and Qatar, the opposition has launched counter-attacks in the city's northeast and west.
"We advanced on the agricultural research centre," said Mohammed Abdullah, 35, a fighter on one front in Bustan al-Basha, eastern Aleppo.
The attack stalled when fighters were surrounded in a church and forced to retreat.
The operation is being called "The Battle of Qadisiyah", after a 7th century battle in which the Arabs defeated the Persian empire, in reference to the Iranian advisers helping Assad.
"We are starting to attack the Government," said Colonel Abduljabar al-Oqaidi, a former regime colonel who leads the Aleppo military council.
"The regime pushed forward in the north of the city, but the Free Syrian Army caused a lot of casualties and they went back to their bases."
The defeat at Qusair was the heaviest for the rebels since they were forced to withdraw from Baba al-Amr, the besieged district of Homs, in February last year. It prompted United States President Barack Obama to promise military assistance to the opposition. It also showed the rebels' shortcomings in planning and co-ordination.
Just before the southern city fell, Colonel Oqaidi and Abdulqader al-Saleh, the charismatic head of the Tawhid Brigade and one of the revolution's most celebrated fighters, led a rescue mission.
According to interviews with the Daily Telegraph and accounts since made public, it has emerged the mission came close to a fiasco, nearly killing both leaders, which would have been a devastating blow to rebel morale.
State media at one stage said troops had killed Saleh, though that was later withdrawn, and both men are now back in Aleppo to marshal its defences.
The first casualties came when the convoy of rebels, with Saleh at its head, hit a regime minefield, destroying three vehicles and killing nine men. By that stage, it was clear that the regime bombardment of Qusair was like nothing the rebels had previously seen.
"My son rang me half an hour before he died and asked me for my forgiveness and to pray for his martyrdom," said Atta Akrama, the father of one of the nine, Ziad, 27. "He said the shelling of the town was really bad."
Oqaidi added: "The firepower was overwhelming. I never saw such a thing in my life."
When the column finally made it into town, they discovered the rebels inside were already planning to withdraw, an example of the lack of co-ordination that has bedevilled the opposition's many different brigades.
"A few of the commanders did not have the will to fight any more," Oqaidi said. "They had lost morale."
The defenders agreed to stay on, and the two groups resisted for five more days, but then agreed there was no option but retreat. They took with them thousands of casualties and civilians.
Videos, confirmed by accounts of participants now in Lebanon and in Aleppo, showed streams of dejected people, mainly men but some women and children, staggering through fields and orchards. They came under repeated attack before breaking into separate groups. The Aleppo convoy had to break through regime lines under shellfire.
Oqaidi said the battle for Aleppo, if it came, would be nothing like that for Qusair. Aleppo is a major conurbation, with rebel forces well entrenched. It lies in the rebels' Sunni heartlands, while Turkey, the rebels' ally and one of the main conduits for their arms, is just 40km away. Qusair lies close to Lebanon, the home of Hizbollah.
Weapons supplies and unity among the rebel groups remains key. Abdullah, a Bustan al-Basha fighter, said the shortage of weapons meant they could make little headway against more than 4000 regime troops. The front line there has barely moved in six months.
Oqaidi has resigned from the Revolutionary Military Council, headed by General Selim Idriss, complaining that weapons supplies are still being sent to brigades favoured by donors such as Qatar and Saudi Arabia, rather than through a central command structure.
"Some new weapons have been supplied to different brigades," he said, referring to reports that new anti-tank missiles and even some anti-aircraft missiles had been provided.
"But Saudi and Qatar are still favouring their own groups."
He said the most important lesson of Qusair was now being put into practice - that it was pointless to wait for the enemy to come to you. "Attack is the best form of defence."
