Guardian

If some of the foreign fighters in Aleppo were callow, others such as Abu Salam al Faluji boasted extraordinary experience. Abu Salam, a rugged Iraqi with a black keffiyeh wrapped around his head, said he had fought the Americans in Falluja when he was a young man. Later he joined al-Qaida in Iraq and spent many years fighting in different cities before moving to Syria to evade arrest. These days he was a commander of the one of the muhajiroun units.

I found him watching a heated debate between the Syrian commanders about how to defend the buckling frontline.

The government attack had begun as predicted and mortars were exploding in the streets nearby, the sound of machine-gun fire ricocheting between the buildings. The mortars were hammering hard against the walls, sending a small shower of shrapnel and cascading glass, but Abu Salam stood unflinching.One Syrian, breathing hard, said that he had fired three times at the tank and the RPG didn't go off.

"Don't say it didn't go off," Abu Salam admonished him. "Say you don't know how to fire it. We used to shoot these same RPGs at the Americans and destroy Abrams tanks. What's a T72 to an Abrams?

"Our work has to focus on IEDs and snipers," he told the gathering. "All these roofs need fighters on top and IEDs on the ground. You hunt them in the alleyways and then use machine-guns and RPGs around corners.

"The problem is not ammunition, it's experience," he told me out of earshot of the rebels. "If we were fighting Americans we would all have been killed by now. They would have killed us with their drone without even needing to send a tank.

"The rebels are brave but they don't even know the difference between a Kalashnikov bullet and a sniper bullet. That weakens the morale of the men.

"They have no leadership and no experience," he said. "Brave people attack, but the men in the lines behind them withdraw, leaving them exposed. It is chaos. This morning the Turkish brothers fought all night and at dawn they went to sleep leaving a line of Syrians behind to protect them. When they woke up the Syrians had left and the army snipers had moved in. Now it's too late. The army has entered the streets and will overrun us."

He seemed nonchalant about the prospect of defeat.

"It is obvious the Syrian army is winning this battle, but we don't tell [the rebels] this. We don't want to destroy their morale. We say we should hold here for as long as Allah will give us strength and maybe he will make one of these foreign powers come to help Syrians."

The irony was not lost on Abu Salam how the jihadis and the Americans – bitter enemies of the past decade – had found themselves fighting on the same side again.