This was clearly some sort of loyalty test. Abu Ali felt their eyes on him, and he began to shake. He had been taught as a child that burning a man to death was forbidden in Islam. The images had sickened him. He heard himself say, 'May God help me.'

Two Isis guards took him by the arms and led him out of the cave. The emir followed later. He sat down on the rocks with Abu Ali and asked him why he had spoken those words. Did he question what Isis had done? Abu Ali said no. He had only spoken out because people were provoking him.

The emir seemed satisfied. 'At the beginning of this course you were a kafir (an unbeliever),' he said. 'Now you are becoming a Muslim.'

Abu Ali was intensely relieved. He had escaped punishment. But from that moment on, he told me, 'I began to suspect everything around me.'

He had joined Isis in the hopes of getting a desk job and making himself into a good Muslim.

In his previous life he had frequented bars and clubs and partied several nights a week, despite his wife’s constant haranguing. She was infertile, and the absence of children made their days especially empty.

By 2012 his father’s government work had stopped after the rebel Free Syrian Army entered Aleppo and his profligate life began tilting towards despair.

He was living off handouts from other family members abroad. Abu Ali declared that he was divorcing his wife. In Islamic law, that’s all it takes. She moved out.

After that, Abu Ali felt he had nothing left to lose. 

Reluctant figher: Abu Ali was transferred to the Garma district of Anbar province, west of the Iraqi capital Baghdad, where he was ordered to act as a medic, rescuing desperately wounded fighters

Battle scarred: Abu Ali refused to fight further because he was convinced the battle could not be won. He told his commander: 'We don't want to fight any more. You are leaving dead and wounded men behind. The prophet Muhammad, peace be upon him, did not force men to fight against their will'