Mohammed al-Hussain was driven to see his commander in the back of a nondescript saloon car, a twelve-year-old Toyota with darkened windows. The commander was based in a compound on the outskirts of Palmyra, pretty much in the middle of Syria. Palmyra had been gutted by the fierce fighting between the Syrian government and Islamic State fighters. The city’s historic Roman theatre had been left virtually untouched and was now used as a place of execution, the victims usually forced to wear orange jumpsuits before they were decapitated, often by children.

The commander was Azmar al-Lihaib, an Iraqi who had been one of the first to join Islamic State. His unit worked independently, often choosing its own targets, though special requests were regularly handed down from the IS High Command.

Al-Hussain was dog-tired. He hadn’t slept for more than thirty-six hours. The khat leaves he was chewing went some way to keeping him awake but his eyelids kept closing as he rested his head against the window. He must have dozed for a while because the car lurched to a halt unexpectedly causing him to jerk upright, putting his hands up defensively. They had arrived at al-Lihaib’s compound. The men in the unit never wore uniforms and the Toyota’s occupants were checked by two men in flowing gowns, holding Kalashnikovs, with ammunition belts strung across their chests.

They drove through the gates and parked next to a disused fountain. Al-Hussain climbed out and pulled the backpack after him. He never went anywhere without his rifle and even slept with it by his side. He spat out what was left of the khat, and green phlegm splattered across the dusty ground.

Two more guards stood at either side of an arched doorway and moved aside to allow him through. He walked down a gloomy corridor, his sandals scuffing along the stone floor. There was a pair of double wooden doors at the far end with another two guards. One knocked and opened them as al-Hussain approached. He hesitated for a second before he went through.

It was a large room with thick rugs on the floor and heavy purple curtains covering the window. Commander al-Lihaib was sitting cross-legged beside an octagonal wooden table inlaid with mother-of-pearl on which stood a long-spouted brass teapot and two small brass cups. Even when he was sitting down it was obvious that al-Lihaib was a big man and tall, while his Kalashnikov, on a cushion beside him, looked like a toy against his shovel-sized hands. He was in his forties with hooded eyes and cheeks flecked with black scars that looked more like a skin condition than old wounds. Like many Islamic fighters his beard was long and straggly, and the backs of his hands were matted with hair. His fingernails were yellowed and gnarled and his teeth were chipped and greying. He waved al-Hussain to the other side of the table, then poured tea into the cups as the younger man sat and crossed his legs.