The village had no name. Everyone who had known the name of the village was now dead or had fled. When the Kurdish peshmerga fighters had recaptured the settlement from ISIS that spring, it was so full of booby-traps that they just torched the place rather than deal with it. The town was abandoned now—just somewhere for the men to come scavenge.

“This one’s my house,” Christopher Smith grinned. The former Marine corporal gestured with his battered AK-47 toward a fire-gutted jungle-green villa. All the buildings were like that—vibrant non-sequiturs of blue, yellow, purple. “It’s like Super Mario World,” the 25-year-old remarked.

While thousands of Europeans and North Americans have joined ISIS, at least a hundred Westerners have enlisted as fighters against the terrorist group. Compelled by reports of the Islamic State’s gruesome activities, the first volunteers came in the fall of 2014. They have enrolled in a number of regional militias including the peshmerga—the government-backed army of Iraqi Kurdistan under which Smith currently serves.

The village we walked through was slowly turning back into desert—disappearing by the truckload as its wreckage went to fortify the Mullah Abdullah frontlines two kilometers away. The end of Kurdistan is marked by a dull earthen rampart studded with the bright dreamland fragments of the nameless village. Seven hundred meters beyond, across a minefield, is the Islamic State.

Two months before that day in December, Smith had been a brick mason living in Vermont with a fiancée. That was all over now. “I took the wrong bus to Miami,” he joked. In fact, the American had flown to Sulaymaniyah, Kurdistan, on a one-way ticket. With his military papers in hand, the veteran had walked into the Ministry of Peshmerga Affairs and enlisted.

While there is no specific U.S. law against fighting with a force like the peshmerga, the State Department has explicitly discouraged it. After he left, Smith said he called the FBI, notifying the agency of his whereabouts. “They knew I was here,” he insisted, “but they still felt the need to wake up my mother in the middle of the night and give her a heart attack.”

The American spoke of ISIS atrocities, the stories that had troubled his sleep back home: the beheadings and crucifixions, the slave markets, the rape camps—an evil that overwhelmed his senses. It was the reason he had come to fight, and like many of the volunteers I met, he was not here just to kill Daesh (a derogatory term for ISIS)—he was here to send Daesh to hell. The foreigners hunted wild boar to supplement their rice rations and made sure that every round fired in anger was coated in the animal’s unholy blood.

Hell is real here. The black inferno rages just beneath our feet, my translator warned. Everything is known from scripture. The flames have been measured, he insisted, and they are 69 times more painful than terrestrial flames.

There were always two wars going on—the one we could see, and the one we could not. Over 1,300 years ago, the prophet Muhammad spoke of the world’s final hour. The armies of Rome, he said, will be lured to the plains of Syria and annihilated. Only then will the Mahdi, the messiah, descend from heaven to defeat the cycloptic antichrist, Dajjal. Every phenomenon here is infused with mystical significance. ISIS distributes photographs of one-eyed babies, and the pesh commander at Makhmour, a hundred kilometers away, reports recurring nightmares of Kurdistan’s capital underwater—a city of corpses carried deep into the earth by an inescapable current.