Hareth Najem fled Islamic State's last enclave in eastern Syria wounded and alone. The Iraqi orphan's family had died two years earlier in airstrikes across the border in al-Qaim region.

"I had two brothers and a sister. They all died, and then I was by myself," Hareth said, tears filling his eyes. "My little sister, I loved her a lot. I used to take her with me to the market."

Lying in a cattle truck beside another injured boy at a desert transit point for U.S.-backed forces, he huddled under a blanket. His face was covered in dirt and the side of his head wrapped with bandages covering wounds incurred days earlier.