Sakhidad Afghan was 19 when he started working as an interpreter for the U.S. military in Afghanistan, in 2009. His father was sick and he wanted to help support their extended family of 18. In his first year, he saw combat with the Marines in the Battle of Marjah, but he remained an interpreter until the fall of 2014, when American troops drew down and his job disappeared. By then he’d received an anonymous death threat over the phone, so he’d applied for a special visa to live in the United States. He’d been in the application pipeline for three...