The warning came over the radio just as tanks rumbled into Prijedor in northwestern Bosnia on a gray April morning in 1992. All Muslim men and boys aged 12 and older were ordered to leave their homes and line up in the street. Enesa Krupi?’s mother, calling from another city, told her Serbian soldiers, following orders from then-president Slobodan Miloševi?, were moving block by block — tanks in front, troops behind and empty buses in between. The buses weren’t just for show. One by one, men and boys were being loaded into the buses and taken away from the town...