Each year an estimated 300,000 smugglers, known as ‘kolbars,’ haul millions of pounds of contraband from Iraq to Iran over the 14,000-foot peaks of the Zagros Mountains. More than 50 of them will die—shot dead, killed in accidents, or freezing to death—and countless more will be arrested and imprisoned. Alex Perry travels to Iraqi Kurdistan to investigate the roots of a trade that all but defies comprehension.