When Syria’s civil war erupted, Iran’s powerful Islamic Revolutionary Guards Corps (IRGC) recruited, trained, and deployed thousands of Shi’ite fighters to prop up the regime of President Bashar al-Assad. Among them was the Fatemiyoun Brigade, comprised mainly of Afghans from the country's Shi'ite Hazara minority. From 2011, the IRGC recruited thousands of Afghan migrants and refugees within its own borders and covertly drafted hundreds of Shi'a inside Afghanistan. The majority of Muslims in Afghanistan are Sunni, but around 15 percent of its population -- mainly Hazara -- are Shi’a with religious links to the Shi'ite majority in Iran. With the...