When the terrorist group ISIS emerged in Syria in the last decade, some 30,000 foreign fighters went to Syria to fight for the group. Most were from Europe and Asia. About 300 Americans joined or attempted to join ISIS, including one woman who was married to an American ISIS fighter.
After brutal battling over Raqqa, challenges lie ahead for the alliance now holding the Syrian city: Kurdish and Arab fighters, backed by the US, have to rule over a Sunni Arab city that they destroyed, and a population that views them with suspicion.