When the Libyan arm of the Islamic State first raised the group’s black flag over the coastal city of Surt almost one year ago, it was just a bunch of local militants trying to look tough.

Today Surt is an actively managed colony of the central Islamic State, crowded with foreign fighters from around the region, according to residents, local militia leaders and hostages recently released from the city’s main prison.

“The entire Islamic State government there is from abroad — they are the ones who are calling the shots,” said Nuri al-Mangoush, the head of a trucking company based here in Misurata, about 65 miles west of the Islamic State’s territory around Surt. Many of its employees live in Surt, and five were jailed there recently…

“Libya is the affiliate that we’re most worried about,” Patrick Prior, the Defense Intelligence Agency’s top counterterrorism analyst, said at a recent security conference in Washington. “It’s the hub from which they project across all of North Africa.”