As the fight against the Islamic State in Syria (ISIS) draws to a bloody conclusion, the question of what will happen to the ISIS prisoners of war (POWs) who were captured by the U.S.-led international coalition or its local partners becomes increasingly pressing.

During a Senate Armed Services Committee hearing, General Raymond Thomas, the head of the U.S. Special Operations Command (SOCOM), said that the coalition and its partners have close to “a thousand already in detention, with more to potentially come.” General Thomas emphasized the danger that these POWs pose to American interests and the region’s stability.

The ISIS POWs aren’t detained by the Iraqi government, but rather by the Syrian Democratic Forces (SDF), a coalition of groups led by the Kurdish Peshmerga. During the hearing, General Thomas noted that the SDF is a non-state actor, inferring that the group operates outside the international system that guides modern warfare.

“How we reduce that threat and keep those people properly detained and handled over time is of paramount importance right now,” added General Thomas.