AL-HOL, Syria—The crack of a gunshot scattered a group of women throwing stones at a surveillance camera watching over the camp where they have been held with their children since the fall of Islamic State’s would-be caliphate.

As the internment of these non-Syrian adherents of the terror group drags on, desperation is swelling in the al-Hol camp, raising tensions between them and those left to guard this bleak assemblage of sagging tents surrounded by a chain-link fence.

Nine months since Islamic State’s experiment collapsed, thousands of children remain trapped here and in several other camps in northeast Syria—victims of geopolitics and hostage to the fortunes of their parents.

Only a fraction have made it out, including seven Swedish orphans whose grandfather, Patricio Galvez, traveled here in April and found them malnourished and traumatized. His journey helped pressure the Swedish government into taking them home.

Since then, a number of other countries—notably Kazakhstan and Kosovo—have moved to repatriate a total of around 350 children from Syria in 2019, according to Save the Children.