BEIRUT (AP) — In the sprawling al-Hol camp in northeastern Syria, Islamic State wives and widows have set up special courts, stabbed to death at least two people accused of apostasy and wielded knives and pistols in clashes with their Kurdish guards.

Now, as Turkish troops invade northern Syria and the U.S. abandons its Kurdish allies, there are renewed fears of a prison break in the camp that could give new life to the extremist group.

The Kurdish-led Syrian Democratic Forces, who captured much of northeastern Syria from IS with close U.S. military support, are mobilizing to stop the Turkish...