SIRTE, Libya – One mild morning in October, when the roar of fighter jets over Sirte had died down and the crackle of gunfire had paused, Minya Mesmer decided to break free.

After 14 months as a slave in Libya, the 33-year-old Eritrean had to get away. She could no longer let her Islamic State captors rape, sell and exchange her or her 14-year-old daughter.

Her previous attempt to escape had left her with two broken legs. But she had healed enough to try again, she thought. She could lean on her daughter and limp past the cargo containers that marked the limits of Islamic State’s shrinking caliphate in the besieged city.

That morning, Mesmer (sounds like mess-mur) shared her plan with her daughter and another 16-year-old Eritrean girl. There were 22 other women holed up in the same building, all of them migrants enslaved by Islamic State. But Mesmer kept the others in the dark, worried that a large group would draw too much attention.