The women say it was misguided religious faith, naivety, a search for something to believe in or youthful rebellion.
Whatever it was, it led them to travel across the world to join the Islamic State group.
Now after the fall of the last stronghold of the group's "caliphate," they say they regret it and want to come home.
The Associated Press interviewed four foreign women who joined the caliphate and are now among tens of thousands of IS family members, mostly women and children, crammed into squalid camps in northern Syria overseen by the U.S.-backed Kurdish-led forces who spearheaded the fight against the extremist group.
Many in the camps remain die-hard supporters of IS. Women in general were often active participants in IS's rule.
Some joined women's branches of the "Hisba," the religious police who brutally enforced the group's laws. Others helped recruit more foreigners. Freed Yazidi women have spoken of cruelties inflicted by female members of the group.
Within the fences of al-Hol camp, IS supporters have tried to recreate the caliphate as much as possible. Some women have re-formed the Hisba to keep camp residents in line, according to officers from the Kurdish-led Syrian Democratic Forces guarding the camp.
While the AP was there, women in all-covering black robes and veils known as niqab tried to intimidate anyone speaking to journalists; children threw stones at visitors, calling them "dogs" and "infidels."