SINJAR, Iraq — Khodeda Abbas is one of the saved. His wife went into labor coming off the mountain and needed medical assistance right away. The couple had just arrived at a shabby medical tent 20 kilometers from Mount Sinjar, along with hundreds of other refugees rescued in tractors, buses and cattle trucks. The drivers were all volunteers, men with enough gasoline and empathy to cross the desert and take exhausted strangers from Iraq into Syria over a border made only of dust. The tent had run out of medical supplies three days earlier.

It was here that Abbas smoked the best cigarette of his life, he said, after becoming a father to the sleeping baby in the milk crate by his feet. He named the child Farman. “It means ‘the tragedy,’” he said, “to remind him of where he came from.”

The tragedy in question began nine nights earlier, on Aug. 3. News of it arrived through the screams of the neighbor banging on Abbas’s door in the village of Siba Sheikh Khidr, on the outskirts of Sinjar town in northwestern Iraq: “Peshmerga have left. Daash are coming.” (Peshmerga are Kurdish security forces; Daash refers to the Islamic State, or IS — the armed Sunni fighters who are seeking to establish an independent state crossing the current borders of Iraq and Syria.)

In recent weeks, IS forces have advanced deeper into Syria and overtaken cities in northern Iraq, killing, imprisoning and evicting those who don’t submit to their cause. Kurdish forces in both countries have also been taking advantage of the current chaos to expand their territories. Here, the border between northwestern Iraq and northeastern Syria has effectively disappeared. Alliances are shifting and national identities are being discarded; many are turning to those they fear the least.