On Sunday, as the militants of the Islamic State rolled west from Mosul toward the city of Sinjar, the ancestral home of the Yazidi people, thousands of members of the ancient, persecuted religious community fled their homes carrying whatever they could, to take shelter in the mountains. As many as 40,000 Yazidis -- of the estimated 130,000 who escaped -- are now trapped on Mount Sinjar, where they sought refuge. With food and water supplies running low, they will not be able to sustain their position for long; but should they descend, death or forced conversion await. Attendants of an 11th-century religion that combines elements of Zoroastrianism, Islam, and Christianity, the Kurdish-speaking Yazidis have been targeted by the Islamic State for extermination. As the Guardian reports, local officials estimate that 500 Yazidis "including 40 children, have been killed in the past week." On Thursday, the Obama administration authorized emergency humanitarian aid (the U.S. military dropped 5,300 gallons of fresh drinking water and food rations) as well as possible airstrikes to break the surrounding siege. The fighters of the Islamic State, Obama said, "have called for the systematic destruction of the entire Yazidi people, which would constitute genocide." In their history, the Yazidis claim that they have survived 72 attempts to wipe them from the earth. Their religion, which calls for the worship of a fallen angel, has historically made them a target of persecution. Now, with the world watching, they face one more. Above, members of an Iraqi Yazidi family that fled the violence in the northern Iraqi town of Sinjar sit together in the school where they are taking shelter in Dohuk, on Aug. 5. SAFIN HAMED/AFP/Getty Images