On a Friday afternoon in the fall of 2017, a few months after the liberation of Mosul from the Islamic State, a group of neighbors gathered at Mar Mattai, a monastery founded in the fourth century. They unloaded baskets of food, and arranged themselves around a long table in a courtyard. A woman named Niser spread out a tablecloth and put down a plate of dolmas. “It’s a way of celebrating that we still exist,” she told me. More people were arriving—children, grandparents, cousins, aunts, and distant relations—members of one of the oldest Christian communities in the world who had not seen one another for three years.