Turkey has invaded Kurdish-controlled territory in Syria, upending a fragile peace in the region and inciting sectarian bloodshed. The Trump administration has ordered a full evacuation of the 1,000 American troops that remain in northeastern Syria, leaving Gen. Mazloum Kobani Abdi and his Kurdish forces to rely on Russia and Syria for military assistance.   Who are the Kurds? How is it that Kurdish fighters came to be seen as allies to the United States and terrorists to Turkey? And what would the fall of Kurdish territory in northeastern Syria mean for the region? Guest: Ben Hubbard, Beirut bureau chief for The New York Times. For more information on today’s episode, visit nytimes.com/thedaily.  Background coverage: Turkey’s invasion upended a fragile peace and risks enabling the resurgence of the Islamic State.American troops who fought alongside Kurdish allies have expressed regret after the U.S. abandoned posts in northeastern Syria. “It’s a stain on the American conscience,” one Army officer said.