Kurdish forces allied to the U.S.-led coalition in the fight against the Islamic State have committed war crimes by deliberately displacing thousands of civilians and demolishing their homes in northern Syria, according to a human rights group. In a report released Tuesday, Amnesty International said that the People's Protection Units (YPG)—the military wing of the Syrian Kurdish political party, the Democratic Union Party—had in some cases threatened residents with U.S. airstrikes if they did not leave their homes. The YPG has been a key ally on the ground for Western forces battling ISIS in Syria. Earlier this year, the YPG...