U.S. President Barack Obama authorized air strikes on Iraq to protect Christians and prevent "genocide" of tens of thousands of members of an ancient sect sheltering on a desert mountaintop from Islamic State fighters threatening to exterminate them. The United States began to drop relief supplies to refugees from the ancient Yazidi sect, but there was no sign yet of air strikes, which Obama authorized for the first time since pulling troops out in 2011. ... U.S. oil majors Exxon Mobil and Chevron evacuated expatriate staff from Iraqi Kurdistan on Thursday, industry sources said. Smaller oil companies that operate in...