President Trump granted Defense Secretary Jim Mattis the authority to increase troop levels in Afghanistan this week, as the administration prepares a new strategy for the conflict there that has embroiled the United States for nearly 16 years. Mattis confirmed his new authority during a June 14 Senate Appropriations defense subcommittee hearing. He said the U.S. mission in Afghanistan remains the same -- to train, advise and assist Afghan forces -- as officials finalize a new strategy to present to...