U.S. military commanders have been given the authority to target Islamic State fighters in Afghanistan, the Pentagon said on Thursday, the first such order beyond Iraq and Syria, where the militants control parts of both countries. The U.S. State Department said last week that it had designated Islamic State’s offshoot in Afghanistan, known as Islamic State-Khorasan, as a foreign terrorist organization. U.S. forces could previously strike Islamic State in Afghanistan but it was under more narrow circumstances, such as for protection of troops.