IRBIL, Iraq — A U.S. Marine was killed near the front line with the Islamic State in northern Iraq on Saturday, becoming the second combat casualty of the war against the militants, according to the U.S. military and Iraqi officials. The Marine died when Islamic State militants fired rockets into a small U.S. base in Makhmour, a front-line town controlled by Kurdish peshmerga forces on the outskirts of the region of Kurdistan, U.S. officials said. “Several” other Marines also were injured in the rocket attack, according to a Pentagon statement. An earlier statement had not specified which branch of the...