A still image captured from US Navy video shows US Navy Ordnancemen aboard the aircraft carrier USS George HW Bush building GBU-54 500-pound bombs in the Arabian Gulf on August 9 in this video released on August 11.  A series of U.S. airstrikes since last week has slowed the operational tempo of the Islamic State, the militant group that has seized large parts of northern Iraq, but is unlikely to substantially weaken the group, the Pentagon said on Monday.  Reuters/Preston Paglinawan/U.S. Navy/Handout via Reuters