In this Aug. 10, 2014 photo, an aircraft for missions targeting the Islamic State group in Iraq lands at the USS George H.W. Bush in the Persian Gulf. Combined U.S.-Arab airstrikes at the heart of the Islamic State group's military strongholds in Syria achieved their strategic aim of showing the extremists that their savage attacks will not go unanswered, the top American military officer said Tuesday, Sept. 23, 2014. (AP Photo/Hasan Jamali)