A visitor wearing stands beside an Al Sabr unmanned aerial vehicle (UAV) manufactured by Abu Dhabi Autonomous Systems Investements (ADASI) on display at the International Defence Exhibition (IDEX) in Abu Dhabi, United Arab Emirates, on Monday, Feb. 23, 2015. The threat of extremist groups will persist in the Middle East even if Islamic State militants are defeated, a U.S. defense official said. Photographer: Gabriela Maj/Bloomberg via Getty Images
