A US soldier stands guard at the site of a suicide attack in the Afghan capital Kabul on September 16, 2014. A Taliban suicide bomber rammed an explosives-laden car into a NATO convoy close to the US embassy in Kabul on September 16, killing three soldiers and wounding at least 13 Afghan civilians. At the side of the road, US and Polish troops gave first-aid to blood-stained comrades beside the wrecked remains of a military vehicle, but the nationality of the dead soldiers was not confirmed. AFP PHOTO/Wakil Kohsar (Photo credit should read WAKIL KOHSAR/AFP/Getty Images)
ARLINGTON, VA - DECEMBER 14: (AFP OUT) U.S. President Barack Obama (C) delivers a statement on the counter-ISIL campaign in the Pentagon briefing room December 14, 2015 in Arlington, Virginia. President Obama met previously with a National Security Council on the counter-ISIL campaign. (Photo by Olivier Douliery-Pool/Getty Images)
WASHINGTON, DC - DECEMBER 01: House Armed Services Committee Chairman Mac Thornberry (R-TX) (C) delivers opening remarks during a hearing in the Rayburn House Office Building on Capitol Hill December 1, 2015 in Washington, DC. Defense Secretary Ashton Carter and Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford Jr. testified before the committee about the U.S. strategy to combat the self-proclaimed Islamic State, or ISIS, in Syria and Iraq and its implications for the greater Middle East. (Photo by Chip Somodevilla/Getty Images)
WASHINGTON, DC - DECEMBER 09: U.S. Defense Secretary Ashton Carter testifies during a hearing before the Senate Armed Services Committee December 9, 2015 on Capitol Hill in Washington, DC. The committee held a hearing on the U.S. strategy to counter the Islamic State of Iraq and the Levant and U.S. policy toward Iraq and Syria. (Photo by Alex Wong/Getty Images)
