U.S. Marines arrive at Saudi Arabia's Dhahran Air Base on Aug. 21, 1990. The U.S. began a buildup in the region just days after Iraq invaded Kuwait on Aug. 2 of that year. The U.S. military has been active in Iraq virtually nonstop for the past quarter-century. Gerard Fouet/AFP/Getty Images hide caption

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A Marine Corps F-35B Joint Strike Fighter does a short takeoff (STOVL) from Patuxent River Naval Air Station, Md., in 2011. Eighteen years after development began, a version of the plane designed for the Marine Corps is expected to be deemed "combat ready." Cliff Owen/AP hide caption

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The Japanese supercomputer K, pictured in June 2012 at the RIKEN Advanced Institute for Computational Science in Kobe, western Japan. The K computer is currently ranked No. 3 on a list of the 500 fastest supercomputers. Kyodo/Landov hide caption

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Secretary of State Hillary Clinton testifies in January 2013 before the Senate Foreign Relations Committee on the attack on the U.S. mission in Benghazi, Libya. Mandel Ngan/AFP/Getty Images hide caption

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Zachary Gallegos, 23, stands guard outside the Armed Services Recruiting Center on Thursday in Sioux Falls, South Dakota. The Pentagon has asked such self-appointed "armed citizens" to leave, citing security concerns. Kevin Burbach/AP hide caption

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