A row of Secure Housing Units at the Corcoran State Prison in California in 2013. The prison has a separate facility built for inmates held in solitary. Robert Galbraith/Reuters /Landov hide caption

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An International Atomic Energy Agency inspector cuts a uranium enrichment connection at Iran's Natanz facility, 200 miles south of Tehran, in 2014. The U.S. Congress is expected to address the Iranian nuclear deal this month. One unresolved issue: How much work might Iran have done previously on weaponizing its program? Kazem Ghane/AP hide caption

itoggle caption Kazem Ghane/AP

The Pentagon's only maximum security prison, at the U.S. Army's Fort Leavenworth in Kansas, is one of the facilities being considered for placement of Guantanamo prisoners deemed too dangerous to release. Julie Denesha/Getty Images hide caption

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French President Francois Hollande and U.S. Ambassador to France Jane D. Hartley stand with (from left) Alek Skarlatos, Spencer Stone and Anthony Sadler as they leave the Elysee Palace in Paris. The three American men, along with a British citizen, were pinned with Legion of Honor medals Monday morning for tackling a gunman on a train. Michel Euler/AP hide caption

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U.S. Air Force F-22 Raptors are seen parked at Kadena Air Base on the island of Okinawa in Japan. The U.S. military established a presence on Okinawa during World War II. Yoshikazu Tsuno/AFP/Getty Images hide caption

itoggle caption Yoshikazu Tsuno/AFP/Getty Images