Displaced people from the minority Yazidi sect walk toward the Syrian border on the outskirts of Sinjar mountain on Monday. A U.S. assessment team says far fewer refugees are stranded on Mount Sinjar than previously thought. Reuters/Landov hide caption

itoggle caption Reuters/Landov

GOP leadership decided against keeping an immigration-related provision in the defense authorization bill. But it allowed one banning the Defense Department from participating in climate change research. Carolyn Kaster/AP hide caption

itoggle caption Carolyn Kaster/AP

Defense Secretary Chuck Hagel briefs reporters at the Pentagon on Monday. Hagel and President Obama will need to fight through a wall of resistance to their proposed defense budget cuts, say former members of a defense base closing commission. Carolyn Kaster/AP hide caption

itoggle caption Carolyn Kaster/AP

A photo provided by Lockheed Martin shows a test of its THAAD missile interceptor system. The Pentagon has awarded a contract worth more than $3.9 billion for the system. Lockheed Martin hide caption

itoggle caption Lockheed Martin

New Defense Secretary Chuck Hagel, left, as he was sworn in Wednesday morning at the Pentagon. His wife, Lilibet, held the Bible. Michael L. Rhodes, the Pentagon's director of administration and management, administered the oath. MC1 Chad J. McNeeley/Office of the Secretary of Defense hide caption

itoggle caption MC1 Chad J. McNeeley/Office of the Secretary of Defense

President Obama nominates former Sen. Chuck Hagel, R-Neb., to be defense secretary Monday at the White House. Mark Wilson/Getty Images hide caption

itoggle caption Mark Wilson/Getty Images