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

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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

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Mark Wilson/Getty Images