U.S. Marines take cover as they are involved in a gun battle in March during a patrol in Marjah, Afghanistan. In February, U.S.-led troops set out to rid the area of insurgents and set up a viable local government. But Taliban militants have returned to the area. Dusan Vranic/AP hide caption

itoggle caption Dusan Vranic/AP

In this courtroom sketch, some of the defendants are seen in Manhattan federal court in New York on Monday. They are among 11 people the FBI has arrested for allegedly serving for years as secret agents of Russia's intelligence agency, the SVR, with the goal of penetrating U.S. government policymaking circles. Elizabeth Williams/AP hide caption

itoggle caption Elizabeth Williams/AP

Gen. William K. Harrison, Jr., seated at left, and North Korean Gen. Nam Il, seated at right, sign armistice documents in Armistice Hall in Panmunjom, a no man's land between the Koreas, on July 26, 1953. AP hide caption

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President Obama stands with Gen. David Petraeus (right) and Vice President Biden on Wednesday in the Rose Garden as he announces that Petraeus will replace Gen. Stanley McChrystal. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP