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U.S. President Obama meets with troops at Bagram Air Force Base in Kabul

U.S. President Barack Obama meets with troops at Bagram Air Base in Kabul, March 28, 2010. Obama arrived unannounced in Afghanistan on Sunday, his first visit to the war zone that could define his presidency since his election as U.S. commander-in-chief. Air Force One landed in darkness at Bagram airfield north of the Afghan capital, and Obama was whisked by helicopter to Hamid Karzai's palace in Kabul, where he was greeted by the Afghan president and a band playing the U.S. national anthem. REUTERS/Jim Young (AFGHANISTAN - Tags: MILITARY POLITICS IMAGES OF THE DAY)

Obama's presidential highlights

A look at the memorable moments of President Barack Obama's time in office.