Obama makes unannounced visit to Afghanistan

President Obama steps off Air Force One upon arrival at Bagram air base, north of Kabul, Afghanistan.  (Mandel Ngan / AFP / Getty Images)

Security vehicles accompany President Obama’s motorcade en route to the Afghan presidential palace in Kabul.  (Charles Dharapak / Associated Press)

Members of the news media and President Obama’s entourage walk from Air Force One to waiting helicopters at Bagram air base in Afghanistan.   (Charles Dharapak / Associated Press)

President Obama arrives to address U.S. troops during his visit to Bagram air base.   (Mandel Ngan / AFP / Getty Images)

President Obama greets troops at Bagram air base.   (Mandel Ngan / AFP / Getty Images)

President Obama with the troops at Bagram air base.   (Charles Dharapak / Associated Press)

President Obama with the troops at Bagram air base.   (Mandel Ngan / AFP / Getty Images)

Marine Gen. John R. Allen, top commander of NATO and U.S. forces in Afghanistan, introduces President Obama before his speech to the troops at Bagram air base.   (Charles Dharapak / Associated Press)

President Obama addresses U.S. troops at Bagram air base.   (Mandel Ngan / AFP / Getty Images)

Afghan President Hamid Karzai and President Obama shake hands after signing a strategic partnership agreement at the presidential palace in the capital, Kabul.   (Mandel Ngan / AFP / Getty Images)