Afghan National Army soldiers stand guard at the main gate of the Parwan Detention Facility Center on the outskirts of Bagram. Afghan authorities released 65 prisoners from there Thursday. Massoud Hossaini/AP hide caption

itoggle caption Massoud Hossaini/AP

Afghan presidential candidates Qayum Karzai (from left), Ashraf Ghani and Abdullah Abdullah take part in a televised debate in Kabul on Saturday. With President Hamid Karzai stepping down, the presidential election set for April 5 will mark the first time the country has changed leaders at the ballot box. Wakil Kohsar/AFP/Getty Images hide caption

itoggle caption Wakil Kohsar/AFP/Getty Images

A campaign banner is posted in Kabul, Afghanistan, for presidential candidate Abdullah Abdullah on Sunday. Omar Sobhani/Reuters/Landov hide caption

itoggle caption Omar Sobhani/Reuters/Landov

Soldiers in the Afghan National Army's 6th Kandak (battalion), 3rd company, search a local farmer's poppy field during a joint patrol with U.S. forces in Kandahar province in March of last year. Andrew Burton/Getty Images hide caption

itoggle caption Andrew Burton/Getty Images

An Afghan security officer runs toward the scene of Friday's bombing in Kabul. Three NATO personnel were killed and at least six Afghan civilians were wounded. Omar Sobhani /Reuters /Landov hide caption

itoggle caption Omar Sobhani /Reuters /Landov