U.S. soldiers in Afghanistan walk away from a helicopter at Forward Operating Base Connelly in the eastern province of Nangarhar on Aug. 13. The U.S. formally ended combat operations in Afghanistan at the end of last year. But nearly 10,000 American troops remain in the country and the U.S. frequently carries out air sorties. Fourteen American military personnel have died in Afghanistan this year. Wakil Kohsar/AFP/Getty Images hide caption

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Doctors Without Borders President Joanne Liu (right) is calling for an international fact-finding investigation into a U.S. airstrike on one of the charity's hospitals. Fabrice Coffrini/AFP/Getty Images hide caption

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The trauma center operated in Kunduz by Doctors Without Borders was in flames after U.S. airstrikes on Saturday that left 22 dead, including medical staff and patients. AP hide caption

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The burned Doctors Without Borders hospital is seen after explosions in the northern Afghan city of Kunduz on Saturday. Doctors Without Borders says 12 staff members and 10 patients were killed in the attack and 37 others were wounded. AP hide caption

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Smoke rises from Kunduz, Afghanistan on Thursday. Government forces have reportedly retaken the city after it was seized by the Taliban on Monday. AP hide caption

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On May 21, an Afghan child is treated at a Doctors Without Borders hospital in the northern city of Kunduz, after being injured in a fight between the Taliban and Afghan security forces. Shah Marai/AFP/Getty Images hide caption

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