Canadian-born Omar Khadr is seen in a courtroom sketch during a 2010 hearing at the U.S. military prison at Guantanamo Bay, Cuba. He was moved to a Canadian prison in 2012. Janet Hamlin/AP hide caption

itoggle caption Janet Hamlin/AP

A shackled detainee is transported by guards, including a female soldier, at Camp Delta detention center, Guantanamo Bay U.S. Naval Base, Cuba, in this photo from December 2006. Brennan Linsley/AP hide caption

itoggle caption Brennan Linsley/AP

Brig. Gen. Viet Luong of the 1st Cavalry Division came to the United States in the 1970s after his family fled Vietnam in the waning days of the war there. He's now leading the effort to train Afghan soldiers to fight the Taliban. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

The entrance to Camp 5 and Camp 6 at the U.S. military's Guantanamo Bay detention center at Guantanamo Bay Naval Base, Cuba, in a photograph taken in 2014. Ben Fox/AP hide caption

itoggle caption Ben Fox/AP