But what becomes of a detainee when he's sent home? CBS News correspondent David Martin reports that in many cases, they go right back to their former life.
Nearly one out of every five prisoners released from Guantanamo has gone back to terrorism.
The latest figures compiled by the Defense Intelligence Agency show that 18 percent of more than 530 prisoners sent home or to another country are confirmed or suspected of what the Pentagon calls "terrorist activities."
That works out to nearly 100 former detainees back in the fight.
The so-called recidivism rate has increased most dramatically in the past two years, which suggests that the longer you are held at Guantanamo the more likely you are to return to terrorism.
Lawyers who represent Guantanamo inmates claim the prison itself - indefinite detention without being convicted of any crime - drives them to terrorism. But CBS News consultant and former Bush administration official Juan Zarate says the ones being released now are more likely to be genuine terrorists.
"You've had individuals who are released who are harder core, more tied to the terrorist networks and more ideologically committed," he said.
Some have shown up in al Qaeda videos and at least one has carried out a suicide bombing. Others are back in Afghanistan fighting Americans.
The No. 3 Taliban commander in southern Afghanistan - where 4,000 marines are currently fighting - was once a prisoner at Guantanamo, as was the man who is now chief of the Taliban's military committee.
"The U.S. government has to take calculated risks and to a certain extent rely on the good faith and efforts of other governments and sometimes that calculus just doesn't work out," Zarate said.
Defense officials expect the number of former inmates who return to terrorism to go higher before Guantanamo is closed.