The U.S. military on Thursday disclosed that it delivered 10 Yemeni captives to the Arabian Sea nation of Oman in the largest Guantanamo release to a single country by the Obama administration.The military operation — which leaked earlier in the week without disclosure of the destination — left 93 captives at the remote prison, 34 of them cleared for transfer with security arrangements that satisfy Secretary of Defense Ash Carter. For his part, Carter vowed to work with Congress "as we diligently work to close this chapter in our history."None of the 10 released this week were ever charged with a crime in more than a decade of U.S. military custody.RELATED: 6 of the first 20 'worst of the worst' still captive at Guantanamo Rather, they were held as war-on-terror detainees at the remote U.S. Navy base in Cuba from the earliest days of the prison camps in 2002. Most arrived when they were in their early 20s, according to their leaked 2008 prison profiles, which portrayed them as recruits to the jihad who got to Afghanistan in the weeks or months before Sept. 11, 2001, too late to have had a role in the terror attacks.Among those released was Samir al Hassan Moqbel, 38, who got there the day the prison opened 14 years ago this week, and briefly captured attention with his April 2013 New York Times op-ed column about his hunger strike and forced feedings, "Gitmo Is Killing Me."Lee Wolosky, the State Department special envoy for the closure of the prison, credited "sustained diplomatic engagement" for what he called "this important milestone.""We are very grateful to our friends and partners in the Gulf and elsewhere who have resettled Yemeni detainees," he added in a statement that predicted the U.S. would be poised "to empty Guantanamo" of the 34 currently approved detainees "by this summer."In general the Obama administration had preferred smaller, more tailored transfers, and in fact sent two earlier groups of four and then six Yemenis to Oman last year, six months apart.The downsizing, which occurred Wednesday, was disclosed on the last morning of the stewardship of the prison by Marine Gen. John F. Kelly, the retiring commander of U.S. Southern Command, who hinted at the transfer last week."If they go back to the fight, we'll probably kill them," he said last week at a Pentagon news conference. "So that's a good thing."Carter called the release the product of "a deliberate and careful review" during remarks at SouthCom when he installed Adm. Kurt Tidd as the new SouthCom commander. Carter said Tidd's responsibilities would include "to bring the detention facility at Guantanamo Bay to a responsible close."He reminded that, while some of the last 93 captives could be release to other countries, ending prison operations at Guantanamo would require bringing others "to an appropriate, secure location in the United States." Congress has forbidden it.