Guantanamo may even be "a bit of a front," designed to distract al-Qaeda, he says. "It takes everybody's attention away from locations where big fish are being held. The secrecy surrounding it makes everybody think that very serious stuff is going on there."

American and foreign officials have also grown increasingly concerned about the prospect that detainees who arrived at Guantánamo representing little threat to the United States may have since been radicalized by the conditions of their imprisonment and others held with them.

''Guantánamo is a huge problem for Americans,'' a senior Arab intelligence official familiar with its operations said. ''Even those who were not hard-core extremists have now been indoctrinated by the true believers. Like any other prison, they have been taught to hate. If they let these people go, these people will make trouble.''

In late summer 2002, a senior C.I.A. analyst with extensive experience in the Middle East spent about a week at the prison camp observing and interviewing dozens of detainees, said officials who read his detailed memorandum.

While the survey was anecdotal, those officials said the document, which contained about 15 pages, concluded that a substantial number of the detainees appeared to be low-level militants, aspiring holy warriors who had rushed to Afghanistan to defend the Taliban, or simply innocents in the wrong place at the wrong time.

Senior military officials now readily acknowledge that many members of the intelligence team initially sent to Guantánamo were poorly prepared to sort through the captives. During the first half of 2002, they said, almost none of the Army interrogators had any substantial background in terrorism, Al Qaeda or other relevant subjects.

In interviews, the officials said at least five prisoners released from Guantánamo since early 2003 had rejoined the Taliban and resumed attacks on American and Afghan government forces. Although two American officials said only one of the former detainees had turned out to be an important figure, Afghan officials said all five men were in fact commanders with close contacts to the Taliban leadership.

The most notorious of the former Guántanamo detainees, Mullah Shahzada, had been a lieutenant to a senior commander when he was first captured in the war, an American military intelligence official said. After his return to Afghanistan in March 2003, he emerged as a frontline Taliban commander, Afghan officials said, leading a series of attacks in which at least 13 people were killed, including 2 aid workers.

Senior Pentagon officials refused to explain how Mr. Shahzada had talked his way out of Guantánamo. But two other military officials with knowledge of the case said he had given a false name and portrayed himself as having been captured by mistake.

''He stuck to his story and was fairly calm about the whole thing,'' a military intelligence official said. ''He maintained over a period time that he was nothing but an innocent rug merchant who just got snatched up.''

[...]

Afghan officials blamed the United States for the return of the five men to the Taliban's ranks, saying neither American military officials nor the Kabul police, who briefly process the detainees when they are sent home, consult them about the detainees they free.

''There are lots of people who were innocent, and they are capturing them, just on anyone's information,'' said Dr. Laghmani, the chief of the National Security Directorate in Kandahar. ''And then they are releasing guilty people.''