WASHINGTON -- Faced with the worst-ever foreign attack on American soil, the U.S. military set up a human intelligence laboratory at Guantánamo that used interrogation and detention practices they largely made up as they went along.

The world may have thought the U.S. was detaining a band of international terrorists whose questioning would help the hunt for Osama bin Laden or foil the next 9/11.

But a collection of secret intelligence documents from George W. Bush's administration, not meant to surface for 20 years, shows that the military's efforts at Guantánamo often were much less effective than the government has acknowledged. Viewed as a whole, the secret intelligence summaries help explain why in May 2009 President Barack Obama, after ordering his own review of wartime intelligence, called America's experiment at Guantánamo "quite simply a mess."

The documents, more than 750 individual assessments of former and current Guantánamo detainees, show an intelligence operation that was tremendously dependent on informants - both prison-camp snitches repeating what they'd heard from fellow captives and self-described, at times self-aggrandizing, former al-Qaeda insiders turned government witnesses who Pentagon records show have since been released.

Intelligence analysts are at odds with each other over which informants to trust, at times drawing inferences from prisoners exercise habits. They ordered DNA tests, tethered Taliban suspects to polygraphs, strung together tidbits at times in ways that seemed to defy common sense.

The documents also show that in the earliest years of the prison camp's operation, the Pentagon permitted Chinese and Russian interrogators into the camps - information from those sessions are included in some captives' assessments - something American defense lawyers working free for the foreign prisoners have alleged and protested for years.

Guantánamo analysts at times questioned the reliability of some information gleaned from other detainees' interrogations.

Allegations and information from one Yemeni, no longer at Guantánamo, appears in at least 135 detainees' files, prompting Navy Rear Adm. Dave Thomas, the prison camps commander in August 2008, to include this warning:

"Any information provided should be adequately verified through other sources before being utilized."

The same report goes on to praise the captive as an "invaluable intelligence source" for information about "al Qaeda and Taliban training, operations, personnel and facilities," and warns that he'd be at risk of retaliation if he were released into Yemeni society. He was resettled in Europe by the Obama administration.

In fact, information from just eight men showed up in risk-assessment forms for at least 235 Guantánamo detainees — some 30 percent of those known to have been held there.

In many cases, the detainees made direct allegations of others' involvement in militant activities; in others, they gave contextual information used to help build the edges of a case.

Yet there's not a whiff in the documents that any of the work is leading the U.S. closer to capturing bin Laden. In fact, they suggest a sort of mission creep beyond the post-9/11 goal of using interrogations to hunt down the al Qaeda inner circle and sleeper cells.

The file of one captive who now lives in Ireland shows that he was sent to Guantánamo to let U.S. military intelligence gather information on the secret service of Uzbekistan. A man from Bahrain was sent to Guantánamo in June 2002, in part, for interrogation on "personalities in the Bahraini court."