GARDEZ, Afghanistan -- The Americans detained Akhtiar, the intelligence officer said, because they were given bad information by another Afghan who'd harbored a personal vendetta against Akhtiar going back to his time as a commander against the Soviet military during the 1980s.

"In some of these cases, tribal feuds and political feuds have played a big role" in people getting sent to Guantánamo, the intelligence officer said.

He didn't want his name used, partly because he didn't want to offend the Western officials he works with and partly because Afghan intelligence officers are assassinated regularly.

"There were Afghans being sent to Guantánamo because of bad intelligence," said Helaluddin Helal, Afghanistan's deputy interior minister for security from 2002 to early 2004. "In the beginning, everyone was trying to give intelligence to the Americans . . . the Americans were taking action without checking this information."

Nusrat Khan was in his 70s when American troops shoved him into an isolation cell at Bagram in the spring of 2003. They blindfolded him, put earphones on his head and tied his hands behind his back for almost four weeks straight, Khan said.

By the time he was taken out of the cell, Khan — who'd had at least two strokes years before he was arrested and was barely able to walk — was half-mad and couldn't stand without help. Khan said that he was taken to Guantánamo on a stretcher.

Several Afghan officials, including the country's attorney general, later said that Khan, who spent more than three years at Guantánamo, wasn't a threat to anyone; he'd been turned in as an insurgent leader because of decades-old rivalries with competing Afghan militias.

Ghalib Hassan was an Interior Ministry-appointed district commander in Afghanistan's Nangarhar province, a man who'd risked his life to help the U.S.-backed government. Din Mohammed, the former governor of that province and now the governor of Kabul, said there was no question that local tribal leaders, offended by Hassan's brusque style, fed false information about him to local informants used by American troops.

The Pentagon declined requests to make top officials, including the secretary of defense, available to respond to McClatchy's findings. The defense official in charge of detainee affairs, Sandra Hodgkinson, refused to speak with McClatchy.

The Pentagon's only response to a series of written questions from McClatchy, and to a list of 63 of the 66 former detainees interviewed for this story, was a three-paragraph statement.

"These unlawful combatants have provided valuable information in the struggle to protect the U.S. public from an enemy bent on murder of innocent civilians," Col. Gary Keck said in the statement. He provided no examples.

Rear Adm. Mark H. Buzby, until recently the commanding officer at Guantánamo, said that detainees had supplied crucial information about al Qaeda, the Taliban and other terrorist groups.

"Included with the folks that were brought here in 2002 were, by and large, the main leadership of al Qaeda and the Taliban," he said in a phone interview.

Buzby agreed, however, that some detainees were from the bottom rung.

"It's all about developing the mosaic . . . there's value to both ends of the spectrum," he said.