In the windowless, jet-black garage-size room, some soldiers beat prisoners with rifle butts, yelled and spit in their faces and, in a nearby area, used detainees for target practice in a game of jailer paintball. Their intention was to extract information to help hunt down Iraq's most-wanted terrorist, Abu Musab al-Zarqawi, according to Defense Department personnel who served with the unit or were briefed on its operations.

The Black Room was part of a temporary detention site at Camp Nama, the secret headquarters of a shadowy military unit known as Task Force 6-26. Located at Baghdad International Airport, the camp was the first stop for many insurgents on their way to the Abu Ghraib prison a few miles away.

Placards posted by soldiers at the detention area advised, "NO BLOOD, NO FOUL." The slogan, as one Defense Department official explained, reflected an adage adopted by Task Force 6-26: "If you don't make them bleed, they can't prosecute for it." According to Pentagon specialists who worked with the unit, prisoners at Camp Nama often disappeared into a detention black hole, barred from access to lawyers or relatives, and confined for weeks without charges. "The reality is, there were no rules there," another Pentagon official said.

The story of detainee abuse in Iraq is a familiar one. But the following account of Task Force 6-26, based on documents and interviews with more than a dozen people, offers the first detailed description of how the military's most highly trained counterterrorism unit committed serious abuses.

It adds to the picture of harsh interrogation practices at American military prisons in Afghanistan and Guantánamo Bay, Cuba, as well as at secret Central Intelligence Agency detention centers around the world.

The new account reveals the extent to which the unit members mistreated prisoners months before and after the photographs of abuse from Abu Ghraib were made public in April 2004, and it helps belie the original Pentagon assertions that abuse was confined to a small number of rogue reservists at Abu Ghraib.

The abuses at Camp Nama continued despite warnings beginning in August 2003 from an Army investigator and American intelligence and law enforcement officials in Iraq. The C.I.A. was concerned enough to bar its personnel from Camp Nama that August.

It is difficult to compare the conditions at the camp with those at Abu Ghraib because so little is known about the secret compound, which was off limits even to the Red Cross. The abuses appeared to have been unsanctioned, but some of them seemed to have been well known throughout the camp.

For an elite unit with roughly 1,000 people at any given time, Task Force 6-26 seems to have had a large number of troops punished for detainee abuse. Since 2003, 34 task force members have been disciplined in some form for mistreating prisoners, and at least 11 members have been removed from the unit, according to new figures the Special Operations Command provided in response to questions from The New York Times. Five Army Rangers in the unit were convicted three months ago for kicking and punching three detainees in September 2005.

Some of the serious accusations against Task Force 6-26 have been reported over the past 16 months by news organizations including NBC, The Washington Post and The Times. Many details emerged in hundreds of pages of documents released under a Freedom of Information Act request by the American Civil Liberties Union. But taken together for the first time, the declassified documents and interviews with more than a dozen military and civilian Defense Department and other federal personnel provide the most detailed portrait yet of the secret camp and the inner workings of the clandestine unit.

The documents and interviews also reflect a culture clash between the free-wheeling military commandos and the more cautious Pentagon civilians working with them that escalated to a tense confrontation. At one point, one of Defense Secretary Donald H. Rumsfeld's top aides, Stephen A. Cambone, ordered a subordinate to "get to the bottom" of any misconduct.

Most of the people interviewed for this article were midlevel civilian and military Defense Department personnel who worked with Task Force 6-26 and said they witnessed abuses, or who were briefed on its operations over the past three years.

Many were initially reluctant to discuss Task Force 6-26 because its missions are classified. But when pressed repeatedly by reporters who contacted them, they agreed to speak about their experiences and observations out of what they said was anger and disgust over the unit's treatment of detainees and the failure of task force commanders to punish misconduct more aggressively. The critics said the harsh interrogations yielded little information to help capture insurgents or save American lives.

Virtually all of those who agreed to speak are career government employees, many with previous military service, and they were granted anonymity to encourage them to speak candidly without fear of retribution from the Pentagon. Many of their complaints are supported by declassified military documents and e-mail messages from F.B.I. agents who worked regularly with the task force in Iraq.

A Demand for Intelligence

Military officials say there may have been extenuating circumstances for some of the harsh treatment at Camp Nama and its field stations in other parts of Iraq. By the spring of 2004, the demand on interrogators for intelligence was growing to help combat the increasingly numerous and deadly insurgent attacks.

Some detainees may have been injured resisting capture. A spokesman for the Special Operations Command, Kenneth S. McGraw, said there was sufficient evidence to prove misconduct in only 5 of 29 abuse allegations against task force members since 2003. As a result of those five incidents, 34 people were disciplined.

"We take all those allegations seriously," Gen. Bryan D. Brown, the commander of the Special Operations Command, said in a brief hallway exchange on Capitol Hill on March 8. "Any kind of abuse is not consistent with the values of the Special Operations Command."

The secrecy surrounding the highly classified unit has helped to shield its conduct from public scrutiny. The Pentagon will not disclose the unit's precise size, the names of its commanders, its operating bases or specific missions. Even the task force's name changes regularly to confuse adversaries, and the courts-martial and other disciplinary proceedings have not identified the soldiers in public announcements as task force members.

General Brown's command declined requests for interviews with several former task force members and with Lt. Gen. Stanley McChrystal, who leads the Joint Special Operations Command, the headquarters at Fort Bragg, N.C., that supplies the unit's most elite troops.

One Special Operations officer and a senior enlisted soldier identified by Defense Department personnel as former task force members at Camp Nama declined to comment when contacted by telephone. Attempts to contact three other Special Operations soldiers who were in the unit — by phone, through relatives and former neighbors — were also unsuccessful.

Cases of detainee abuse attributed to Task Force 6-26 demonstrate both confusion over and, in some cases, disregard for approved interrogation practices and standards for detainee treatment, according to Defense Department specialists who have worked with the unit.

In early 2004, an 18-year-old man suspected of selling cars to members of the Zarqawi terrorist network was seized with his entire family at their home in Baghdad. Task force soldiers beat him repeatedly with a rifle butt and punched him in the head and kidneys, said a Defense Department specialist briefed on the incident.

Some complaints were ignored or played down in a unit where a conspiracy of silence contributed to the overall secretiveness. "It's under control," one unit commander told a Defense Department official who complained about mistreatment at Camp Nama in the spring of 2004.

For hundreds of suspected insurgents, Camp Nama was a way station on a journey that started with their capture on the battlefield or in their homes, and ended often in a cell at Abu Ghraib. Hidden in plain sight just off a dusty road fronting Baghdad International Airport, Camp Nama was an unmarked, virtually unknown compound at the edge of the taxiways.

The heart of the camp was the Battlefield Interrogation Facility, alternately known as the Temporary Detention Facility and the Temporary Holding Facility. The interrogation and detention areas occupied a corner of the larger compound, separated by a fence topped with razor wire.

Unmarked helicopters flew detainees into the camp almost daily, former task force members said. Dressed in blue jumpsuits with taped goggles covering their eyes, the shackled prisoners were led into a screening room where they were registered and examined by medics.

Just beyond the screening rooms, where Saddam Hussein was given a medical exam after his capture, detainees were kept in as many as 85 cells spread over two buildings. Some detainees were kept in what was known as Motel 6, a group of crudely built plywood shacks that reeked of urine and excrement. The shacks were cramped, forcing many prisoners to squat or crouch. Other detainees were housed inside a separate building in 6-by-8-foot cubicles in a cellblock called Hotel California.

The interrogation rooms were stark. High-value detainees were questioned in the Black Room, nearly bare but for several 18-inch hooks that jutted from the ceiling, a grisly reminder of the terrors inflicted by Mr. Hussein's inquisitors. Jailers often blared rap music or rock 'n' roll at deafening decibels over a loudspeaker to unnerve their subjects.

Another smaller room offered basic comforts like carpets and cushioned seating to put more cooperative prisoners at ease, said several Defense Department specialists who worked at Camp Nama. Detainees wore heavy, olive-drab hoods outside their cells. By June 2004, the revelations of abuse at Abu Ghraib galvanized the military to promise better treatment for prisoners. In one small concession at Camp Nama, soldiers exchanged the hoods for cloth blindfolds with drop veils that allowed detainees to breathe more freely but prevented them from peeking out.

Some former task force members said the Nama in the camp's name stood for a coarse phrase that soldiers used to describe the compound. One Defense Department specialist recalled seeing pink blotches on detainees' clothing as well as red welts on their bodies, marks he learned later were inflicted by soldiers who used detainees as targets and called themselves the High Five Paintball Club.

Mr. McGraw, the military spokesman, said he had not heard of the Black Room or the paintball club and had not seen any mention of them in the documents he had reviewed.

In a nearby operations center, task force analysts pored over intelligence collected from spies, detainees and remotely piloted Predator surveillance aircraft, to piece together clues to aid soldiers on their raids. Twice daily at noon and midnight military interrogators and their supervisors met with officials from the C.I.A., F.B.I. and allied military units to review operations and new intelligence.

Task Force 6-26 was a creation of the Pentagon's post-Sept. 11 campaign against terrorism, and it quickly became the model for how the military would gain intelligence and battle insurgents in the future. Originally known as Task Force 121, it was formed in the summer of 2003, when the military merged two existing Special Operations units, one hunting Osama bin Laden in and around Afghanistan, and the other tracking Mr. Hussein in Iraq. (Its current name is Task Force 145.)

The task force was a melting pot of military and civilian units. It drew on elite troops from the Joint Special Operations Command, whose elements include the Army unit Delta Force, Navy's Seal Team 6 and the 75th Ranger Regiment. Military reservists and Defense Intelligence Agency personnel with special skills, like interrogators, were temporarily assigned to the unit. C.I.A. officers, F.B.I. agents and special operations forces from other countries also worked closely with the task force.

Many of the American Special Operations soldiers wore civilian clothes and were allowed to grow beards and long hair, setting them apart from their uniformed colleagues. Unlike conventional soldiers and marines whose Iraq tours lasted 7 to 12 months, unit members and their commanders typically rotated every 90 days.

Task Force 6-26 had a singular focus: capture or kill Mr. Zarqawi, the Jordanian militant operating in Iraq. "Anytime there was even the smell of Zarqawi nearby, they would go out and use any means possible to get information from a detainee," one official said.

Defense Department personnel briefed on the unit's operations said the harsh treatment extended beyond Camp Nama to small field outposts in Baghdad, Falluja, Balad, Ramadi and Kirkuk. These stations were often nestled within the alleys of a city in nondescript buildings with suburban-size yards where helicopters could land to drop off or pick up detainees.

At the outposts, some detainees were stripped naked and had cold water thrown on them to cause the sensation of drowning, said Defense Department personnel who served with the unit.

In January 2004, the task force captured the son of one of Mr. Hussein's bodyguards in Tikrit. The man told Army investigators that he was forced to strip and that he was punched in the spine until he fainted, put in front of an air-conditioner while cold water was poured on him and kicked in the stomach until he vomited. Army investigators were forced to close their inquiry in June 2005 after they said task force members used battlefield pseudonyms that made it impossible to identify and locate the soldiers involved. The unit also asserted that 70 percent of its computer files had been lost.

Despite the task force's access to a wide range of intelligence, its raids were often dry holes, yielding little if any intelligence and alienating ordinary Iraqis, Defense Department personnel said. Prisoners deemed no threat to American troops were often driven deep into the Iraqi desert at night and released, sometimes given $100 or more in American money for their trouble.

Back at Camp Nama, the task force leaders established a ritual for departing personnel who did a good job, Pentagon officials said. The commanders presented them with two unusual mementos: a detainee hood and a souvenir piece of tile from the medical screening room that once held Mr. Hussein.

Early Signs of Trouble

Accusations of abuse by Task Force 6-26 came as no surprise to many other officials in Iraq. By early 2004, both the C.I.A. and the F.B.I. had expressed alarm about the military's harsh interrogation techniques.

The C.I.A.'s Baghdad station sent a cable to headquarters on Aug. 3, 2003, raising concern that Special Operations troops who served with agency officers had used techniques that had become too aggressive. Five days later, the C.I.A. issued a classified directive that prohibited its officers from participating in harsh interrogations. Separately, the C.I.A. barred its officers from working at Camp Nama but allowed them to keep providing target information and other intelligence to the task force.

The warnings still echoed nearly a year later. On June 25, 2004, nearly two months after the disclosure of the abuses at Abu Ghraib, an F.B.I. agent in Iraq sent an e-mail message to his superiors in Washington, warning that a detainee captured by Task Force 6-26 had suspicious burn marks on his body. The detainee said he had been tortured. A month earlier, another F.B.I. agent asked top bureau officials for guidance on how to deal with military interrogators across Iraq who used techniques like loud music and yelling that exceeded "the bounds of standard F.B.I. practice."

American generals were also alerted to the problem. In December 2003, Col. Stuart A. Herrington, a retired Army intelligence officer, warned in a confidential memo that medical personnel reported that prisoners seized by the unit, then known as Task Force 121, had injuries consistent with beatings. "It seems clear that TF 121 needs to be reined in with respect to its treatment of detainees," Colonel Herrington concluded.

By May 2004, just as the scandal at Abu Ghraib was breaking, tensions increased at Camp Nama between the Special Operations troops and civilian interrogators and case officers from the D.I.A.'s Defense Human Intelligence Service, who were there to support the unit in its fight against the Zarqawi network. The discord, according to documents, centered on the harsh treatment of detainees as well as restrictions the Special Operations troops placed on their civilian colleagues, like monitoring their e-mail messages and phone calls.

Maj. Gen. George E. Ennis, who until recently commanded the D.I.A.'s human intelligence division, declined to be interviewed for this article. But in written responses to questions, General Ennis said he never heard about the numerous complaints made by D.I.A. personnel until he and his boss, Vice Adm. Lowell E. Jacoby, then the agency's director, were briefed on June 24, 2004.

The next day, Admiral Jacoby wrote a two-page memo to Mr. Cambone, under secretary of defense for intelligence. In it, he described a series of complaints, including a May 2004 incident in which a D.I.A. interrogator said he witnessed task force soldiers punch a detainee hard enough to require medical help. The D.I.A. officer took photos of the injuries, but a supervisor confiscated them, the memo said.

The tensions laid bare a clash of military cultures. Combat-hardened commandos seeking a steady flow of intelligence to pinpoint insurgents grew exasperated with civilian interrogators sent from Washington, many of whom were novices at interrogating hostile prisoners fresh off the battlefield.

"These guys wanted results, and our debriefers were used to a civil environment," said one Defense Department official who was briefed on the task force operations.

Within days after Admiral Jacoby sent his memo, the D.I.A. took the extraordinary step of temporarily withdrawing its personnel from Camp Nama.

Admiral Jacoby's memo also provoked an angry reaction from Mr. Cambone. "Get to the bottom of this immediately. This is not acceptable," Mr. Cambone said in a handwritten note on June 26, 2004, to his top deputy, Lt. Gen. William G. Boykin. "In particular, I want to know if this is part of a pattern of behavior by TF 6-26."

General Boykin said through a spokesman on March 17 that at the time he told Mr. Cambone he had found no pattern of misconduct with the task force.

A Shroud of Secrecy

Military and legal experts say the full breadth of abuses committed by Task Force 6-26 may never be known because of the secrecy surrounding the unit, and the likelihood that some allegations went unreported.

In the summer of 2004, Camp Nama closed and the unit moved to a new headquarters in Balad, 45 miles north of Baghdad. The unit's operations are now shrouded in even tighter secrecy.

Soon after their rank-and-file clashed in 2004, D.I.A. officials in Washington and military commanders at Fort Bragg agreed to improve how the task force integrated specialists into its ranks. The D.I.A. is now sending small teams of interrogators, debriefers and case officers, called "deployable Humint teams," to work with Special Operations forces in Iraq and Afghanistan.

Senior military commanders insist that the elite warriors, who will be relied on more than ever in the campaign against terrorism, are now treating detainees more humanely and can police themselves. The C.I.A. has resumed conducting debriefings with the task force, but does not permit harsh questioning, a C.I.A. official said.

General McChrystal, the leader of the Joint Special Operations Command, received his third star in a promotion ceremony at Fort Bragg on March 13.

On Dec. 8, 2004, the Pentagon's spokesman, Lawrence Di Rita, said that four Special Operations soldiers from the task force were punished for "excessive use of force" and administering electric shocks to detainees with stun guns. Two of the soldiers were removed from the unit. To that point, Mr. Di Rita said, 10 task force members had been disciplined. Since then, according to the new figures provided to The Times, the number of those disciplined for detainee abuse has more than tripled. Nine of the 34 troops disciplined received written or oral counseling. Others were reprimanded for slapping detainees and other offenses.

The five Army Rangers who were court-martialed in December received punishments including jail time of 30 days to six months and reduction in rank. Two of them will receive bad-conduct discharges upon completion of their sentences.

Human rights advocates and leading members of Congress say the Pentagon must still do more to hold senior-level commanders and civilian officials accountable for the misconduct.

The Justice Department inspector general is investigating complaints of detainee abuse by Task Force 6-26, a senior law enforcement official said. The only wide-ranging military inquiry into prisoner abuse by Special Operations forces was completed nearly a year ago by Brig. Gen. Richard P. Formica, and was sent to Congress.

But the United States Central Command has refused repeated requests from The Times over the past several months to provide an unclassified copy of General Formica's findings despite Mr. Rumsfeld's instructions that such a version of all 12 major reports into detainee abuse be made public.