along Walnut Creek

One night in mid-April, the steel door clanked shut on detainee No. 200343 at Camp Cropper, the United States military’s maximum-security detention site in Baghdad.

American guards arrived at the man’s cell periodically over the next several days, shackled his hands and feet, blindfolded him and took him to a padded room for interrogation, the detainee said. After an hour or two, he was returned to his cell, fatigued but unable to sleep.

The fluorescent lights in his cell were never turned off, he said. At most hours, heavy metal or country music blared in the corridor. He said he was rousted at random times without explanation and made to stand in his cell. Even lying down, he said, he was kept from covering his face to block out the light, noise and cold. And when he was released after 97 days he was exhausted, depressed and scared.

Detainee 200343 was among thousands of people who have been held and released by the American military in Iraq, and his account of his ordeal has provided one of the few detailed views of the Pentagon’s detention operations since the abuse scandals at Abu Ghraib. Yet in many respects his case is unusual.

At Camp Cropper, he took notes on his imprisonment and smuggled them out in a Bible.

"Sick, very. Vomited," he wrote July 3. The next day: "Told no more phone calls til leave."

Nathan Ertel, the American held with Mr. Vance, brought away military records that shed further light on the detention camp and its secretive tribunals. Those records include a legal memorandum explicitly denying detainees the right to a lawyer at detention hearings to determine whether they should be released or held indefinitely, perhaps for prosecution.

The story told through those records and interviews illuminates the haphazard system of detention and prosecution that has evolved in Iraq, where detainees are often held for long periods without charges or legal representation, and where the authorities struggle to sort through the endless stream of detainees to identify those who pose real threats.

"Even Saddam Hussein had more legal counsel than I ever had," said Mr. Vance, who said he planned to sue the former defense secretary, Donald H. Rumsfeld, on grounds that his constitutional rights had been violated. "While we were detained, we wrote a letter to the camp commandant stating that the same democratic ideals we are trying to instill in the fledgling democratic country of Iraq, from simple due process to the Magna Carta, we are absolutely, positively refusing to follow ourselves."

A spokeswoman for the Pentagon’s detention operations in Iraq, First Lt. Lea Ann Fracasso, said in written answers to questions that the men had been "treated fair and humanely," and that there was no record of either man complaining about their treatment.

Held as ‘a Threat’

She said officials did not reach Mr. Vance’s contact at the F.B.I. until he had been in custody for three weeks. Even so, she said, officials determined that he "posed a threat" and decided to continue holding him. He was released two months later, Lieutenant Fracasso said, based on a "subsequent re-examination of his case," and his stated plans to leave Iraq.

Mr. Ertel, 30, a contract manager who knew Mr. Vance from an earlier job in Iraq, was released more quickly.

Mr. Vance went to Iraq in 2004, first to work for a Washington-based company. He later joined a small Baghdad-based security company where, he said, "things started looking weird to me." He said that the company, which was protecting American reconstruction organizations, had hired guards from a sheik in Basra and that many of them turned out to be members of militias whom the clients did not want around.

Mr. Vance said the company had a growing cache of weapons it was selling to suspicious customers, including a steady flow of officials from the Iraqi Interior Ministry. The ministry had ties to violent militias and death squads. He said he had also witnessed another employee giving American soldiers liquor in exchange for bullets and weapon repairs.

On a visit to Chicago in October 2005, Mr. Vance met twice with an F.B.I. agent who set up a reporting system. Weekly, Mr. Vance phoned the agent from Iraq and sent him e-mail messages. "It was like, ‘Hey, I heard this and I saw this.’ I wanted to help," Mr. Vance said. A government official familiar with the arrangement confirmed Mr. Vance’s account.

In April, Mr. Ertel and Mr. Vance said, they felt increasingly uncomfortable at the company. Mr. Ertel resigned and company officials seized the identification cards that both men needed to move around Iraq or leave the country.

On April 15, feeling threatened, Mr. Vance phoned the United States Embassy in Baghdad. A military rescue team rushed to the security company. Again, Mr. Vance described its operations, according to military records.

"Internee Vance indicated a large weapons cache was in the compound in the house next door," Capt. Plymouth D. Nelson, a military detention official, wrote in a memorandum dated April 22, after the men were detained. "A search of the house and grounds revealed two large weapons caches."

On the evening of April 15, they met with American officials at the embassy and stayed overnight. But just before dawn, they were awakened, handcuffed with zip ties and made to wear goggles with lenses covered by duct tape. Put into a Humvee, Mr. Vance said he asked for a vest and helmet, and was refused.

They were driven through dangerous Baghdad roads and eventually to Camp Cropper. They were placed in cells at Compound 5, the high-security unit where Saddam Hussein has been held.

Only days later did they receive an explanation: They had become suspects for having associated with the people Mr. Vance tried to expose.

"You have been detained for the following reasons: You work for a business entity that possessed one or more large weapons caches on its premises and may be involved in the possible distribution of these weapons to insurgent/terrorist groups," Mr. Ertel’s detention notice said.

Mr. Vance said he began seeking help even before his cell door closed for the first time. "They took off my blindfold and earmuffs and told me to stand in a corner, where they cut off the zip ties, and told me to continue looking straight forward and as I’m doing this, I’m asking for an attorney," he said. " ‘I want an attorney now,’ I said, and they said, ‘Someone will be here to see you.’ "

Instead, they were given six-digit ID numbers. The guards shortened Mr. Vance’s into something of a nickname: "343." And the routine began.

Bread and powdered drink for breakfast and sometimes a piece of fruit. Rice and chicken for lunch and dinner. Their cells had no sinks. The showers were irregular. They got 60 minutes in the recreation yard at night, without other detainees.

Five times in the first week, guards shackled the prisoners’ hands and feet, covered their eyes, placed towels over their heads and put them in wheelchairs to be pushed to a room with a carpeted ceiling and walls. There they were questioned by an array of officials who, they said they were told, represented the F.B.I., the C.I.A., the Naval Criminal Investigative Service and the Defense Intelligence Agency.

"It’s like boom, boom, boom," Mr. Ertel said. "They are drilling you. ‘We know you did this, you are part of this gun smuggling thing.’ And I’m saying you have it absolutely way off."

The two men slept in their 9-by-9-foot cells on concrete slabs, with worn three-inch foam mats. With the fluorescent lights on and the temperature in the 50s, Mr. Vance said, "I paced myself to sleep, walking until I couldn’t anymore. I broke the straps on two pair of flip-flops."

Asked about the lights, the detainee operations spokeswoman said that the camp’s policy was to turn off cell lights at night "to allow detainees to sleep."

A Psychological Game

One day, Mr. Vance met with a camp psychologist. "He realized I was having difficulties," Mr. Vance said. "He said to turn it into a game. He said: ‘I want you to pretend you are a soldier who has been kidnapped, and that you still have a duty to do. Memorize everything you can about everything that happens to you. Make it like you are a spy on the inside.’ I think he called it rational emotive behavioral therapy, and I started doing that."

Camp Rule 31 barred detainees from writing on the white cell walls, which were bare except for a black crescent moon painted on one wall to indicate the direction of Mecca for prayers. But Mr. Vance began keeping track of the days by making hash marks on the wall, and he also began writing brief notes that he hid in the Bible given to him by guards.

"Turned in request for dentist + phone + embassy letter + request for clothes," he wrote one day.

"Boards," he wrote April 24, the day he and Mr. Ertel went before Camp Cropper’s Detainee Status Board.

Their legal rights, laid out in a letter from Lt. Col. Bradley J. Huestis of the Army, the president of the status board, allowed them to attend the hearing and testify. However, under Rule 3, the letter said, "You do not have the right to legal counsel, but you may have a personal representative assist you at the hearing if the personal representative is reasonably available."

Mr. Vance and Mr. Ertel were permitted at their hearings only because they were Americans, Lieutenant Fracasso said. The cases of all other detainees are reviewed without the detainees present, she said. In both types of cases, defense lawyers are not allowed to attend because the hearings are not criminal proceedings, she said.

Lieutenant Fracasso said that currently there were three Americans in military custody in Iraq. The military does not identify detainees.

Mr. Vance and Mr. Ertel had separate hearings. They said their requests to be each other’s personal representative had been denied.

At the hearings, a woman and two men wearing Army uniforms but no name tags or rank designations sat a table with two stacks of documents. One was about an inch thick, and the men were allowed to see some papers from that stack. The other pile was much thicker, but they were told that this pile was evidence only the board could see.

The men pleaded with the board. "I’m telling them there has been a major mix-up," Mr. Ertel said. "Please, I’m out of my mind. I haven’t slept. I’m not eating. I’m terrified."

Mr. Vance said he implored the board to delve into his laptop computer and cellphone for his communications with the F.B.I. agent in Chicago.

Each of the hearings lasted about two hours, and the men said they never saw the board again.

"At the end, my first question was, ‘Does my family know I’m alive?’ and the lead man said, ‘I don’t know,’ " Mr. Vance recounted. "And then I asked when will we have an answer, and they said on average it takes three to four weeks."

Help From the Outside

About a week later, two weeks into his detention, Mr. Vance was allowed to make his first call, to Chicago. He called his fiancée, Diane Schwarz, who told him she had thought he might have died.

"It was very overwhelming," Ms. Schwarz recalls of the 12-minute conversation. "He wasn’t quite sure what was going on, and was kind of turning to me for answers and I was turning to him for the same."

She had already been calling members of Congress, alarmed by his disappearance. So was Mr. Ertel’s mother, and some officials began pressing for answers. "I would appreciate your looking into this matter," Senator Richard J. Durbin of Illinois wrote to a State Department official in early May.

On May 7, the Camp Cropper detention board met again, without either man present, and determined that Mr. Ertel was "an innocent civilian," according to the spokeswoman for detention operations. It took authorities 18 more days to release him.

Mr. Vance’s situation was more complicated. On June 17, Lt. Col. Keir-Kevin Curry, a spokesman for the American military’s detention unit, Task Force 134, wrote to tell Ms. Schwarz that Mr. Vance was still being held. "The detainee board reviewed his case and recommended he remain interned," he wrote. "Multi-National Force-Iraq approved the board’s recommendation to continue internment. Therefore, Mr. Vance continues to be a security detainee. We are not processing him for release. His case remains under investigation and there is no set timetable for completion." Over the following weeks, Mr. Vance said he made numerous written requests — for a lawyer, for blankets, for paper to write letters home. Mr. Vance said that he wrote 10 letters to Ms. Schwarz, but that only one made it to Chicago. Dated July 17, it was delivered late last month by the Red Cross.

"Diana, start talking, sending e-mail and letters and faxes to the alderman, mayor, governor, congressman, senators, Red Cross, Amnesty International, A.C.L.U., Vatican, and other Christian-based organizations. Everyone!" he wrote. "I am missing you so much, and am so depressed it’s a daily struggle here. My life is in your hands. Please don’t get discouraged. Don’t take ‘No’ for answers. Keep working. I have to tell myself these things every day, but I can’t do anything from a cell."

The military has never explained why it continued to consider Mr. Vance a security threat, except to say that officials decided to release him after further review of his case.

"Treating an American citizen in this fashion would have been unimaginable before 9/11," said Mike Kanovitz, a Chicago lawyer representing Mr. Vance.

On July 20, Mr. Vance wrote in his notes: "Told ‘Leaving Today.’ Took shower and shaved, saw doctor, got civ clothes back and passport."

On his way out, Mr. Vance said: "They asked me if I was intending to write a book, would I talk to the press, would I be thinking of getting an attorney. I took it as, ‘Shut up, don’t talk about this place,’ and I kept saying, ‘No sir, I want to go home.’ "