A 30-page report by Human Rights Watch describes an Army captain's 17-month effort to gain clear understanding of how U.S. soldiers were supposed to treat detainees, and depicts his frustration with what he saw as widespread abuse that the military's leadership failed to address. The Army officer made clear that he believes low-ranking soldiers have been held responsible for abuse to cover for officers who condoned it.

The report does not identify the two sergeants and a captain who gave the accounts, although Capt. Ian Fishback has presented some of his allegations in a letter to Sen. John McCain (R-Ariz.).

Their statements included vivid allegations of violence against detainees held at Forward Operating Base Mercury, outside Fallujah, shortly before the notorious abuse at the Abu Ghraib prison began. The soldiers described incidents similar to those reported in other parts of Iraq -- such as putting detainees in stress positions, exercising them to the point of total exhaustion, and sleep deprivation.

"Some days we would just get bored so we would have everyone sit in a corner and then make them get in a pyramid," an unidentified sergeant who worked at the base from August 2003 to April 2004 told Human Rights Watch. "This was before Abu Ghraib but just like it. We did that for amusement."

In addition to talking to Human Rights Watch, Fishback has made his concerns known in a series of signed letters and memos sent to Capitol Hill. Fishback, a West Point graduate who has served in Afghanistan and Iraq, wrote that no one in his chain of command has been able to give him a clear explanation of what humane treatment is, and he believes that US soldiers have regularly violated the Geneva Conventions by torturing detainees and taking family members hostage as a means of coercion.

"Despite my efforts, I have been unable to get clear, consistent answers from my leadership about what constitutes lawful and humane treatment of detainees," Fishback wrote in a Sept. 16 letter to McCain, a member of the Armed Services Committee and a former prisoner of war in Vietnam. "I am certain that this confusion contributed to a wide range of abuses including death threats, beatings, broken bones, murder, exposure to elements, extreme forced physical exertion, hostage-taking, stripping, sleep deprivation and degrading treatment." Fishback, reached by telephone yesterday, declined to comment.