Newly released U.S. Defence Department documents and memos about the first years of operation of the jail at the U.S. Guantanamo Bay Naval Base in Cuba portray a chaotic and sometimes violent operation that its own commanders described as dysfunctional.

The documents were turned over to the American Civil Liberties Union as part of a Freedom of Information Act lawsuit.

One of the newly released documents from 2005 is the statement of one of the first commanders of Guantanamo to another general who was investigating allegations of prisoner abuse lodged by the FBI.

The now retired Maj. Gen. Michael Dunleavy commanded the Guantanamo interrogation operation in 2002.

Dunleavy described the chaos he found when he arrived: a lack of security and control over detainees who would riot and throw food and turned items like spoons, magnets and welding rods into weapons.

He said his interrogators were virtually inexperienced and the military linguists "were worthless."

He said he was brought in to bring "a commonsense way on how to do business." Dunleavy had experience with more than 3,000 interrogations going back 35 years.

Dunleavy also complained about FBI officials who went to Guantanamo every two weeks and "could not decide what to do" and never built up a rapport.

"The mission was to get intelligence to prevent another 9/11," Dunleavy said.

He said physical torture would not produce intelligence, but instead they needed to build rapport and create a "dependency relationship" with prayer beads and the Qur'an. He said he treated detainees "as human beings, but not like soldiers" and denied there was any torture.

But he said one interrogator had to be removed after he "physically mishandled" a detainee, belting and handcuffing him to an eyebolt on the floor. An FBI agent was removed after "he went across the desk at a detainee" after the detainee threatened to kill his family.

He said his "best interrogator" was prosecuted and another officer was removed after it became apparent he was an alcoholic who secretly drank in his room every night.

He said loud music and yelling were used to disrupt detainees' thought processes. He said chaining a detainee in a fetal position was "not a normal procedure" but may have been used to secure a prisoner who leapt at an interrogator.

Maj. Gen. Geoffrey Miller, who commanded Guantanamo from late 2002 to March 2004, said in another newly released document that he had rejected a proposal to use the harsh techniques employed by survival trainers to prepare American troops for combat. He said some of the techniques "went beyond what I felt comfortable with."

Some of the same harsh techniques had already been secretly adopted by the CIA with White House approval.

Another set of memos, dated 2004, describe how a detainee was knocked unconscious for several minutes by guards while he was being forcibly removed from his cell.

The memos were apparently written in response to State Department inquiries about a prisoner's treatment at the military-run jail.