WASHINGTON >> The United States brutalized scores of terror suspects with interrogation tactics that turned secret CIA prisons into chambers of suffering and did nothing to make America safer after the 9/11 attacks, Senate investigators concluded Tuesday.

The Senate Intelligence Committee’s torture report, years in the making, accused the CIA of misleading its political masters about what it was doing with its “black site” captives and deceiving the nation about the effectiveness of its techniques.

The report was the first public accounting of tactics employed after the Sept. 11, 2001, terrorist attacks, and it described far harsher actions than had been widely known.

Tactics included confinement to small boxes, weeks of sleep deprivation, simulated drowning, slapping and slamming, and threats to kill, harm or sexually abuse families of the captives.

The report produced revulsion among many, challenges to its veracity among some lawmakers and a sharp debate about whether it should have been released at all.

GOP Sen. John McCain, tortured in Vietnam as a prisoner of war, was out of step with some fellow Republicans in welcoming the report and endorsing its findings.

“We gave up much in the expectation that torture would make us safer,” he said in a Senate speech. “Too much.”

Five hundred pages were released, representing the executive summary and conclusions of a still-classified 6,700-page full investigation.

President Barack Obama declared some of the past practices to be “brutal, and as I’ve said before, constituted torture in my mind. And that’s not who we are,” he told the Spanish-language TV network Telemundo in an interview.

Sen. Dianne Feinstein of California, the Democratic committee chairman whose staff prepared the summary, branded the findings a stain on the nation’s history.

“Under any common meaning of the term, CIA detainees were tortured,” she declared, commanding the Senate floor for an extended accounting of the techniques identified in the investigation.

The report catalogued the use of ice baths, death threats, shackling in the cold and much more. Three detainees faced the simulated drowning technique known as waterboarding. Many developed psychological problems.

But the “enhanced interrogation techniques” didn’t produce the results that really mattered, the report asserts in its most controversial conclusion. It cites CIA cables, emails and interview transcripts to rebut the central justification for torture — that it thwarted terror plots and saved American lives.

In a statement, CIA Director John Brennan said the agency made mistakes and has learned from them.

But he also asserted the coercive techniques “did produce intelligence that helped thwart attack plans, capture terrorists and save lives.”

George Tenet, who was CIA director at the time, said in an interview: “We know that the program led to the capture of al-Qaida leaders and took them off the battlefield, that it prevented mass casualty attacks and that it saved thousands of American lives.”

Top Republicans, including Senate GOP leader Mitch McConnell of Kentucky, agreed. But not Democrat Harry Reid of Nevada, the Senate majority leader. He said, “It got us nothing except a bad name.”

The report, released after months of negotiations with the administration about what should be censored, was issued as U.S. embassies and military sites worldwide fortified security in case of an anti-American backlash.

Earlier this year, Feinstein accused the CIA of infiltrating Senate computer systems in a dispute over documents as relations between the investigators and the spy agency deteriorated, the issue still sensitive years after Obama ordered a halt to any such interrogation practices upon taking office.

President George W. Bush approved the program through a covert finding in 2002, but he wasn’t briefed by the CIA about the details until 2006. At that time Bush expressed discomfort with the “image of a detainee, chained to the ceiling, clothed in a diaper and forced to go to the bathroom on himself.”

After al-Qaida operative Abu Zubaydah was arrested in Pakistan in 2002, the CIA received permission to use waterboarding, sleep deprivation, close confinement and other techniques. Agency officials added unauthorized methods, the report says.

At least five men in CIA detention received “rectal rehydration,” a form of feeding through the rectum. The report found no medical necessity for the treatment.

At least three in captivity were told their families would suffer, with CIA officers threatening to harm their children, sexually abuse the mother of one man, and cut the throat of another man’s mother.

Zubaydah was held in a secret facility in Thailand, called “detention Site Green” in the report. Early on, with CIA officials believing he had information on an imminent plot, Zubaydah was left isolated for 47 days without questioning, the report says. Later, he was subjected to the panoply of techniques. He later suffered mental problems.

He wasn’t alone. In September 2002, at a facility referred to as COBALT– the CIA’s “Salt Pit” in Afghanistan — detainees were kept isolated and in darkness. Their cells had only a bucket for human waste.

Redha al-Najar, a former Osama bin Laden bodyguard, was the first prisoner there. CIA interrogators found that after a month of sleep deprivation, he was a “broken man.” But the treatment got worse, with officials lowering food rations, shackling him in the cold and giving him a diaper instead of toilet access.

Gul Rahman, a suspected extremist, received enhanced interrogation there in late 2002, shackled to a wall in his cell and forced to rest on a bare concrete floor in only a sweatshirt. The next day he was dead. A CIA review and autopsy found he died of hypothermia.

Justice Department investigations into that and another death of a CIA detainee resulted in no charges.

During one waterboarding session, Zubaydah became “completely unresponsive with bubbles rising through his open full mouth,” according to internal CIA records.

Khalid Sheikh Mohammed, the 9/11 mastermind, received the waterboarding treatment 183 times. At one point, he was waterboarded for not confirming a “nuclear suitcase” plot the CIA later deemed a scam. Another time, his waterboarding produced a fabricated confession about recruiting black Muslims in Montana.

After reviewing 6 million agency documents, investigators said they could find no example of unique, life-saving intelligence gleaned from coercive techniques — another sweeping conclusion that the CIA and Republicans contest.

The report claims to debunk the CIA’s assertion its practices led to bin Laden’s killing. The agency says its interrogation of detainee Ammar al-Baluchi revealed a known courier was taking messages to and from bin Laden.

A special United Nations human rights and counterterrorism official said CIA officers and other U.S. government officials should be prosecuted.

“The fact that the policies revealed in this report were authorized at a high level within the U.S. government provides no excuse whatsoever,” Ben Emmerson said in a statement.