But those documents, and others that were finally unsealed Monday, are at best inconclusive -- attesting that captured terrorism suspects provided crucial intelligence on Al Qaeda and its plans, but offering little to support the argument that harsh or abusive methods played a key role.
The memos and a long-secret CIA inspector general report released the same day fill in details about the agency's embrace of harsh methods to get prisoners to talk. But they do not resolve a question that now seems likely to follow the Bush administration into the history books: Was it necessary to push moral and legal limits of detainee treatment to safeguard the country?
President Obama has insisted the answer is no. He set up a task force in January to examine interrogation options, but the panel steered clear of considering the inclusion of so-called enhanced techniques.
The president this week endorsed a task force recommendation to create an elite interrogation unit -- drawing on experts from throughout the government, not just the CIA -- that will abide by U.S. military guidelines when questioning terrorism suspects.
Cheney again lashed out at the Obama administration and refused to back away from his assertion that harsh interrogation methods worked.
The newly released documents "clearly demonstrate that the individuals subjected to enhanced interrogation techniques provided the bulk of the intelligence we gained about Al Qaeda," he said Monday night in a statement released by his office.
Obama's decision to allow the Justice Department to open a criminal probe of interrogators' conduct, and move authority for questioning prisoners away from the CIA, "serves as a reminder, if any were needed, of why so many Americans have doubts about this administration's ability to be responsible for our nation's security," Cheney said.
Responding to the criticism, an Obama administration official involved with the task force noted that the Bush administration itself had banned the most severe CIA methods years ago. The official was not authorized to speak publicly.
"Cheney seems to be the only one out there who wants to defend waterboarding as a lawful technique," the official said.
The CIA inspector general report is likely to provide ammunition to people on both sides of the argument. In one section, it suggests that the number of intelligence reports soared when waterboarding was used on two high-ranking Al Qaeda captives, Abu Zubaydah and Khalid Shaikh Mohammed.
Mohammed "provided only a few intelligence reports prior to the use of the waterboard, and analysis of that information revealed that much of it was outdated, inaccurate or incomplete," the report says.
It goes on to note that Mohammed was then waterboarded 183 times in March 2003; the rest of the paragraph, which presumably discusses the results, remains censored.
In its top conclusion, the report says the interrogation program had provided intelligence "that has enabled the identification and apprehension of other terrorists and warned of terrorist plots planned for the United States."
But without the ability to isolate the many variables involved in getting such information, the report says, the effectiveness of specific techniques "cannot be so easily measured."
In an interview Tuesday, the author of the CIA report, former Inspector General John L. Helgerson, said, "You could not in good conscience reach a definitive conclusion about whether any specific technique was especially effective, or [whether] the enhanced techniques in the aggregate really worked."
The memos that Cheney urged be declassified are also inconclusive. The title of one indicates how it caught the former vice president's eye: "Detainee Reporting Pivotal for the War Against Al Qaeda."
But the contents say more about the complexity of getting accurate intelligence from prisoners than the reliability of coercion in getting them to talk. A report on Mohammed describes how interrogators took advantage of his mistaken belief that others had already spilled important secrets.
Interrogators confirmed some information with data found on computers, and parlayed tips into arrests that then armed them with new information with which to confront Mohammed, or "KSM."
Details on the number of reports generated from Mohammed are blacked out. But "it will take years," the document says, "to determine definitively all the plots in which KSM was involved."
The Obama task force spent seven months looking at the effectiveness of an array of interrogation techniques but did not devote any attention to whether the coercive means that had been used by the CIA actually worked.
An administration official said that was largely because none of the task force members -- who included representatives of the FBI and CIA -- proposed that any of those methods be included in the review.
"One of the first questions asked was if any agency feels there is a technique outside of the U.S. Army Field Manual that ought to be used," said the Obama administration official involved with the task force. "No agency, including the CIA, requested the study of any technique."
Some officials said that was because the preferences of the White House, and the political risks of proposing to go beyond the military manual, were clear.
"The CIA got what it wanted -- a place at the table for its substantive experts -- while avoiding what it didn't want: responsibility for long-term detention," said a U.S. intelligence official familiar with the issue, who also spoke on condition of anonymity. "For this phase of the task force, it was clear that the Army Field Manual would be the standard."
Times staff writer Josh Meyer in Washington contributed to this report.