Cheney's disappointment with the former president surfaced recently in one of the informal conversations he is holding to discuss the book with authors, diplomats, policy experts and past colleagues. By habit, he listens more than he talks, but Cheney broke form when asked about his regrets.

"In the second term, he felt Bush was moving away from him," said a participant in the recent gathering, describing Cheney's reply. "He said Bush was shackled by the public reaction and the criticism he took. Bush was more malleable to that. The implication was that Bush had gone soft on him, or rather Bush had hardened against Cheney's advice. He'd showed an independence that Cheney didn't see coming. It was clear that Cheney's doctrine was cast-iron strength at all times -- never apologize, never explain -- and Bush moved toward the conciliatory."

The two men maintain respectful ties, speaking on the telephone now and then, though aides to both said they were never quite friends. But there is a sting in Cheney's critique, because he views concessions to public sentiment as moral weakness. After years of praising Bush as a man of resolve, Cheney now intimates that the former president turned out to be more like an ordinary politician in the end.

Cheney's post-White House career is as singular as his vice presidency, a position he transformed into the hub of power. Drained of direct authority and cast aside by much of the public, he is no less urgently focused, friends and family members said, on shaping events.

The former vice president remains convinced of mortal dangers that few other leaders, in his view, face squarely. That fixed belief does much to explain the conduct that so many critics find baffling. He gives no weight, close associates said, to his low approval ratings, to the tradition of statesmanlike White House exits or to the grumbling of Republicans about his effect on the party brand.

John P. Hannah, Cheney's second-term national security adviser, said the former vice president is driven, now as before, by the nightmare of a hostile state acquiring nuclear weapons and passing them to terrorists. Aaron Friedberg, another of Cheney's foreign policy advisers, said Cheney believes "that many people find it very difficult to hold that idea in their head, really, and conjure with it, and see what it implies."

What is new, Hannah said, is Cheney's readiness to acknowledge "doubts about the main channels of American policy during the last few years," a period encompassing most of Bush's second term. "These are not small issues," Hannah said. "They cut to the very core of who Cheney is," and "he really feels he has an obligation" to save the country from danger.

Cheney's imprint on law and policy, achieved during the first term at the peak of his influence, had faded considerably by the time he and Bush left office. Bush halted the waterboarding of accused terrorists, closed secret CIA prisons, sought congressional blessing for domestic surveillance, and reached out diplomatically to Iran and North Korea, which Cheney believed to be ripe for "regime change."

Some of the disputes between the president and his Number Two were more personal. Shortly after Bush fired Donald H. Rumsfeld, Cheney called his old mentor history's "finest secretary of defense" and invited direct comparison to Bush by saying he had "never learned more" from a boss than he had as Rumsfeld's deputy in the Ford administration.

The depths of Cheney's distress about another close friend, his former chief of staff and alter ego I. Lewis "Scooter" Libby, have only recently become clear. Bush refused a pardon after Libby's felony convictions in 2007 for perjury and obstruction of an investigation of the leak of a clandestine CIA officer's identity. Cheney tried mightily to prevent Libby's fall, scrawling in a note made public at trial that he would not let anyone "sacrifice the guy that was asked to stick his neck in the meat grinder." Cheney never explained the allusion, but grand jury transcripts -- and independent counsel Patrick J. Fitzgerald -- suggested that Libby's false statements aimed above all to protect the vice president.

Last month, an account in Time magazine, based on close access to Bush's personal lawyer and White House counsel, described Cheney's desperate end-of-term efforts to change Bush's mind about a pardon. Cheney, who has spent a professional lifetime ignoring unflattering stories, issued a quietly furious reply. In the most explicit terms, he accused Bush of abandoning "an innocent man" who had served the president with honor and then become the "victim of a severe miscarriage of justice." Cheney now says privately that his memoir, expected to be published in spring 2011, will describe their heated arguments in full.

Despite an ailing heart and reduced mobility, the former vice president at age 68 retains a prodigious capacity for work. He rises early, reads voraciously about history and current events, and acquired a BlackBerry in modest recompense for the loss of daily intelligence briefings. He allows himself some indulgences, Liz Cheney said in an interview. She said her father relishes his new freedom to take a morning drive to Starbucks in a black SUV, toting home the decaffeinated latte on which his doctor and his wife, Lynne, insist. He attends the soccer and softball games of his oldest grandchildren, Kate and Elizabeth, and spends more time than he could as vice president fly fishing near his vacation homes in Wyoming and on Maryland's Eastern Shore.

But Cheney passes most of his days at the top of the garage at his new house in McLean, where he built an office under the dormered roof and filled it with books and binders of his vice presidential papers. He kept copies of the unclassified ones and consults the rest on visits to the National Archives. He took detailed notes in the White House, head bobbing up and down as he wrote and sometimes disappearing from the screen in videoconferences. Those notes, according to one person who has discussed them with Cheney, will form the core of his account of the Bush years.

"What impressed me was his continuing zeal," said an associate who discussed the book with Cheney. "He hadn't stepped back a bit from the positions he took in office to a more relaxed, Olympian view. He was still very much in the fray. He's not going to soften anything or accommodate shifts of conscience. There was no sense in which he looked back and said, 'I wish I'd done something differently.' Rather, there was a sense that they hadn't gone far enough. If he'd been equipped with a group of people as ideologically rigorous as he was, they'd have been able to push further."

Some old associates see Cheney's newfound openness as a breach of principle. For decades, he expressed contempt for departing officials who wrote insider accounts, arguing that candid internal debate was impossible if the president and his advisers could not count on secrecy. As far back as 1979, one of the heroes in Lynne Cheney's novel "Executive Privilege" resolved never to write a memoir because "a president deserved at least one person around him whose silence he could depend on." Cheney lived that vow for the next 30 years.

As vice president, according to one witness, Cheney "was livid" when the memoir of L. Paul Bremer, who led the occupation of Iraq, made the less-than-stunning disclosure that Cheney shared Bremer's concern about U.S. military strategy. A Cabinet-level Bush appointee recalled that Cheney likewise described revelations by former Treasury secretary Paul H. O'Neill and former White House spokesman Scott McClellan as "beyond the pale."

"If he goes out and writes a memoir that spills beans about what took place behind closed doors, that would be out of character," said Ari Fleischer, who served as White House spokesman during Bush's first term.

Yet that appears to be precisely Cheney's intent. Robert Barnett, who negotiated Cheney's book contract, passed word to potential publishers that the memoir would be packed with news, and Cheney himself has said, without explanation, that "the statute of limitations has expired" on many of his secrets. "When the president made decisions that I didn't agree with, I still supported him and didn't go out and undercut him," Cheney said, according to Stephen Hayes, his authorized biographer. "Now we're talking about after we've left office. I have strong feelings about what happened. . . . And I don't have any reason not to forthrightly express those views."

Liz Cheney, whom friends credit with talking her father into writing the book, described the memoir as a record for posterity. "You have to think about his love of history, and when he thinks about this memoir, he thinks about it as a book his grandchildren will read," she said.

What the former vice president assuredly will not do, according to friends and family, is break a lifetime's reticence about his feelings. Alluding to Bush's forthcoming memoir, Cheney told one small group recently that he had no interest "in sharing personal details," as the former president planned to do.

"He sort of spat the word 'personal,' " said one person in the room.