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WASHINGTON -- If the memoir of Donald Rumsfeld, among the most powerful and controversial U.S. secretaries of defense, catches on with readers and critics, he could cite one of his many "Rumsfeld's Rules":

"The harder I work, the luckier I am."

When Rumsfeld began thinking about his book, "Known and Unknown," he imagined a more typical Washington release: a quick, impressionistic story based on whatever he recalled.

Instead, he and a team of six aides worked four years on what became a 700-page narrative, with an additional 100-plus pages of end notes. Dozens of books were consulted and thousands of documents reviewed, from White House memos to letters Rumsfeld's parents wrote to each other during World War II. Rumsfeld's sister Joan and former Secretary of State George Shultz were among the friends, family members and colleagues who came to Washington for conversations.

"I started thinking about this amazing archive I had," he said during a recent interview. "The fact that I had it persuaded me that I ought to take advantage of it."

Rumsfeld is seated in a conference room at his office suite, where the walls document a long, high-level life of politics and history: a photograph of then-Rep. Rumsfeld with President Lyndon Johnson in the 1960s; a signed copy of President Gerald Ford's swearing-in statement in 1974; a piece of shrapnel from the hijacked plane that struck the Pentagon on Sept. 11, 2001.

At 78, Rumsfeld had enough energy to narrate the audio edition of the book himself -- eight days of recording, eight hours a day. He looks grayer, but otherwise little changed from his time as defense secretary under President George W. Bush, with his rimless glasses and quick, confident grin.

For much of his career in public office, Rumsfeld has been compiling information. As a Republican congressman from Illinois, he kept records on every vote he made and the reason for each decision. He held on to notes from presidential briefings and recorded thoughts and ideas into a Dictaphone.

Rumsfeld has set up a website, www.rumsfeld.com (which goes live on publication day, Feb. 8), that allows visitors to link to the documents he used as source material. During his interview, Rumsfeld showed samples, including eight pages of notes from a briefing Johnson gave in 1966 on the Vietnam War and White House papers from July 1975, when he was chief of staff under President Ford, with passages initialed by Rumsfeld's then-assistant, Dick Cheney.

"It's not a journal, it's not a diary," he says of the Ford White House notes. "It is a set of working documents that I've never edited. In fact, most I've never reread."

As defense secretary under President Bush, Rumsfeld issued thousands of memos; "snowflakes," they were called. He reads from some issued in 2003 and in 2005: "Are we winning or losing the War on Terror?" "Is the U.S. government changing fast enough?" "Do we need more troops? And if so, where and for what purpose?"

"My brain would be going," he says. "I wanted to find out something. I needed help. I needed advice. Some of them were just, 'I need a haircut."'

Another Rumsfeld Rule: "If you are not criticized, you may not be doing much." As defense secretary, he was admired as daring and innovative by foreign policy hawks and others, and was a close ally of Vice President Cheney. But he was deeply disliked by opponents of the Iraq war, and many Democrats and even some former military leaders urged his resignation. He was an architect of the Iraq conflict, whose departure was announced, just after Election Day in 2006, as the war became increasingly unpopular and Republicans lost control of Congress.

Few words during his tenure stood out more than the response Rumsfeld offered in 2002 about the lack of evidence that Iraq was supplying terrorists with weapons of mass destruction.

"Reports that say that something hasn't happened are always interesting to me, because, as we know, there are known knowns; there are things we know that we know," he said. "There are known unknowns. That is to say, there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know."

And so, with a wink, he called his book "Known and Unknown." He explains that his comments have roots in war theory, philosophy and in science. He says the idea of "known knowns" and "unknown unknowns" and so forth came up during intelligence briefings.

"I used the phrase in a Pentagon press conference one day, and that's when it started rolling," Rumsfeld says. "I titled the book that because I believe people will find there are things they didn't know."

He will not discuss specific contents of the book, will not comment on current events (he saves that for his Twitter account, RumsfeldOffice) and had no comment on President Bush's "Decision Points," which he said he's been too busy to read. But he says "Known and Unknown" will take on the most sensitive subjects, from the detainment facility at Guantanamo Bay, Cuba, to the mistreatment of prisoners at Abu Ghraib in Iraq.

"I brought in people who were involved and outside advisers to discuss the legal decisions that were made. And in the book, I present them in a direct way," he says.

In Washington, Rumsfeld was known as a tenacious and effective fighter of policy wars, once described by former Secretary of State Henry Kissinger as a "skilled full-time politician-bureaucrat in whom ambition, ability, and substance fuse seamlessly." In the 1970s, as chief of staff and then defense secretary in the Ford administration, Rumsfeld clashed with Kissinger, with Rumsfeld opposing, and helping to prevent, by many accounts, an arms control deal Kissinger had been trying to negotiate with the then Soviet Union. During the Bush administration, Rumsfeld was at odds with Secretary of State Colin Powell about Iraq.

The differences were not personal, Rumsfeld says. He recalls receiving a book that Kissinger had written, with the inscription, "To an occasional adversary and a permanent friend."

"When I started working on the book, Kissinger said, `You tell it like it was.' We differed on some issues, and there's nothing wrong with that. It was professional and healthy," Rumsfeld says.

Working on the book meant second-guessing his memory. In 1983, Rumsfeld was a special Middle East envoy for President Ronald Reagan and met with Iraqi leader Saddam Hussein, at the time viewed as a buffer against Iran. Some years ago, Rumsfeld was told of a magazine article that said he had personally delivered a letter from Reagan. Rumsfeld had no memory of doing so, but it turns out a State Department cable exists in which Saddam thanked Rumsfeld for the message.

The letter must have come from the State Department itself, Rumsfeld says.

"How could anyone believe that you couldn't remember if you delivered a letter from President Reagan to Saddam Hussein?" he says. "That's the kind of thing that persuaded me to take my time and look at the documents, since I had so many of them."