He finds plenty of blame for others in the Bush administration and the military, but he also concedes he fell short or was just plain wrong on a few fronts.
He writes, for example, of mild regret that he did not stop L. Paul Bremer, the chief administrator of Iraq in the early months of the war, from ordering the entire Iraqi army disbanded - a move that ran counter to recommendations that flowed from a series of military analyses earlier in the year.
Rumsfeld says he had concluded that the benefits of disbanding the army - as part of a U.S. drive to wipe out Baathist influence in Iraq following the overthrow of Saddam Hussein - outweighed the risks. In hindsight, many critics believe that Bremer's decision was one of the costliest mistakes of the war. On paper, Bremer worked for Rumsfeld, but in practice Bremer answered more regularly and directly to the White House.
A formerly secret memo from a senior Rumsfeld staff official, declassified at Rumsfeld's request as part of a trove of papers posted Monday to his website (http://www.rumsfeld.com), says Bremer informed Rumsfeld on May 19, 2003, that he intended to issue an order dissolving the Iraqi military. Bremer signed the order four days later.
"I was told of Bremer's decision," Rumsfeld wrote in his memoir, "and possibly could have stopped it."
Rumsfeld also conceded an inch or two on charges that he and others in the administration overstated the certainty of their claims that Saddam had weapons of mass destruction. He recalls his remark just days after the war began about the location of weapons of mass destruction stockpiles inside Iraq. "We know where they are," Rumsfeld told a television interviewer. "They're in the area around Tikrit and Baghdad."
In his book, he denied that he or any other administration official lied about WMD. "While I made a few misstatements - in particular the one mentioned above - they were not common and certainly not characteristic."
Rumsfeld revealed in his book that he urged a U.S. military strike on a suspected chemical weapons site in northern Iraq in 2003 and that he wanted the attack to coincide with Secretary of State Colin Powell's address to the U.N. Security Council making the case for war.
In his memoir, "Known and Unknown," Rumsfeld wrote that the Joint Chiefs supported a strike, based on what Rumsfeld called extensive but not conclusive CIA evidence that the site housed an underground facility for testing chemical weapons. He called it a "fairly sizeable terrorist operation."
The prewar attack never happened, although the site was struck in the opening days of the war that President George W. Bush launched in March 2003, about six weeks after Powell's U.N. speech. The U.S. never found substantial evidence of an active Iraqi program to produce weapons of mass destruction, but Rumsfeld believed that the site near the Iranian border presented the best chance to prove they existed before the war began.
"For whatever reason, the administration never made public these facts about an active WMD production facility run by terrorists in Iraq," Rumsfeld wrote.
He said he made his recommendation to Bush at a National Security Council meeting Feb. 3, 2003, in which Powell sketched out the presentation he was to make at the U.N. two days later.
Rumsfeld quotes himself as telling the meeting, "We should hit Khurmal during the speech, given that Colin will talk about it." Khurmal is the name of a village near the site. Powell objected.
In his U.N. presentation, Powell described it as "Terrorist Poison and Explosive Factory, Khurmal." Rumsfeld said Khurmal was operated by Ansar al-Islam, a Sunni militant group with ties to Abu Musab al-Zarqawi, a Jordanian extremist who later led the Iraq branch of the al-Qaida terrorist network.
Rumsfeld wrote that he wanted to attack the site before Powell finished his presentation in New York because otherwise the site would be abandoned.
Had Powell not stood in the way, in Rumsfeld's view, the Bush administration might have gained conclusive evidence that Iraq had an active WMD site. "As expected, shortly after Powell's speech was delivered, many of the terrorists fled Khurmal," he wrote.
An Associated Press reporter who visited the site a few days after Powell's speech found a half-built cinderblock compound filled with heavily armed Kurdish men, video equipment and children - but no obvious sign of chemical weapons manufacturing. Much of the site was destroyed by American cruise missile strikes at the outset of the invasion.
Micah Zenko, a political scientist at the Council on Foreign Relations, extensively researched U.S. planning for a military strike on Khurmal in 2002 and detailed it in his book "Between Threats and War." He said in an interview that he was unaware that Rumsfeld had advocated bombing the place while Powell was at the U.N.
By that time, the Khurmal camp had been largely empty for months, Zenko said.
The Rumsfeld memoir covers the full span of his 78 years, including growing up in a small town outside Chicago, his Navy days, his years in Congress, a string of staff jobs in the Nixon White House, his first tour as defense secretary under President Gerald R. Ford, a period as a business executive and his return to the Pentagon in January 2001. He is the only person to have served twice as defense secretary; he also was the youngest to have held the job and the oldest.