The sharp-tongued architect of the war in Iraq resigned one day after midterm elections in which the execution of the war had become one of the key issues.
His resignation will not be effective immediately. He'll continue in his post until his replacement is confirmed by the Senate.
Rumsfeld's tenure at the Pentagon is not without achievement. By next month, he will become the longest-serving Secretary of Defense in the history of the nation. As President Bush pointed out during a news conference on Wednesday, Rumsfeld worked to save lives at the Pentagon in the immediate aftermath of the September 11 attacks. He also planned the successful and unconventional attack on Afghanistan in response to those attacks.
But the 74-year-old Rumsfeld had become a prominent target for Democrats, a growing number of Republicans and some former generals who have lost confidence in the U.S. policy in Iraq.
Rumsfeld's public image was hurt by comments he made about the war that ended up being untrue.
Rumsfeld tried to downplay the looting and civil unrest in Iraq after Saddam's regime had fallen in April 2003. In a televised briefing from the Pentagon, he said the media was misusing the scenes of chaos being broadcast from Baghdad to the rest of the world.
"The images you are seeing on television," he said. "You are seeing it over and over and over, and it's the same picture, of some person walking out of some building with a vase. And you see it 20 times. And you think, 'My goodness, were there that many vases?'"
It later became obvious that the looting and destruction of both artifacts and records in Iraq was widespread and caused many problems for the redevelopment and security of the country.
He also infuriated his critics with flippant quips, which were often seen as arrogant, reports CBS News correspondent Bob Orr.
In December 2004, while being questioned by troops about the lack of armored Humvees, Rumsfeld replied with the , "As you know, you have to go to war with the Army you have, not the Army you want."
His brusque attitude has also rankled many in the military with his management style and his constant push for modernization and transformation of the armed forces.
In April, a group of retired generals made a the Secretary of Defense.
"He went to war with a flawed plan. He didn't account for the hard work to build the peace after we took down the regime," retired Army Maj. Gen. John Batiste, who served as an infantry division commander in Iraq for 2½ years until last November, said on CBS News' The Early Show at the time.
Rumsfeld was also pilloried by journalist Bob Woodward in his book, "State of Denial." The book claims that Rumsfeld was not only abusive to his military staff and dismissive of other members of the Cabinet, but also that he mismanaged the planning and execution of the war.
Woodward wrote that a top general said Rumsfeld had that the chairman of the Joint Chiefs of Staff has become "the parrot on Rumsfeld's shoulder."
"State of Denial" also claimed that White House Chief of Staff Andy Card and First Lady Laura Bush wanted the president to fire Rumsfeld.
Many of Rumsfeld's colleagues, friends and bosses from his many years in Washington rushed to support him.
Former President Gerald Ford, who appointed Rumsfeld as his Chief of Staff and later made his Secretary of Defense, released a statement and congratulating the current president on his choice.
Mr. Bush "knew that Don, who had been in the job before, was extremely well-suited to take on this challenge and contend with a bureaucracy that has a built-in resistance to change," Mr. Ford's statement said. "The president knew that successfully carrying out these missions, against stiff resistance, takes someone with a certain amount of steel."