WASHINGTON>> President Barack Obama sacked his loose-lipped Afghanistan commander today, a seismic shift for the military order in wartime, and chose the familiar, admired — and tightly disciplined — Gen. David Petraeus to replace him. Petraeus, architect of the Iraq war turnaround, was once again to take hands-on leadership of a troubled war effort.

Obama said bluntly that Gen. Stanley McChrystal’s scornful remarks about administration officials represent conduct that "undermines the civilian control of the military that is at the core of our democratic system." He ousted the commander after a face to face meeting in the Oval Office and named Petraeus, the Central Command chief who was McChrystal’s direct boss, to step in.

In a statement expressing praise for McChrystal yet certainty he had to go, Obama said he did not make the decision over any disagreement in policy or "out of any sense of personal insult." Flanked by Vice President Joe Biden, Defense Secretary Robert Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, in the Rose Garden, he said: "War is bigger than any one man or woman, whether a private, a general, or a president."

He urged the Senate to confirm Petraeus swiftly and emphasized the Afghanistan strategy he announced in December was not shifting with McChrystal’s departure.

"This is a change in personnel but it is not a change in policy," Obama said.

Indeed, as Obama was speaking, McChrystal released a statement saying that he resigned out of "a desire to see the mission succeed."

"I strongly support the president’s strategy in Afghanistan," McChrystal said.

Obama hit several grace notes about McChrystal and his service after their Oval Office meeting, saying that he made the decision to sack him "with considerable regret." And yet, he said the job in Afghanistan cannot be done now under McChrystal’s leadership, asserting that the critical remarks from the general and his inner circle in the Rolling Stone magazine article displayed conduct that doesn’t live up to the standards for a command-level officer.

Obama seemed to suggest that McChrystal’s military career is over, saying the nation should be grateful "for his remarkable career in uniform" as if that has drawn to a close.

McChrystal left the White House after the meeting and returned to his military quarters at Washington’s Fort McNair. A senior military official said there is no immediate decision about whether he would retire from the Army, which has been his entire career. The official spoke on condition of anonymity because he was not authorized to speak publicly.

Petraeus, who attended a formal Afghanistan war meeting at the White House on Wednesday, has had overarching responsibility for the wars in both Afghanistan and Iraq as head of Central Command. He was to vacate the Central Command post after his expected confirmation, giving Obama another key opening to fill. The Afghanistan job is actually a step down from his current post but one that filled Obama’s pre-eminent need.

Petraeus is the nation’s best-known military man, having risen to prominence as the commander who turned around the Iraq war in 2007, applying a counterinsurgency strategy that has been adapted for Afghanistan.

He has a reputation for rigorous discipline. He keeps a punishing pace — spending more than 300 days on the road last year. He briefly collapsed during Senate testimony last week, apparently from dehydration. It was a rare glimpse of weakness for a man known as among the military’s most driven.

In the hearing last week, Petraeus told Congress he would recommend delaying the pullout of U.S. forces from Afghanistan beginning in July 2011 if need be, saying security and political conditions in Afghanistan must be ready to handle a U.S. drawdown.

That does not mean Petraeus is opposed to bringing some troops home, and he said repeatedly that he supports Obama’s revamped Afghanistan strategy. Petraeus’ caution is rooted in the fact that the uniformed military — and counterinsurgency specialists in particular — have always been uncomfortable with rigid parameters.

With Washington abuzz, there had been a complete lockdown on information about the morning’s developments until just before Obama spoke. By pairing the decision on McChrystal’s departure with the name of his replacement, Obama is seeking to move on as quickly as possible from the firestorm.

In the magazine article, McChrystal called the period last fall when the president was deciding whether to approve more troops "painful" and said the president appeared ready to hand him an "unsellable" position. McChrystal also said he was "betrayed" by Ambassador Karl Eikenberry, the man the White House chose to be his diplomatic partner in Afghanistan.

He accused Eikenberry of raising doubts about Karzai only to give himself cover in case the U.S. effort failed. "Now, if we fail, they can say ‘I told you so,"’ McChrystal told the magazine. And he was quoted mocking Vice President Joe Biden.

If not insubordination, the remarks — as well as even sharper commentary about Obama and his White House from several in McChrystal’s inner circle — were at the least an extraordinary challenge from a military leader. The capital hadn’t seen a similar public contretemps between a president and a top wartime commander since Harry Truman stripped Gen. Douglas MacArthur of his command more than a half-century ago after disagreements over Korean war strategy.

Notably, neither McChrystal nor his team questioned the accuracy of the story or the quotes in it. McChrystal issued an apology.

Despite McChrystal’s military achievements, he has a history of making waves and this was not his first brush with Obama’s anger. Last fall as Obama was weighing how to adjust Afghanistan policy, McChrystal spoke bluntly and publicly about his desire for more troops — earning a scolding from the president, who felt the general was trying to box him into a corner.

Waheed Omar, spokesman for Afghan President Hamid Karzai, said Petraeus "will also be a trusted partner." Karzai had been a lonely voice in speaking out in support of McChrystal. But Omar said of Petraeus: "He is the most informed person and the most obvious choice for this job."

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Associated Press writers Julie Pace, Pauline Jelinek, Kimberly Dozier and Anne Flaherty in Washington and Deb Riechmann in Kabul, Afghanistan, contributed to this report.