Now Washington is asking him to button it, raising questions about just how far the military should go in pressing its view.
On Monday, Defense Secretary Robert Gates said civilian and military advisers should keep their advice private.
"In this process it is imperative that all of us taking part in these deliberation – civilian and military alike – provide our best advice to the president, candidly but privately," Mr. Gates said at a speech before an Army convention in Washington.
The administration is deep in an intense debate over the merits of sending as many as 40,000 additional troops to Afghanistan to halt deteriorating security. To some experts, the Obama administration's review is the right thing – having a robust internal debate before making a major decision. To others, President Obama is trying to have it both ways – encouraging the military to speak up when it suits his foreign policy objectives but quieting them when it doesn't.
"People are finding themselves wishing that generals were seen and not heard," says one retired senior officer.
McChrystal last week told an audience in London that changing the strategy in Afghanistan from the troop-heavy prospect of building a state that can resist Al Qaeda to the narrower, less troop-intensive approach of targeting terrorists is "probably ... short-sighted."
The Constitution clearly states that military officers operate under civilian control. But does this amount to a gag order? Maybe so, says one expert.
McChrystal should never have appeared at the London speech to begin with, says Larry Korb, a former senior Pentagon official under President Reagan and now an analyst at the Center for American Progress in Washington. [Editor's note: The original version misidentified the president Mr. Korb worked for.]
"When he went, he should never have answered the question," he says. "It was a violation of civilian control of the military."
"To me, that is a firing offense, getting involved right before an election," Korb says.
That seems like a double standard to others. During last year's political campaign, Democrats criticized the Bush administration for not allowing the military to speak up. As a senator, Vice President Joe Biden chastised the Pentagon for not being frank about Iraq or Afghanistan.
Now, Democrats in the administration are leaning on the military to keep quiet.
"What Gates is saying is, it's OK for [military commanders] to speak, so long as they do agree," says the retired senior officer, who would speak on a sensitive political matter only if he was given anonymity.
"McChrystal has given thoughtful answers to reasonable questions," the officer says. "I don't think he has gotten into the realm of policy... The problem is the administration is really uncomfortable with this because the pressure it puts on them."
Yet military officials can also be criticized for acquiescing too meekly. Gen. Peter Pace, the chairman of the Joint Chiefs of Staff under former Defense Secretary Donald Rumsfeld, was pilloried for not standing up to his boss over Iraq.
Military commanders must always be truthful, but they must be careful.
At the Pentagon, military officials say the perception that the uniformed military is trying to influence policy is "regrettable" – and unintended.
"We do understand the perception that these public comments have engendered," says one senior military official who would speak on condition of anonymity. "The military leadership regrets that that is the perception; but by no means is it a deliberate effort."
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