WASHINGTON – A congressional hearing that lawmakers called the most important of the year opened like a rock concert today, with crackling anticipation and screeching feedback from the acoustic speakers. Yet this show turned out to be David Petraeus, unplugged.

Calm, measured, unflinching, the Iraq war commander walked lawmakers through the latest turns in the unpopular war, stopping well short of promising victory but asking the nation to give escalation a chance.

Even Democrats who despise the war policy were deferential in the face of the general’s even-keeled demeanor and his shiny silver stars, four to a shoulder. “He’s one of the best,” Rep. Ike Skelton of Missouri, who ran proceedings, said.

In his Army green, under sparkling chandeliers, General Petraeus presented statistics on conditions in Iraq that leaped off the page like fever charts on a hospital bed, indicating the patient was terribly ill but might be coming around. He declared “it is possible to achieve our objectives in Iraq over time.”

At the moment of highest anticipation — when General Petraeus was finally asked to speak, after lengthy opening statements from lawmakers — his microphone failed. In the awkward minutes that followed, two more protesters made a commotion and were removed from the room.

The hearing had to recess because of the technical glitch. “Test, test,” someone said through the mike. The acoustic speakers cried foul. After 10 minutes, all was fixed and the show went on.

A protester who called Iraqis “beautiful people” and accused General Petraeus of lying was quickly removed during his remarks. Other discordant voices were similarly silenced before he began. Before the general spoke, the anti-war activist, Cindy Sheehan, was among those arrested for shouting in the room.

Democrats were careful to exempt the general from their contempt of President Bush’s course.

“This is not a knock on you,” Rep. Tom Lantos, Democrat of California, told General Petraeus and the ambassador to Iraq, Ryan Crocker. But he said they had come to Congress to “restore credibility to a discredited policy.”

“With all respect to you,” he went on, “I don’t buy it.”

As soon as General Petraeus finished, three more protesters shouted from the back and were ejected. One of them, a woman wearing a cardboard crown saying “Pull Out,” screamed “No, no, no!” as security guards took her arms and tugged her out of the room. Yet another followed as Mr. Crocker began his remarks.

An exasperated Mr. Skelton said protesters who disrupted proceedings would be prosecuted.

“There will be no disturbances,” he vowed, after half a dozen had already taken place.

There was tension, too, among the lawmakers. Republicans objected to an ad taken out by MoveOn.org that accused General Petraeus of “cooking the books for the White House,” and they demanded that Democrats disassociate themselves from the sentiment.

“Nobody has to distance themselves from something they weren’t associated with,” Rep. Neil Abercrombie, Democrat of Hawaii, said

“Take it easy,” Rep. Ileana Ros-Lehtinen, Republican of Florida, said.

Generals command keen attention on Capitol Hill — even William Westmoreland, speaking to a joint session of Congress at the height of the tempest over Vietnam, was interrupted 19 times for applause in a half-hour speech in 1967.

President Johnson attributed much of the anti-war sentiment to partisan objections to him and felt there was a positive story to be told about Vietnam.

Westmoreland stepped forward with his “light-at-the-end-of-the-tunnel talks” to members of Congress and the press, a political scientist at Ohio State, John Mueller, said. But as it turned out, he added, “the tunnel was very long.”