WASHINGTON — Flayed by lawmakers’ criticism, Army leaders said yesterday that they accept responsibility for substandard conditions at the service’s flagship Walter Reed Army Medical Center but also said they hadn’t known about most of the problems.

Democrats and Republicans alike suggested the failings go far beyond the one hospital for wounded soldiers in Washington, and they demanded action. Military leaders — and Vice President Cheney — promised they’d get it.

“We can’t fail one of these soldiers or their families, not one. And we did,” said Major General George Weightman, who was in charge of Walter Reed from August 2006 until he was fired last week. He added, “We did not fully recognize the frustrating bureaucratic and administrative processes some of these soldiers go through. We should have, and in this, I failed.”

General Weightman’s comments were echoed by other top Army officials at an emotional House hearing held at the hospital itself as Congress began digging into the controversy.

In a session that mixed contrition and clashes, lawmakers said dilapidated housing and excessive red tape were problems beyond Walter Reed, underscoring how recent new information about the hospital has become a metaphor for broader concerns about the government’s treatment of soldiers returning from wars in Iraq and Afghanistan.

“I’m afraid this is just the tip of the iceberg, that when we got out into the field we may find more of this,” said Rep. Tom Davis, a Republican of Virginia and member of the House Oversight and Government Reform subcommittee, which held the session.

“My question is, where have you been?” Rep. John Tierney, a Democrat of Massachusetts and chairman of the panel, asked Army Undersecretary Peter Geren, Army Chief of Staff General Peter Schoomaker, and Vice Chief General Richard Cody.

In one exchange, General Schoomaker told Mr. Tierney, “I’ve got a daughter and a son-in-law that are on the way to combat. This is not something about people who don’t care. And I am not going to sit here and have anybody tell me that we don’t care about.”

“Nobody said anything about people not caring, so we’ll put that red herring aside and, if I can, calm you down and get you back to the issue here,” Mr. Tierney answered.

Addressing war veterans yesterday, Mr. Cheney promised that the problems at Walter Reed would be fixed.

“There will be no excuses — only action,” Mr. Cheney told a gathering of the Veterans of Foreign Wars.

Separately, as the Bush administration tried to contain political damage from the controversy, Veterans Affairs Secretary James Nicholson said his office would hire 100 new patient advocates, speed benefit claims, and improve medical screenings for veterans at its facilities.

“Our goal is to do things that serve the veterans in the manner that they deserve the best way that we can,” Mr. Nicholson said in an interview on NPR’s “All Things Considered.”

A big question for lawmakers was what Army officials knew about the problems before a series of articles last month by the Washington Post shined a spotlight on them and whether they chose to ignore them.

In addition to General Weightman’s resignation, Defense Secretary Gates forced Army Secretary Francis Harvey to step down last Friday. In addition, Mr. Gates replaced Lieutenant General Kevin Kiley, who was named interim commander of Walter Reed, which he had led between 2000 and 2004, when he became Army surgeon general.