WASHINGTON — Flayed by lawmakers’ criticism, Army leaders said Monday 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 Dick Cheney — promised they’d get it.

“We can’t fail one of these soldiers or their families, not one. And we did,” said Maj. Gen. George W. Weightman, in charge of Walter Reed from August 2006 until he was fired last week. “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.”

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

“My question is, where have you been?” Rep. John Tierney, D-Mass., chairman of the panel, asked Army Undersecretary Peter Geren, Army Chief of Staff Gen. Peter Schoomaker and Vice Chief Gen. Richard Cody.

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

“There will be no excuses — only action,” Cheney told a gathering of the Veterans of Foreign Wars. “And the federal bureaucracy will not slow that action down.”

In addition to Weightman’s resignation, Defense Secretary Robert Gates forced Army Secretary Francis Harvey to step down last Friday. In addition, Gates replaced Lt. Gen. Kevin C. Kiley, who was named interim commander of Walter Reed, which he had led from 2000 until 2004, when he became Army surgeon general.