Washington ? Once, nearly four decades ago, Congress rushed into war without asking questions. Now the questions that Congress didn’t ask in 1964 and questions that grew out of the deepening Vietnam conflict that year are being asked on Capitol Hill.

History never repeats itself, but embedded in the increasingly serious debate about Iraq policy are issues that grow directly out of the divisions over the Vietnam War and the Washington policy failures of the 1960s and 1970s. And now that members of the Vietnam generation are in important political positions, these questions have taken center stage in the capital.

“There’s never been a conflict since Vietnam where the echoes of Vietnam haven’t been heard,” Sen. John McCain Jr., the Arizona Republican who was a prisoner of war in Hanoi during the Vietnam War, said in an interview.

In truth, the language surrounding the war in Afghanistan how an open and democratic people faces the forces of evil contained many echoes of the rhetoric of World War II. But the language surrounding the potential war against Iraq the concerns about secrecy, the worries about public support for conflict is replete with the echoes of Vietnam.

In the Vietnam era, the questions came after the war intensified, not as the conflict was unfolding. Historians have raised grave questions about the naval incidents in the Gulf of Tonkin in August 1964, but at the time, President Lyndon B. Johnson vowed “to take all necessary measures in support of freedom, and in defense of peace, in Southeast Asia.” Congress responded promptly, and resolutions in support of the use of U.S. military force were passed unanimously in the House and with only two dissenting votes, both from Johnson’s own party, in the Senate. One of the two principal Democratic sponsors of the Senate bill was J. William Fulbright of Arkansas, who later broke with the president on the war and asked many of the questions Iraq skeptics are posing today.

Now, President Bush has agreed that any military action he undertakes in Iraq should be preceded by congressional approval, presumably in the form of a resolution that, while having no force of law, nonetheless possesses immense moral and symbolic force. But before that resolution passes, the president and administration officials once again will have to confront these questions with roots in the Vietnam years:

What are the things that the American people aren’t being told about the Iraq situation? Senate Majority Leader Tom Daschle, the South Dakota Democrat, raised that question, saying, “We learned the lessons of secrecy during Vietnam.” At the heart of the “secrecy” issue is the notion that administration officials are justifying an invasion of Iraq by arguing that if their critics knew what they knew, then the critics would believe as they do. That issue is what led to the “credibility gap” during Vietnam, which in turn helped assure that Johnson didn’t run for re-election in 1968.

“I worry about the secrecy issue,” said McCain. “The more information the administration has, the more it should share.

“My support for regime change in Iraq has a lot to do with the fact that Saddam Hussein is a guy who doesn’t keep his word and broke arms-inspection agreements. Others want to see more evidence, and they have a clear right to that. I don’t think anything should be withheld.”

What is the nature, and length, of the American commitment likely to be? Daschle is troubled about the prospect of substantial American casualties followed by a lengthy American presence in a new Iraq; the public’s appetite for either of those is likely to be small. Some experts believe the United States could be in the position of occupying Iraq for as long as a decade, which would try Americans’ patience and exacerbate tensions with Arab nations. In any case, this issue has not been aired fully yet.

Does this military effort abroad have substantial and enduring political support at home? No one doubts that the moment American soldiers, sailors and aviators are engaged in combat, the nation will be behind their efforts. That was in the case in Vietnam at the beginning: Among the senators supporting the hastily drafted Gulf of Tonkin resolution in 1964 were many of the Democrats who would lead the battle against the war by the end of the decade, including Eugene McCarthy of Minnesota, George S. McGovern of South Dakota, Frank Church of Idaho, Edmund S. Muskie of Maine and Albert Gore Sr. of Tennessee.

This time lawmakers say they want to be sure to ask questions first, and they want to be sure the case for military involvement is made more persuasively than it was in 1964 or in the years to come. “We learned the lessons of what it is to move without public support in Vietnam,” said Daschle. Recently released tapes of President Johnson’s Oval Office conversations make it clear that one of the reasons the case wasn’t made in 1964 was that the president himself was uneasy about the course he was taking.

That is not the case this time. Last week President Bush made his opening argument. Even his allies agree that the three Vietnam questions will have to be answered before he completes his closing argument.