NEW YORK — With more and more U.S. troops dying in Iraq, emotions on the American home front are increasingly conflicted.
In Crawford, Texas, a tent city of antiwar families sprung up around a mother who lost her son in the war and wants to speak to President Bush. In Washington, several prominent Republicans are demanding troop withdrawals next year.
Just as forcefully, the sister of an Ohio soldier killed recently says the U.S. must continue to fight so his death will not have been in vain. Back in Crawford, pro-Bush demonstrators are trying to outshout the antiwar contingent.
Is this a breakthrough moment, when public sentiment shifts dramatically against a conflict, as it did during the latter part of the Vietnam War? Or is it just a low point in a war that ultimately the country will be proud to have waged?
Watershed events usually are identified by scholars years after a war ends. Still, elements of the present conflict have echoes of previous wars -- and many historians believe a comparison with those moments can shed light on the American home front today.
"When Americans see the war that is being fought as somehow connected to larger purposes, that makes the war and its sacrifices more palatable," said Andrew J. Bacevich, a Vietnam veteran and professor of international relations at Boston University.
"If Americans begin to see that a war does not connect to larger purposes, then their willingness to sacrifice and continue supporting an administration declines. In short, we want our wars to mean something."
There were few misgivings about the need to fight World War II because America had been attacked at Pearl Harbor. Most Americans also were eager to stop Hitler's Germany from taking over all of Europe.
The same cannot be said of the Iraq war because of the debate over whether Saddam Hussein's regime had any link to the Sept. 11 attacks. The futile search for weapons of mass destruction also made skeptics of many on the home front.
"World War II had lots of discouraging moments, but almost everyone saw that it had to be carried out to its conclusion," said historian Geoffrey C. Ward, whose 14 books include one on the Civil War.
"The difference here is that increasing numbers of people aren't sure it is worth it."
Vietnam may offer a better analogy, because the underlying argument for that conflict -- the need for the United States to fight communist expansion -- gradually gave way to a belief that the war was bogged down in a quagmire that was killing thousands of Americans a year. The public can rapidly lose faith in leaders if it does not think a conflict is winnable.
When public opinion tilted against the Vietnam War after the Tet offensive in 1968, President Johnson chose not to seek reelection.
Yet the comparison has limits.
There was a national draft during Vietnam that caused millions of parents to fear that their sons could be sent to war. That war also spawned a protest movement that seemed to aim much of its anger at U.S. forces. The Iraq war is being fought by an all-volunteer army, and most critics make a point of condemning the war, not the warriors.
Still, the same fears of a morass are slowing surfacing about Iraq, some historians say.
"I think we're looking at a watershed moment now, because this Iraq war stands in the shadow of the Vietnam War and all the failures we associate with it," said Robert Dallek, a biographer of Presidents Johnson and Kennedy.
"More and more people have the feeling that we're trapped in quicksand in Iraq, just as they did in Vietnam, and I don't see how Bush can regain enough credibility to say things aren't that bad," Dallek said. "He sounds like Johnson did, always saying there is light at the end of the tunnel, and the fact is people don't believe him."
Public opinion might swing in favor of the war if victory is in sight. Iraqis are expected to vote in October on a constitution, and Hussein's trial may begin within several months. Both events could play a key role in building support for the war.
But, as in Vietnam, the initial American effort to fight a conventional war in Iraq has given way to the deadly unpredictability of a guerrilla war.
The Bush administration has repeatedly said that the invasions of Afghanistan and Iraq were necessary after the Sept. 11 attacks. Bush also has consistently maintained that sacrifices are needed to win the global war on terrorism.
Those arguments continue to persuade some Americans, said David Gergen, a public policy professor at Harvard University's John F. Kennedy School of Government and a former advisor to four presidents.
"I think people are really worried that if we get out of Iraq the end result will be worse, because of the fear of terrorism," Gergen said. "That has sustained the president."