The three most significant US wars since 1945 - Korea, Vietnam, and now Iraq - share an important trait: As casualties mounted, American public support declined.
In the two Asian wars, that decline proved irreversible. With Iraq, the additional bad news for President Bush is that support for the war in Iraq has eroded more quickly than it did in those two conflicts.
For Mr. Bush, low support for his handling of the war - now at 35 percent, according to the latest Gallup poll - has depleted any reserves of "political capital" he had from his reelection and threatens his entire agenda. Last week's bombshell political developments, both the bipartisan Senate resolution calling for more progress reports on Iraq and the stunning call for withdrawal by a Democratic hawk, Rep. John Murtha of Pennsylvania, have not helped.
But the seeds of Bush's woes were planted early on. Just seven months into the Iraq war, Gallup found that the percentage of Americans who viewed the sending of troops as a mistake had jumped substantially - from 25 percent in March 2003 to 40 percent in October 2003.
In June 2004, for the first time, more than half the public (54 percent) thought the US had made a mistake, a figure that holds today.
With Vietnam, that 50-percent threshold was not crossed until August 1968, several years in; with Korea, it was March 1952, about a year and a half into US involvement.
Why did Americans go sour on the Iraq war so quickly, and what can Bush do about it?
John Mueller, an expert on war and public opinion at Ohio State University, links today's lower tolerance of casualties to a weaker public commitment to the cause than was felt during the two previous, cold war-era conflicts. The discounting of the main justifications for the Iraq war - alleged weapons of mass destruction and support for international terrorism - has left many Americans skeptical of the entire enterprise.
In fact, "I'm impressed by how high support still is," Professor Mueller says. He notes that some Americans' continuing connection of the Iraq war to the war on terror is fueling that support.
In addition, intense political polarization gives Bush resilient support among Republicans.
But among Democratic voters who supported the US-led invasion initially, most have long abandoned the president. In polls, independent voters now track mostly with Democrats. And, analysts say, once someone loses confidence in the conduct of a war, it is exceedingly difficult to woo them back.
"[Bush's] best option is bringing peace and security to Iraq," says Darrell West, a political scientist at Brown University. "If he can accomplish that, people will think the war's going well and that he made the right decision. But that's proving almost impossible to achieve."
Pollster Daniel Yankelovich, writing in the September/October 2005 issue of Foreign Affairs magazine, states that "in my judgment the Bush administration has about a year before the public's impatience will force it to change course."
Not helping the president has been the modern phenomenon of 24/7 cable news coverage, which brings instant magnification to the daily death toll and the longstanding media practice of focusing on negative developments.
And there is the lingering public memory of Vietnam itself, which, in the Iraq war, may have made the public warier sooner of getting stuck in a quagmire.
Scholars like Mueller at Ohio State speak of an emerging "Iraq syndrome" that will have consequences for US foreign policy long after American forces pull out - particularly in Washington's ability to deal forcefully with other countries it views as threatening, such as North Korea and Iran.
"Iraq syndrome" seems to be playing out, too, with the American public. The just-released quadrennial survey of American attitudes toward foreign policy - produced jointly by the Pew Research Center and the Council on Foreign Relations - shows a revival of isolationism. Now, 42 percent of Americans say the US should "mind its own business internationally and let other countries get along the best they can on their own" - up from 30 percent in 2002.
According to Pew Research Center director Andrew Kohut, that 42 percent figure is also similar to how the US public felt in the mid-1970s, at the end of the Vietnam War, and in the 1990s, at the end of the cold war.