How anti-war protest movements have made the U.S. stronger.

Since the bombs began falling last week, critics of the invasion, from Sen. Tom Daschle to Michael Moore, have drawn brickbats for not stifling their sentiments. War has begun, it was said, so dissent must end. It's not simply hawks who are telling war opponents to shut up. On the NewsHour With Jim Lehrer, the normally estimable Walter Russell Mead said, "Unless you are a pacifist and opposed to all war, I think once the shooting starts, you need to … give it a rest." His interlocutor, Zbigniew Brzezinski, agreed.

If dissenters were to follow this advice, it would be not only a mistake, but a historic first. Protesting war isn't some Vietnam-era relic, like love beads or Country Joe McDonald, but an American democratic tradition.

Last month, hundreds of peace groups the world over staged Aristophanes' Lysistrata­—a play that reminds us that anti-war movements are as old as war itself. In American history in particular, wartime dissent has a venerable lineage. Even during that most mythic of causes, the Revolution, fully one third of Americans opposed independence, in John Adams' famous estimate, while an equal third favored it. Only in retrospect did the Revolution become an unambiguously glorious endeavor.

Dissenters spoke out against virtually every subsequent conflict. The humiliating defeats of the War of 1812 made that fight so unpopular that the states of New England considered seceding from the Union. A generation later, many Americans viewed the Mexican-American War (not unreasonably) as an act of naked U.S. aggression. In 1848, shortly after the war's conclusion, Congress censured President James Polk for "unnecessarily and unconstitutionally" commencing hostilities. Supporting the rebuke was Illinois Rep. Abraham Lincoln, who attacked Polk as "a bewildered, confounded and miserably perplexed man."

Popular support for the Spanish-American War waned as the relatively easy fight for a free (i.e., pro-American) Cuba gave way to a more controversial program of wresting away Spain's other colonies, particularly the Philippines. When President William McKinley opted to annex the Philippines—he wanted, he said, "to educate the Filipinos and uplift and Christianize them"—a motley array of critics from Andrew Carnegie to Mark Twain objected. William Jennings Bryan used his dissenting stance as the centerpiece of his (losing) 1900 presidential campaign.

During World War I, critics excoriated Woodrow Wilson—who had run for re-election in 1916 on the slogan "He kept us out of war"—for entangling America in a bloody European conflict. Political leaders from Wisconsin Sen. Robert LaFollette to Socialist Party presidential candidate Eugene V. Debs spoke out. ("I had supposed until recently that it was the duty of senators … to vote and act according to their convictions," LaFollette sardonically told the Senate. "Quite another doctrine has recently been promulgated by certain newspapers … and that is the doctrine of 'standing back of the president' without inquiring whether the president is right or wrong.") The majority of Congress, however, passed a series of repressive laws that let the government imprison or deport thousands of critics of the president, including Debs. Vigilante groups ostracized, assaulted, and even lynched countless more.

In fact, the only major war that lacked an organized bloc of dissenters was World War II: Pearl Harbor had made an isolationist stance untenable, and as Americans learned more and more about Nazi Germany, most anti-war activists decided the defeat of fascism was worth fighting for. (Some rejoined peace movements, such as the nascent anti-nuclear effort, at the war's end.) Still, even during the "Good War," critics persisted. On the left, pacifists served prison time for refusing to fight or perform compulsory alternative service. On the right, congressional Republicans launched an investigation of Pearl Harbor, with some implying that Franklin Roosevelt had foreknowledge of the attack.

The case for dissent rests on more than its lineage. Critics of war—even when they've been wrong, or their comments distasteful—have done far more good than harm. Although enemy leaders may take heart from knowing that Americans are divided, the mere expression of opposition has never materially hurt any U.S. military campaign. Except perhaps for the Revolution's Loyalists, no dissenters have aided America's adversaries in large numbers. When, as in Vietnam, conditions like flagging troop morale have undermined battlefield success, it was the soldiers' awareness of the war's futility—not the protests back home—that created those conditions. The sense that the war was unwinnable fueled the peace movement, not the other way around.

In short, the claim that by protesting dissenters are showing insufficient "support" for the troops is specious. Does anyone really believe that doves wish ill upon American fighting men and women? Sometimes hawks cite stories that Vietnam anti-war activists vilified or even spit on returning veterans—stories, as Jack Shafer wrote in May 2000, that range from the overstated to the bogus. In fact, like almost all anti-war movements, anti-Vietnam demonstrators argued for peace in the name of the grunts being sent to die. Remember Vietnam Veterans Against the War?

Not only have anti-war movements caused the nation little direct injury; they've made positive contributions. Dissent has produced important works of American political and social thought. Henry David Thoreau wrote his classic Civil Disobedience as a cri de coeur against the Mexican-American War ("the work of comparatively a few individuals using the standing government as their tool"). Randolph Bourne wrote his greatest essays protesting World War I.