Few traditions are more American than freedom of speech and the right to dissent. But an equally powerful American tradition has been the effort by government and private “patriots” to suppress free expression in times of crisis. During the fighting in Iraq, former military leaders who criticized planning for the war were denounced for endangering troops in the field and warned to remain silent. A number of scholars, including myself, were branded “Traitor Professors” on a television talk show. If criticism of a war while it is in progress makes one a traitor, that category will have to include Abraham Lincoln, who denounced the Mexican War while serving in Congress in 1847; Mark Twain, who vehemently attacked government policy in the Spanish-American and Philippine wars at the turn of the last century; and Martin Luther King Jr., who eloquently called for an end to the war in Vietnam.

With the exception of World War II, every significant war in American history has inspired vigorous dissent. Many colonists remained loyal to Britain during the American Revolution. Most New Englanders opposed the War of 1812. Numerous Americans considered the Mexican War an effort to extend the territory of slavery. Both North and South were internally divided during the Civil War. World War I and Vietnam produced massive antiwar movements. This is part of our democratic tradition.

Equally persistent, however, have been efforts to suppress wartime dissent. The Alien and Sedition Acts during the “quasi-war” with France in 1798 allowed the President to deport aliens and made it illegal to criticize the government. Both Union and Confederate governments suppressed opposition newspapers and jailed critics. World War I witnessed a massive repression of freedom of speech, with critics of the war, socialists and labor leaders jailed or deported, those suspected of disloyalty rounded up by private vigilantes and the speaking of German banned in some places. Universities, including my own, fired professors who opposed American involvement.

Self-proclaimed patriots not only seek to determine the boundaries of acceptable speech about the present but rewrite history to create a more politically useful past. During World War I, the Committee on Public Information, a government propaganda agency, published pamphlets demonstrating the “common principles” of Oliver Cromwell, Jean-Jacques Rousseau and Thomas Jefferson in order to create a historical lineage for the Anglo-French-American military alliance. Today, statements about history that in normal times would seem uncontroversial have been labeled treasonous. Daniel Pipes said in his syndicated newspaper column that I “hate America” because I noted that Japan invoked the idea of pre-emptive war to justify its attack on Pearl Harbor (a point also made by that well-known anti-American, Arthur Schlesinger Jr.). My comment to a reporter that the United States has frequently embarked on military ventures without being attacked, as in Haiti, the Dominican Republic and Vietnam, prompted accusations of treason in the media.

In the aftermath of the Civil War, a far greater crisis than the war on Iraq, the Supreme Court in the Milligan case invalidated the use of military tribunals to try civilians. The Court proclaimed that the Constitution is not suspended in wartime: “It is a law for rulers and people, equally in war and in peace.” Alas, we have not always lived up to this ideal. The history of civil liberties in the United States is not a straight-line trajectory toward ever-greater freedom. It is a complex story in which victories can prove temporary and regression can follow progress.

Our civil liberties are neither self-enforcing nor self-correcting. Historians today view past suppressions of free speech as shameful episodes. But we are now living through another moment when many commentators, both in and out of government, seem to view freedom of expression as at best an inconvenience and at worst unpatriotic. The incessant attacks on dissenters as traitors are intended to create an atmosphere of shock and awe within the United States, so that those tempted to speak their mind become too intimidated to do so.

George W. Bush has claimed that America’s enemies wish to destroy our freedoms. If we surrender freedom of speech in the hope that this will bring swifter victory on current and future battlefields, who then will have won the war?