of America’s civic health that political leaders and public intellectuals are today more circumspect about limiting civil liberties in times of national crisis. But even raising the question pits freedom and national survival against each other and assumes that the exigencies of war invite nothing but perils to American democracy.

History tells us something different. Several of America’s past wars have forced citizens to struggle over their rationale for fighting. And out of these internal debates have come vigorous new ideas about the meaning of liberty and freedom.

Take the War for Independence. Most American revolutionaries began the 1770s determined to separate from Britain and establish a pure republic. The historian Gordon Wood writes that the ideal society they envisioned required “a particular sort of egalitarian and virtuous people: independent, property-holding citizens who were willing to sacrifice many of their private, selfish interests for the res publica, the good of the whole community.”

At the start of the rebellion, American revolutionaries viewed the national community as organic and feared that the existence of private or group interests might undermine the nascent republic. To be sure, their ideology was radical for its time. “Equality lay at its heart,” says Wood. “It meant a society whose distinctions were based only on merit.” It meant an end to monarchy and aristocracy. Yet republicanism was also anti-democratic: It rejected the idea that a single nation could entertain diverse economic, religious, and political interests.

Revolutionary ideology wasn’t a constant. The very act of rebellion forced colonial leaders to argue over and hash out the meaning of freedom. The historian Bernard Bailyn believes that on ” fundamental issues—representation and consent, the nature of constitutions and of rights, the meaning of sovereignty—… the colonists probe[d] and alter[ed] the inheritance of thought concerning liberty and its preservation.” This is surely what Benjamin Rush had in mind in 1787 when he declared, “The American war is over; but this is far from being the case with the American revolution.”

Colonial leaders who had chafed under British control had described their afflictions as “enslavement.” Gradually, as the logical implications of their opposition to metaphorical slavery became clearer to them, many revolutionaries came to believe that actual chattel slavery was inimical to their cause. This ideological development led to the gradual abolition of slavery in the newly formed Northern states and to serious debates about it in states like Virginia and, later, Kentucky.

The Revolution unleashed other new ideological forces. Even as its leaders struggled to articulate their vision for a new nation and government, the sheer economic, ethnic, and religious diversity of America’s population forced a reconsideration of the old republican rejection of factions. Ultimately, Wood says, the Founding Fathers “recognized the reality of an American society composed of many conflicting private interests,” and this realization gave the new nation democratic ways of thinking

and of governing, among them, political parties. None of this would have been possible before the war.

The Civil War also made Americans expand their definitions of freedom and liberty. In 1860, Abraham Lincoln and the Republican party ran on a platform that pledged only to stop slavery’s expansion into the Western territories—not to abolish it outright or even gradually. Still, this was too radical for most voters in the Solid South and the border states and even for a considerable portion—perhaps 46 percent—of the Northern electorate.

For almost two years into his presidency, Lincoln took pains to accommodate the nation’s fundamental conservatism and effectively embraced the Democratic party’s rallying cry: “The Union as it was, the constitution as it is.” In a nod to borderstate slave owners and Northern Democrats, he twice overruled radical Union generals who attempted on their own authority to liberate slaves within captured Confederate territories. In a famous letter to Horace Greeley, dated August 1862, he identified as his “paramount” objective the restoration of the Union. If he could accomplish this task without freeing a single slave, he would.

But the war was proceeding on a trajectory of its own. Lincoln later admitted in his second inaugural address that most Americans had understood from the start that slavery was “somehow” the cause of the conflict. And, as 1862 wore on, without an end in sight, many Northerners began to see the logic in attacking secession at its apparent roots. That spring, Congress banned slavery in Washington, D.C., and the Western territories and passed a confiscation act that allowed for the expropriation of slave property. Finally, on September 22, Lincoln issued the preliminary emancipation proclamation, though he didn’t predicate it on the morality of abolition but rather on the strategic necessity of undermining the South’s economic and military efforts.

Lincoln’s issuance of the final Emancipation Proclamation in January 1863 sparked heated argument among hundreds of thousands of Union soldiers, who contested the merits of black freedom by campfires, in tents, and even in formal, regimental debate societies. A handful of companies from the Midwest laid down their arms and returned home. Many other soldiers bridled at the thought of fighting to liberate slaves. But the vast majority continued to serve.

Complicating this debate were three phenomena that led to a gradual but critical shift in Northern and, more particularly, military opinion. To begin with, many Union troops gained firsthand exposure to slavery, which brought them to believe that there was, in fact, something fundamentally immoral about it. Second, the bravery of all-black regiments like the 54th Massachusetts made many white soldiers and civilians reconsider their old prejudices. And toward war’s end, many of the Union’s nearly two million soldiers found ennobling their role as an army of liberation.

By late 1863, Lincoln was speaking of a “new birth of freedom” for America. A year later, he won 78 percent of the soldier vote, on a platform calling explicitly for the abolition of slavery. And just

before his assassination he promised that should the war continue, “all the wealth piled by the bondman’s two hundred and fifty years of unrequited toil shall be sunk, and… every drop of blood drawn with the lash, shall be paid by another drawn with the sword.”

That same year, Congress and the states ratified the Thirteenth Amendment, and the federal government subsequently enacted two additional amendments guaranteeing full citizenship and due process of law to African-Americans and banning electoral disenfranchisement on grounds of race. None of this had been remotely imaginable, let alone possible, in 1860.

The Civil War was in many respects an unfinished revolution. Most of the constitutional gains of the 1860s went unenforced for another century. Nevertheless, what began as a very limited war ended with a deeply radical outcome.

World War II offers a final example of how wartime mobilization can lead to a greater domestic liberty. In the two decades before Pearl Harbor, Americans continued to allow overt forms of bigotry. Throughout the 1910s, the Ku Klux Klan found receptive audiences for its antiblack, anti-Jewish, and anti-Catholic agitation in many Northern and Western cities, while the nation’s most prominent industrialist, Henry Ford, financed the publication and dissemination of the Protocols of the Elders of Zion, an already hoary Russian hoax that purported to be a Jewish plot to take over the world. Mobilization for World War II forced Americans to confront racism, bigotry, and the rougher edges of their culture.

The 1930s were little better—they saw the rise of the likes of the immensely popular anti-Semitic radio-show host Father Coughlin—but World War II helped make bigotry unfashionable. As early as 1938, the mounting struggle against European fascism inspired leading social scientists and biologists to openly renounce their professions’ recent faith in anthropological racism and eugenics, and popular culture followed once the war was on. By 1942, the Office of War Information was working closely with Hollywood to produce motivational “platoon films,” featuring multiethnic casts of brave young soldiers—the Irishman from Boston, the Italian from New York, the Jew from Brooklyn, the Pole from Chicago. Occasionally, as in Bataan and Guadalcanal Diary (both from 1943), an African-American would appear, although the Army remained segregated throughout the war.

In Pride of the Marines, a wounded Jewish Marine named Lee Diamond articulates what had by now become the central American message: “One happy afternoon when God was feeling good, he sat down and thought up a beautiful country and named it the U.S.A…. Don’t tell me we can’t make it work…. Maybe some guys won’t hire me because my name is Diamond and not Jones. ‘Cause I celebrate Passover instead of Easter….We need a country to live in where no one gets booted around for any reason.”

By 1945, public displays of racism and bigotry were falling increasingly out of favor,

in no small part because wartime mobilization forced Americans to confront the rougher edges of their culture. The Saturday Evening Post, which in 1933 had saluted Hitler’s staunch anticommunism, now labeled Theodore Bilbo, the Mississippi senator known for his racist views, America’s most dangerous bigot. Many municipal and state governments enacted anti-discrimination housing and employment codes in the 1940s and 50s, and Southern segregationists recast their beliefs as emanating from States’ Rights, rather than white supremacy.

Faced with the need to forge national unity in a time of crisis, Franklin Roosevelt had repeatedly defined the war effort as a death struggle “between human freedom and human slavery.” His “Four Freedoms” campaign was the centerpiece of this effort. In 1943, The Saturday Evening Post published Norman Rockwell's renderings of the freedoms with accompanying essays by Stephen Vincent Benét, Booth Tarkington, Will Durant, and Carlos Bulosan. “Freedom of Speech” and “Freedom of Worship” may have inspired some Americans to think more seriously about the virtues of democracy. The historian Eric Foner has written that “their prominent place among the Four Freedoms accelerated the process by which the Bill of Rights, and especially the First Amendment, moved to the center of Americans’ definition of liberty.” “Freedom From Fear” and “Freedom From Want” worked in more subtle ways, giving voice to Roosevelt’s deep conviction that “there can be no real freedom for the common man without enlightened social policies.” In this way, they, too, helped advance expansive notions about liberty.

The point here is not that wars necessarily change society for the better. The best of them are violent, bloody, and destructive, and each of these examples ended with its expansion of liberty and freedom stopping short of complete equality.

But, as in the 1770s, the 1860s, and the 1940s, today the exigencies of war—in whatever shape it ultimately assumes- afford Americans an opportunity in the form of a challenge. To keep the nation unified and to convince the world that its cause carries merit, the United States will have to articulate its purpose. As indeed the President began to do very soon after the attack, when, before a group of American Muslim leaders, he said, “America counts millions of Muslims amongst our citizens…. And they need to be treated with respect…. Those who feel… they can intimidate our fellow citizens to take out their anger don’t represent the best of America….” We will have to make very clear exactly why American democracy is superior to dictatorship and theocracy, and this in turn will force us to examine our most deeply cherished institutions and beliefs. In the past, this exercise, although brought on by painful and urgent circumstances, has ended by giving us a more honest application of our founding ideals.