A review of Sword of the Spirit, Shield of Faith: Religion in American War and Diplomacy, by Andrew Preston

n September 14, 2001, just three days after the attack on the World Trade Center and the Pentagon, President George W. Bush gave a speech at the National Cathedral in Washington, in which, among other things, he called for a national day of prayer and remembrance. During the speech he stressed the link between religion and democracy; the importance of religious liberty; the blessing of America's mission in the world; the tragic necessity of using force to vindicate justice in an unjust world; the presence of evil as a test for the faithful; and the responsibilities that come with power and wealth.

The president made clear what would come next:

war has been waged against us by stealth and deceit and murder. This nation is peaceful, but fierce when stirred to anger. The conflict was begun on the timing and terms of others. It will end in a way and at an hour of our choosing.

All this was not in the hands of a mere president or even of the American people; it was in the hands of God. "As we have been assured, neither death nor life, nor angels nor principalities nor powers, nor things present nor things to come, nor height nor depth, can separate us from God's love…may he always guide our country. God bless America."

Bush also used such language in the run-up to the war in Iraq. In his 2003 State of the Union Address, the president proclaimed that "the liberty we prize is not America's gift to the world" but "God's gift to humanity."

Many Americans were uncomfortable with Bush's rhetoric, contending that his use of religion to frame and justify war was somehow at odds with the American tradition. Their unease suggested that American foreign and national security policy belongs exclusively to the hardheaded world of balances of power and the rational calculation of interests, cost, and risk. But as Andrew Preston shows in his fine book, Sword of the Sprit, Shield of Faith, religion continually has played a major role in American war and diplomacy, since even before the founding of the Republic.

There have been other books on aspects of the intersection between religion and American foreign policy, but Preston's is the first comprehensive survey of the topic. As he notes, historians of religion have rarely examined diplomacy and war, and military and diplomatic historians have just as infrequently taken a serious look at religion. Although some diplomatic historians note the personal religious beliefs of the "usual suspects"—Woodrow Wilson, John Foster Dulles, and Jimmy Carter—most treat religion as "background noise" in the study of American diplomatic history.

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Preston, a fellow of Cambridge University's Clare College, begins his account with the colonization of North America. Like the Spanish before them, the British who settled in the New World did so in the name of God, in this case, the God of the Protestant confession. The early English colonists saw their effort as sacred: establishing a "New Jerusalem" that would doom the great French and Spanish Catholic conspiracy to destroy Protestantism, and defeating the "heathen onslaught" by the Indians in the New World. After its establishment, this Protestant New Jerusalem "would spend the next century pushing back Catholics and Indians, and all others who would deny them their sacred errand."

Preston calls the British imperial wars and their manifestation in North America "wars of permanent reformation." Although the Peace of Westphalia in 1648 removed the basis for wars of religion within Christendom by establishing the principle ofcuius regio, eius religio (whoever's realm, his religion), which, when secularized becomes the basis of state sovereignty, Protestant fear of Catholic hegemony remained a powerful motivation for British foreign policy toward France, both in Europe and North America.

As Preston writes, "the most important, mutually reinforcing components to colonial identity were robust notions of political freedom and the Protestant religion, forced together through a series of imperial wars that had starkly different meanings for the American colonists than they did for Britons." This meant that the emerging American worldview possessed a "distinctively pious tenor" giving rise to an "American revelation" and a fusion between politics and religion that Preston calls "liberation theology."

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Though the most prominent founders were not particularly religious, he argues, unlike the leaders of the French Revolution they harnessed religion to the cause of republican government. They appealed to a Christian republicanism that blended Protestant theology and democratic politics. Many political philosophers of early modernity did not believe such a fusion possible, but it was helped along by the Great Awakening of the 1740s, which rendered religion in America less hierarchical than in England.

Preston contends that Christian republicanism was integral not only to internal American politics but to American foreign policy: "in a very modern sense, Americans believed that a state's internal character influenced its external behavior." This is the basis of the idea of what has come to be called "the democratic peace." But it also gave rise to the notion that a cure for the corruption within states that leads to aggressive war is the spread of democracy itself. "If Americans could not feel safe in a world without republican virtue, the solution was obvious: spread the virtue and its attendant blessings of liberty—which to many Americans also meant the spread of Christianity." This revolutionary idea has contributed to adventures (or misadventures) abroad from Manifest Destiny to the Iraq War.

Also important was the founders' separation of church and state. They understood that a republic could not function properly if it did not safeguard religious liberty. And this applied in foreign enterprises as well. As Americans prepared to invade Canada in 1775, George Washington ordered the commanders of the expedition to "avoid all Disrespect to or Contempt of the Religion" of the French. "While we are Contending for our own Liberty, we should be very cautious of violating the Rights of Conscience in others; ever considering that God alone is the Judge of the Hearts of Men and to him only in this Case they are answerable." We hear an echo of this admonition in the instructions to the troops during operations in Iraq and Afghanistan.

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Between the War of 1812 and the Civil War, the issues that divided America divided her churches—how to reconcile slavery and democracy? expansion with republican government? empire with liberty?—and those divisions affected U.S. foreign policy, too, as Preston shows. At the same time, immigration was changing the religious character of the United States. The influx of large numbers of Roman Catholics, most from Ireland, meant that Protestantism ceased to be as dominant as it had been in the 18th century. The issue came to a head with the Mexican War, during which anti-Catholic bias in the Army contributed to high desertion rates among immigrant Irish soldiers. Many joined the Mexicans, who formed the San Patricio battalion for their Irish co-religionists. The Mormons created their own regiment within the Army, "the only faith-based regiment in American military history."

Preston argues that the Civil War "deeply affected the nation's ideology, especially Americans' general worldview and sense of world mission, in ways that would shape both U.S. foreign policy and international politics for decades to come." The Republican Party's 1900 campaign platform used Lincolnian language to justify the recently concluded war with Spain: the Spanish-American War had been fought for "high purpose"; it was a "war for liberty and human rights" that had given "ten millions of the human race" a "new birth of freedom" and the American people "a new and noble responsibility…to confer the blessings of liberty and civilization upon all the rescued peoples."

Soon statesmen of both parties would speak of the Civil War as America's first great moral crusade and World War I as its second. It was not Woodrow Wilson but Teddy Roosevelt who declared: "[A]s our fathers fought with slavery and crushed it, in order that it would not seize and crush them, so we are called on to fight new forces." It was not Wilson but Henry Cabot Lodge who called World War I "the last great struggle of democracy and freedom against autocracy and militarism." These same statesmen justified U.S. military interventions in Latin America and the Caribbean as a means of spreading liberal principles abroad.

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It is often argued that until the end of the 19th century, American foreign policy was based on "virtuous isolationism"—the idea that the United States was an exemplar of liberty and nothing more. But as Preston shows, American statesmen, motivated by piety and morality, had often embraced the mission of spreading liberal principles abroad for the betterment not only of America but of the world.

If World War II represented the apex of America's moral mission in the world, the Cold War called that very mission into question. The lack of consensus was partly the result of increasing religious diversity. Jewish voices joined Protestant and Catholic in the debate. Churches were often split over the question of nuclear weapons, and Vietnam shattered any religious consensus regarding foreign policy. Preston's treatment of this period is especially riveting.

As the examples of Jimmy Carter, Ronald Reagan, Bill Clinton, and George W. Bush show, religion can still shape at least the rhetoric of U.S. foreign policy. But in most cases, the link between religion and foreign policy has seemed tenuous in recent years. To say the least, Barack Obama appears to lack the religious and moral fervor of his predecessor—he comes, after all, from the church of "God damn America!" and seems to pray for American decline. Such prayers rise from many pews these days, not least in the mainstream Protestant denominations that are experiencing their own decline.

Nonetheless, evangelical churches are growing and Americans are still far more religious than Europeans, whose own spiritual indifference seems to leave them tired and uncertain in the face of resurgent Islam. As militant Islam probes for weakness in the world once called Christendom, anyone who wishes to understand religion's influence on America's past wars, and its continuing influence on American foreign policy generally, would do well to consult Andrew Preston's erudite and balanced treatment.