In 1943, Walter Lippmann published U.S. Foreign Policy: Shield of the Republic, perhaps the most influential popular case for strategic realism in American history. Lippmann warned that the nation’s experience of insularity and free security during the 19th century had blinded his countrymen to the realities of power. “Americans have forgotten the compelling and, once seen, the self-evident common principle of all genuine foreign policy,” Lippmann wrote. “This is the principle that in foreign relations, as in all other relations, a policy has been formed only when commitments of power have been brought into balance.” The United States, Lippmann insisted, must seek security in the solvency of power.

Robert Kagan puts forward a rather different self-evident principle in the first of a two-volume history of American foreign policy, provocatively titled Dangerous Nation. For Kagan, senior associate of the Carnegie Endowment for International Peace and contributing editor to the Weekly Standard, U.S. foreign policy is the sword of the republic. Even during its formative years America was never a modest, insular nation. That was a comforting myth that began with Benjamin Franklin and Thomas Paine and is promoted today by conservative, realist, and leftist opponents of an assertive American foreign policy. The dominant strain in the national character has always been “messianic” and activist. Kagan’s account ends with the Spanish-American War, but it is not hard to see where his second volume will take him. America’s desire to make the world safe for democracy was hardly an innovation of Woodrow Wilson, an aberration of the Cold War, or a bizarre pathology of George W. Bush.

By the same token, Kagan notes, suspicion and hatred of America are not copyrighted by aggrieved Muslims or a poetry-writing French foreign minister. Metternich complained about us two centuries ago. America has always been considered dangerous—a threat not only to old Europe and modern tyranny but to all who reject our intrusive form of liberalism, from Native Americans to modern opponents of globalization.

Kagan suggests that the most dangerous foreign policy gap is not between our resources and commitments, but between a falsely modest self-image and historical reality. He denies that the nation has lately become too militaristic, idealistic, arrogant, or imperial—and that only a more modest, considerate America can reclaim hearts and minds abroad. Kagan writes not merely as a historian but as the implicit advocate of an approach to the world—call it what you will: neoconservative, Reaganite, Bush Doctrinaire—that since the Iraqi invasion has come under withering political attack. In his own work and in association with William Kristol and the Weekly Standard, Kagan has been an articulate defender of this point of view. But he has never been its uncritical cheerleader. This book is no exception. He writes with great insight, and not a little diffidence, about the American character.

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Americans, he reminds us, expanded relentlessly throughout the 18th and 19th centuries. They drove the Indians off millions of acres of land and almost out of existence. The New World empires of France, Spain, and Russia succumbed to this push as well. Expansion was supported not just by ill-tempered nationalists like Andrew Jackson but by such enlightened men as George Washington, Thomas Jefferson, and John Quincy Adams. American merchants sailed everywhere in search of commerce. A martial people, our forebears did not shy from using force to support their push for land, markets, and honor.

Kagan argues that American expansionism differed in one critical respect from that of other empires, such as Russia. Our liberal republicanism elevated the rights of the individual over the state and insisted that it was the government’s primary job to safeguard those rights. Thus our foreign policy began at the grass roots. It reflected the interests and dreams of ordinary Americans—individual freedom, financial well-being, personal fulfillment, greed—rather than reasons of state or dynastic ambitions. American officials felt obliged to permit and even support territorial and commercial claims made by their citizens, even when these trespassed on foreign lands or waters.

But Americans believe in something greater than the vectors of individual self-interest. For Kagan, the fundamental statement of American foreign policy is not Washington’s Farewell Address or the Monroe Doctrine but the Declaration of Independence, with its expression of universal ideals. In his view, the U.S. has always seen itself as acting not merely in its own interest but in the interest of mankind, claiming to bring modern civilization and the “blessings of liberty” to the nations we touch. Kagan quotes Lincoln’s Secretary of State, William Seward: “The rights asserted by our forefathers were not peculiar to themselves, they were the common rights of mankind.” Therefore, the United States had a duty “to renovate the condition of mankind” and lead the way to “the universal restoration of power to the governed” everywhere in the world.

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The Declaration set the standards of political legitimacy—the consent of the governed, and securing the rights of the governed—against which all other regimes were measured. Americans admitted that governments ought not to be changed for light and transient causes and that other peoples, in other cultures, might accept different forms of rule. Nevertheless, Americans tended to view non-democratic governments as transitory. Foreign regime change was not only possible but desirable. Indeed, American leaders thought change was inevitable once the liberal truths of the Declaration spread: the American Founders and their successors were in this sense progressives. Even a realist icon like John Quincy Adams, who famously explained that America “goes not abroad, in search of monsters to destroy,” believed in the primacy of ideology in international affairs and in America’s historic role in improving the condition of mankind.

Kagan explores in great detail the implications for foreign policy of that tragic deviation from the universal rights of the Declaration, the racial despotism of the slaveholding South. Slavery complicated and corrupted America’s mission. For nearly four decades American expansionism followed a stop-start pattern as the nation tried unsuccessfully to reconcile two antagonistic approaches to the world. The South sought and the North (by and large) resisted slavery’s expansion. The peculiar institution’s violent abolition was therefore a defining moment in the country’s foreign policy. It unleashed American power and removed the ambivalence and sense of hypocrisy caused by the union with slaveholders. Northern opposition to slavery was America’s first great moral crusade and war of ideological conquest.

The Spanish-American War was the next great endeavor. The U.S., to be sure, had self-interested reasons for going to war, including commercial interests in Cuba and the desire to ensure American preeminence in the Caribbean basin. The decision for war, however, was motivated primarily by public outrage over the Spanish government’s brutal policies in Cuba, which had caused an estimated 300,000 deaths, one-fifth of the island’s population. Yellow journalism might have stirred the pot but the truth was bad enough. Senator Henry Cabot Lodge, supposedly a cold-blooded realist, argued that the United States had a responsibility to defend the Cuban people against Spanish oppression. When Ambassador John Hay, another realist, famously called it a “splendid little war,” he was not trying to be ironic; he had in mind the war’s lofty purposes and accomplishments.

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Kagan rejects the standard divisions of the American foreign policy tradition into realists and idealists. He treats Hamilton and Jefferson as merely representing two different forms of liberalism. In his view, the dominant, default position of American foreign policy has always been “vindicationist”: i.e., America thinks it has the right and duty to bring liberty to the world. Kagan acknowledges an enduring tradition of “realist” criticism, warning Americans against arrogance, hubris, blind idealism, and imperialism. For example, Patrick Henry accused supporters of the Constitution of conspiring to turn the young republic into a “great and mighty empire.” Southern conservatives before and after the Civil War opposed foreign policy moralism, fearing it would be turned against domestic slavery or racial segregation. Mark Twain and the anti-imperialist movement opposed the acquisition of the Philippines. But in Kagan’s America, such warnings are a distinctly minor theme: Antifederalists, Old Republicans, Southern racists, Mugwumps, and other critics of an expansive foreign policy sometimes delayed or diverted history, but they rarely managed to steer the United States on a fundamentally different course. Universalistic liberal republicanism is too deeply rooted in the American DNA.

Kagan offers a striking, distinctive, and powerful account of the early history of American foreign policy. Placing the Declaration of Independence at the center of the story rings true. Dangerous Nation, when read together with Kagan’s prior studies of Central America and U.S.-European relations, makes the persuasive point that American military, economic, and ideological power has grown to the point where it is almost impossible for us not to intervene in the affairs of others. U.S. withdrawal or neglect of an international crisis is tantamount to choosing sides, and almost guarantees that we will revisit the crisis under even less auspicious conditions. Kagan’s story is a very good read as history, a stimulating and fresh look at events familiar and not so familiar.

Yet any monocausal explanation, however nuanced, has its limitations. Kagan looks for a key under a lamppost because that is where the light shines. His narrative bends to accommodate his thesis. He tends to conflate, for instance, the foreign policy views of Washington and Hamilton, as well as Lincoln and Seward, where the evidence suggests that there were important distinctions between the presidents and their advisors. He recounts many long-forgotten interventions—such as the dispute in the 1880s with Germany and Britain over Samoa—but dismisses long periods of American inactivity and self-denial as temporary aberrations caused by circumstances. These periods may have grown briefer as American power increased, but they are an essential part of the story, nonetheless. The United States has often paused, reflected, and accepted limits on its ability to influence events or promote liberty abroad. Individual citizens and congressmen may have wanted to intervene in favor of Greek, Hungarian, Polish, or Spanish-American liberation movements—but the U.S. government steadfastly resisted even non-binding official expressions of ideological support. The debate over slavery explains some but not all of that story. To understand American foreign policy in its fullest sense, there is still considerable value in multi-tradition accounts, such as those offered by Walter McDougall (Promised Land, Crusader State, 1997) and Walter Russell Mead (Special Providence: American Foreign Policy and How it Changed the World, 2001).

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In picking a fight with critics of an ideologically assertive liberal American foreign policy, Kagan chooses the ground most favorable to his case. Most realists, for instance, are not nostalgic about the lost age of a more modest America. They agree that American foreign policy, at least after the founding period, has been driven, alas, by abstract moral imperatives. Henry Kissinger, for example, following Lippmann and Hans Morgenthau, argues that America has swung wildly between the extremes of isolationism and international crusades, both of which have roots in liberal utopianism. Realism claims to offer a moderate ground between these poles, to provide policy ballast that recognizes the limits of power, the realities of international politics, and foreign cultures’ resistance to change. During the 1930s, 1940s, and 1970s, when the Eurasian balance of power was under threat, realists urged the United States to become more active in global affairs. Today, with America apparently at one of its interventionist extremes and widely viewed as the principal threat to international security, realism urges a more modest agenda in our own interest, and in the interest of human liberty.

The challenge for those like Kagan who favor an assertive liberal foreign policy is to demonstrate that liberal principles themselves—not the realists’ dependence on external limiting forces, or a sense of historical tragedy—offer a superior practical and moral guide to statecraft. Kagan seems reluctant to engage in a critical discussion of first principles. When he summarized his “dangerous nation” argument in the New Republic, he acknowledged that “whether a different kind of international system or a different kind of America would be preferable is a debate worth having. But let us have this debate about our future without illusions about our past.” But he begs off the decisive debate—or declares it irrelevant. America is what it is and what it always has been. Get over it. “Today many hope and believe that the difficulties in Iraq will turn Americans once and for all against ambition and messianism in the world,” Kagan wrote recently in the Washington Post. “History is not on their side.”

But why should those who favor a more modest foreign policy—or a different America—concede the point that history is against them? Kagan’s own narrative is hardly triumphalist or uncritical. Native Americans were treated brutally. Reconstruction, like many other American experiences with democratic nation-building, proved deeply disappointing. The Spanish-American war led to a most unsplendid conflict against the Filipinos, and a frustrating occupation of Cuba that left lingering resentments. Kagan acknowledges a parallel between the Alien and Sedition Acts and the illiberal anti-Communist excesses of the 1940s and 1950s. His young America often appears immoderate and not particularly appealing; in fact, much of his text could have been written by a realist or radical critic of the American regime. Although his honesty does him credit, it hardly dispels the arguments of those today, at home and abroad, who fear a dominant, or domineering, America.

To answer these arguments may require a closer examination of the American foreign policy tradition to isolate the statesmen and principles of action that best represent what Kagan calls the founders’ practical idealism. Not all aspects of modern liberalism—and Kagan’s presentation of liberalism is decidedly modern—are created equal or are equally capable of guiding our relations with the rest of the world. The Declaration, Washington’s Farewell Address, John Quincy Adams’s July 4, 1821 address, the Monroe Doctrine, Lincoln’s Kossuth Resolutions, and other important statements of American foreign policy are meditations on moderation as well as on our responsibility to the rest of mankind. In these and like instances, universal principles did not supersede the facts of geography and power, the need for circumstantial judgments of costs, risks, and opportunities, or the value of according a decent respect to the opinions of mankind. Early American progressivism is not necessarily the same as 20th-century progressivism, in which liberalism becomes something of a categorical imperative.

Kagan has the insight to come to grips with these fundamental questions. His second volume offers him the opportunity to do so.