Henry Nau must have resisted the urge to write “I told you so” in the new preface (2015) to this paperback edition of his fine study of America’s foreign policy principles. His 2013 book argued that America has been most secure, prosperous, and true to her ideals under presidents who blended realistic and idealistic views in a strategy of peace-through-strength. Nau calls this “armed diplomacy” serving a prudent internationalism. He had warned during President Obama’s first term against retrenchment from military efforts to shape our security environment, and global events already had vindicated Nau’s warnings by 2013; but a cascade of subsequent problems overwhelmingly makes his case.

American ideals, interests, and long-term security have suffered during the second Obama term because of a doctrinaire adherence to the first-term strategy of restraint, distancing from allies, and defense cuts. We now see that Senator Obama campaigned, in effect, to meet the public’s lowest expectations of America’s role in world affairs, when public opinion was in a sour, insular mood. In seven years, President Obama has driven us lower than nearly anyone expected, perhaps even he. Precipitously withdrawing from Iraq, half-withdrawing from Afghanistan, passively observing or abetting the rise of extremist Iranian power (soon to be a nuclear power, thanks to the president’s dovish diplomacy), and permitting a Sunni Islamist caliphate in what used to be Iraq and Syria—the president has achieved all that just in the greater Middle East. The Obama doctrine of retrenchment from American commitments, and diplomacy for diplomacy’s sake, also has been intransigently passive as Russia invaded and occupies Ukraine and now (with its partner Iran) dominates Syria; as the European Union becomes nearly overwhelmed with crises; as Turkey (a NATO ally) slides toward Islamism; and as China builds a new kind of aircraft carrier—from artificial islands—in the South China Sea. It turns out that risk-avoidance, and leading safely from behind, are risky and unsafe.

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America has undertaken, in the past two decades, a severe oscillation from international hyper-engagement under President George W. Bush to President Obama’s hyper-restraint. Nau knows that America occasionally has inflicted such pendulum swings on itself, so he seeks to recover an underappreciated tradition that has held a successful middle ground. His book is both a scholarly contribution to theories of international relations and foreign policy, and a timely aid to policy debates as we consider how to recover from the Bush-Obama cycle.

A professor of political science and international relations at George Washington University, Nau asks us to rediscover America’s founding principles about war and peace, and a tradition of American statesmanship up to the Reagan presidency that adapted those principles to new threats and opportunities. This approach is fairly rare among scholars and pundits, who mostly ask us to get over this whole American thing. The realist school at one extreme tells us to forget our supposedly distinctive view that universal natural rights should govern political action, at home and abroad. The opposite extreme of liberal internationalism tells us to forget our national interests and distinctive power; we must join the only legitimate vision, under the new sovereignty of international law and institutions and gentle diplomacy. Realists thus reject internationalism and would have us consult only our interests, and the interests and power of other states (think of Richard Nixon in his darkest moments). Liberal internationalists admonish us to think only of justice, and the legitimacy of subordinating our power to global governance (think Woodrow Wilson, or Jimmy Carter before he recovered his senses). Nau knows there also is a nationalist strain in American foreign policy, which, unlike these schools, believes in American exceptionalism. We launch distinctive principles of justice into the world, and while we don’t perfectly embody them, we try to foster the circumstances and power to best preserve them at home and internationally. For nationalists, this usually means siding with realists and minding our own business unless attacked. But when attacked, the U.S. tends to lash out fiercely, as in our reactions to Pearl Harbor and 9/11, or in General Andrew Jackson’s storming of Florida in 1818.

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Nau turns to the words and deeds of Presidents Thomas Jefferson, James K. Polk, Harry Truman, and Reagan to discover an alternative tradition that blends elements of these approaches into a distinctively American foreign policy avoiding the extremes of over-extension and retreat. The Polk and Reagan case studies most persuasively capture “conservative internationalism.” Truman is a good but imperfect fit (occasionally succumbing to liberal-internationalist utopianism). The Jefferson case is weakest, but if one focuses (as Nau does) on the Barbary Pirates war, and his bold diplomacy to double the republic’s size with the Louisiana Purchase, then Jefferson could qualify. This Jefferson could join the other three presidents in confronting President Obama, and those who defend his record today, with Nau’s query: “Is it possible to be too modest and restrained in foreign affairs, just as it is possible to be too ambitious and aggressive?”

The book argues that America can recover a sober middle ground by being internationalist in an American sense, assuring our security by shaping global affairs toward our principles of peace, commerce, individual rights, and free regimes. Given nuclear weapons, ballistic missiles, cyber attacks, and trans-national terrorists exploiting all means and targets, prudence requires greater international vigilance and presence. This internationalism would be conservative because grounded in the American traditions of natural rights, limited government, religious liberty, and awareness that government power is necessary to protect freedom in a dangerous world. Armed diplomacy thus comes to the fore, with a blend of statesmanship and public rhetoric. No sober American would accept the utopianism of liberal internationalist theories about global law and institutions providing collective security, or believe that all peoples are ready for democracy as we might practice it, or think we can safely mind our own business, ceding initiative to freedom’s enemies, and mothballing our global military readiness until attacked. America’s conservative internationalism grasps that “diplomacy without the use of force does not reduce the role of arms in world affairs; it simply enables the use of arms by despots.”

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Nau combines historical study of these presidents with an outline of a post-Obama grand strategy to argue that conservative internationalism could again mitigate America’s gyrations from liberal internationalism’s hubris and over-extension to the retrenchment of realism and nationalism. Seen through this lens, Obama’s policy actually blends elements of realism and nationalism with liberal-internationalist hopes for diplomacy, yielding a lowest-common-denominator formula for reducing America’s global military commitments.

From his model presidents Nau gleans that the American blend of interest and ideals must accept incrementalism: we can plausibly expand the zone of freedom, peace, and commerce only near existing liberal democracies (an “inkblot” strategy). For this distinctive strategy, both force and ideals have limits. Thus force and diplomacy always must work in tandem, so that military intervention does not overestimate its capacity to achieve lasting change, and diplomacy does not overestimate its capacity to secure peace or other liberal aims without force in support. American strategy cannot expect to spread liberal democracy to every culture; we must settle for stability in some regimes and regions around the world.

This conservative blend is a much-needed corrective to America’s predominant debates about grand strategy across recent decades. The other schools don’t explain America, this distinctive republic rising to be the world’s dominant power but not a traditional empire. Nau’s argument would be strengthened, however, by seeking the deeper roots of this balance of sobriety and idealism, including in George Washington’s grand strategy. Nau follows the conventional identification of Washington as a nationalist or isolationist. But in fact, he urged that we balance our interests with principles of justice, employ temporary alliances until we had become “a great nation,” and avoid permanent alliances that would subordinate our young republic. There is a clearer line from Washington to Truman and Reagan than from Jefferson to them. Nau is right to look to our founding era, but Jefferson’s blunders should be weighed against his strengths. As his presidency ended, America had little federal military force. This invited British bullying, and soon thereafter led to the War of 1812, including the 1814 British sacking of our capital. After the war, Jefferson seemed to recognize the error of his ways, when he reversed himself on the constitutionality of a bank that was necessary to support national security. Still, the original Jeffersonian spirit of military minimalism is surging through the land today, so Nau’s thesis is helpful in provoking us to reconsider the enduring relevance of old debates.

Nau’s classical-liberal theory of conservative internationalism, with its sober idealism, deserves a central place in our debates about how to restore our security, including the liberal global order America had built to protect our interests and ideals. Conservative Internationalism should be required reading for the foreign policy and national security staffs of every serious presidential campaign, Democratic or Republican.