Donald Trump’s critics, at home and abroad, accuse him of breaking down the rules-based international order that the United States built over the past eight decades. The president’s substitute, they allege, is an erratic, bad-tempered, xenophobic, beggar-thy-neighbor nationalism that aligns with his authoritarian and populist counterparts overseas, all pointing a conflict-prone world toward fascism, crony capitalism, and environmental disaster.

Colin Dueck, professor at George Mason University, disagrees. In Age of Iron: On Conservative Nationalism, Dueck continues his efforts to understand America’s foreign policy traditions, and to articulate a sound course for the future. The American nationalism he advocates is neither fascistic nor undemocratic, being compatible with American engagement overseas that defends and promotes democracy. The recent rise of a distinctive American nationalism is based on domestic and international factors much larger than Trump, Dueck contends, so it won’t disappear when the president leaves the scene.

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Age of Iron examines how republican foreign policy ideas developed over the past century. Dueck identifies three persistent tendencies: noninterventionist, hardline unilateralist/nationalist, and conservative internationalist. No one approach has ever completely dominated. Instead, presidents and party leaders have melded the elements to account for changing political and strategic circumstances. In particular, all were reactions against, adaptations to, or corrections of, liberal or progressive internationalism.

World War I marked the beginning of conservatism’s encounter with progressive internationalism. Prior to Woodrow Wilson’s presidency, according to Dueck, the mainstream U.S. foreign policy tradition was American nationalism. It valued the strict preservation of American national sovereignty and encouraged republicanism, preferably by example, but also through U.S. territorial and commercial expansion. Seeking diplomatic and strategic latitude, it rejected entangling alliances but cooperated with other nations when doing so advanced American interests.

Wilson offered a fundamental alternative to this nationalist tradition: a new world order characterized by global democratic government, economic interdependence, mutual disarmament, and collective security. Only through new global, binding, multilateral commitments could liberal values be served. The cornerstone was a League of Nations, in which every member state would promise to protect the independence of every other state.

Virtually all Republicans rejected this open-ended commitment, but for different reasons. Some argued for peace, disarmament, nonintervention, and strict disengagement. Hawkish or hardline unilateralists endorsed robust national defenses and firm responses to any intrusion on the nation’s honor, while remaining apart from Old World hostilities or alliances. Conservative internationalists endorsed vigorous responses to German aggression through a postwar alliance with France and Great Britain, without making any sweeping commitments to worldwide collective security. Because Wilson stubbornly refused to compromise, the nation he led never joined the League he created.

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But out of that debate the three conservative schools of thought emerged. First, noninterventionists (who often are libertarians) oppose U.S. military commitments overseas. Many members of this school do support commercial opportunities and diplomatic engagement with other countries. But their defining feature is a deep resistance to American military intervention, bases, and alliances abroad.

Second, conservative hardliners place maintaining American sovereignty above all other considerations. In practice, this means maintaining very strong defenses, punishing any threat to U.S. citizens severely, refusing international accommodations, and otherwise limiting multilateral commitments. They have no objection to using force when necessary, and are characteristically ferocious when they see their country threatened. Yet their instinct in most circumstances is that when it is not necessary to intervene overseas, it is necessary not to intervene.

Third, conservative internationalists believe in a more active U.S. international role—economically, militarily, and diplomatically. They differ from their liberal counterparts in placing less emphasis on multilateral institutions.

In political terms, rejecting the League of Nations was essentially a victory for unilateralists and noninterventionists, who dominated the party for the next two decades. With the rise of the fascist threat and the outbreak of World War II, conservatives divided once more. On one side, internationalists such as Henry Stimson, and some hardliners, advocated U.S. aid to Great Britain against Nazi Germany. The other side, represented by such diverse figures as former President Herbert Hoover, Senator Robert Taft of Ohio, and aviation hero Charles Lindbergh, argued for an “America First” policy of avoiding measures that might lead to American involvement in this new European war. The Japanese attack on Pearl Harbor settled that debate in favor of the internationalists, marked by the conversion of one-time hardliners like Senator Arthur Vandenberg.

The second wave of progressive internationalism, developed under Franklin Roosevelt and Harry Truman, included the Atlantic Charter, United Nations, and creation of a new international economic order. But their internationalism differed from Wilson’s in seeking bipartisan support at home while conditioning greater American engagement overseas on geopolitical realities.

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This was especially true once the Soviet threat emerged. That enemy established conservative internationalists’ primacy among Republicans, especially with the election of Dwight Eisenhower to the presidency in 1952. Hardliners like Taft resisted permanent entanglements in Eurasia and the expense of a massive military establishment. What tipped the balance and eventually united the party was anti-Communism, to which the hardliners wholeheartedly subscribed. Subsequent Republican presidents, conservative internationalists all, sought to adapt the Democrats’ progressive framework to serve American interests. The manner in which they did so varied considerably from one president to the next. All, save perhaps George W. Bush, were parsimonious in the use of force, skeptical about the ability to engineer social change in the world, and anxious to shift more of the burden of defense onto allies.

Vietnam caused the Democratic Party to shed Roosevelt and Truman’s hard-headed geopolitics. The subsequent demise of the Soviet bloc seemed to open up the possibility once again of a progressive world order. The third wave of progressive internationalism combined multilateral institutions, conflict resolution mechanisms, humanitarian interventions, worldwide democratization, and global governance projects, all of which were touted to render traditional patterns of power politics irrelevant. America should emphasize soft power, avoid unilateral action, and coordinate interstate compromises through global institutions. The United States, in turn, would accommodate itself to global norms, at home as well as abroad, in order to encourage greater international cooperation.

In Dueck’s opinion, many (but not all) Republican internationalists, although more realistic about the limits of multilateralism, were swept up in this enthusiasm about globalization and the promotion of democracy. Most conspicuously, the George W. Bush Administration responded to 9/11 by embracing ambitious attempts to democratize the Middle East. But the Communist threat’s disappearance also saw, as early as 1992, the reemergence of noninterventionists and hardliners, such as Rand Paul and Patrick Buchanan. As a candidate in 2000, Bush himself had emphasized a more restrained international posture. Most hardliners rallied behind him after 9/11 but soon became frustrated with the Iraq War and Bush’s freedom agenda. Once Bush left office the party again splintered into its most basic divisions.

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In 2016, according to Dueck, insurgent candidate Donald Trump did what had previously seemed impossible. His provocative “America First” slogan upended the internationalists in favor of the other two dispositions. In part, this reflected the Republican Party’s profound shift toward populism, cultural conservatism, and white working-class voters. His newly empowered populist supporters had policy preferences irreconcilable with those of orthodox conservatives, especially on key economic issues.

Dueck contends that the Trump phenomenon, in foreign policy terms, is best understood as a reaction against the third wave of progressive internationalism, to which Trump believed the party’s political class and intellectuals had largely succumbed. He appealed to the hardliners by calling for harsh measures against jihadist terrorists and ISIS, and for an end to uncontrolled borders. He favored increased defense spending but opposed endless wars. Trump demanded that U.S.-allied trading partners no longer free-ride off American security guarantees and lopsided commercial arrangements. Newt Gingrich once accused Robert Dole of being the tax collector for the welfare state. Trump, in effect, accused George W. Bush and his supporters of enabling the progressive project, destructive at home and abroad.

Dueck is one of the relatively few scholars, including Walter Russell Mead, Mackubin Owens, and Niall Ferguson, who take Trump’s foreign policy seriously, however much they may criticize particular actions of his.

Although Trump ran for president as an unabashed America-Firster, Dueck argues that the actual practice of his administration has been a unique hybrid of all three Republican tendencies. He cracked existing orthodoxies and opened up previously latent foreign policy options. Dueck concludes that the Trump Administration, not unreasonably, is attempting to recalibrate American interests to account for a new era of intensified great-power rivalry, resurgent nationalisms both authoritarian and democratic, popular skepticism regarding the benefits of globalization, shifts in focus from the Atlantic to the Pacific, and challenges to American primacy.

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Despite his early rhetoric, Dueck points out, Trump has dismantled neither America’s alliance system nor its forward presence overseas. He has pushed U.S. allies hard on defense spending and trade, openly challenging internationalist assumptions. Yet the Trump Administration continues to pressure foreign adversaries, more in some cases than the Obama Administration did. Trump insists that he only wants to terminate or avoid endless wars.

In terms of diplomatic style, according to Dueck, Trump is not determined to destroy what progressives describe as the “rules-based world order.” Nor is he committed to upholding it. Rather, he looks to pull existing arrangements in the direction of material U.S. interests, and is open either to renegotiating or abandoning those arrangements on a case-by-case basis.

As Mark Twain reportedly said of Richard Wagner’s music, Trump’s foreign policy is better than it sounds. Still, Dueck expresses three main areas of concern regarding the president’s approach. First, though the president is understandably responding to domestic concerns about the detrimental effects of trade deals, he may have gone too far in correcting them, especially by not differentiating between allies and adversaries like China. For Americans as a whole, international trade promotes innovation, exports, and export-related jobs. Second, Trump’s pressure on allies to increase their military spending, hardly new, will be neither healthy nor productive if taken too far. If the United States were to give the impression of disengagement or intense ambivalence in relation to core alliance commitments, authoritarian aggressors might exploit what they perceived as vulnerabilities.

Third, Dueck finds the most fault with the president’s management style. Trump clearly is prepared to make bold foreign policy decisions. The question remains whether the execution of those decisions is characterized by clarity, steadiness, and adequate information as to the necessary specifics. It is still far from clear to Dueck that Trump understands the basic purposes of America’s foreign policy and national security bureaucracy, and how to utilize them in pursuit of his own agenda. He too often approaches major foreign policy issues, meetings, and decisions with unconcealed disdain for the need to master the details. But no president can literally manage the U.S. foreign policy process alone, or purely on instinct. If a president signals mixed messages or unpredictability regarding core commitments, as Trump sometimes does extemporaneously, aggressors may eventually press their advantage.

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If anything, Dueck understates this point. For a recalibration of American interests to succeed, it must be bureaucratized. This means clear goals, good planning, and consistent execution. To be sure, even in the most effective administrations, policy involves a great deal of sausage-making and staff turmoil. Strategies must change to meet emergent circumstances. In the first year of the Trump presidency, smart and experienced staff members at the National Security Council and the Department of Defense put together National Security Strategy and National Defense Strategy documents that formulated coherent objectives and strategies. They were acknowledged as being serious efforts even by those who opposed Trump and his policies. Vice President Mike Pence and Secretary of State Mike Pompeo have put these ideas into the public forum.

But it does not appear that those plans are being pursued systematically, at least on the political-military side. Trump may blame the deep state or the establishment, but it is difficult for even the most loyal staffer or civil servant to guess what is in the president’s mind at any given moment and then translate that guess into actions the president might not immediately disown.

Critics would say that the lack of consistent goals and implementation is not merely a case of a badly flawed management style, but of Trump’s badly flawed, corrupt character. This goes beyond his erratic decision-making. Corruption in foreign policy leads straight to domestic corruption. Democratic politicians, journalists, and professors have belabored this accusation since the 2016 election. But to those who might be called conscience conservatives—not just Never Trumpers, unrepentant establishment internationalists, and neoconservatives—the accusation largely rings true, especially over the matter of Ukraine.

As a result, the pool of those able and willing to serve in foreign policy positions, and implement a necessary course correction—and just as importantly, to defend that correction publicly—is small and shrinking. They do not want to be hauled before Congress or the courts. They are reluctant to engage the media and academia, finding themselves compelled to defend Trump’s character rather than to assess his policies. Dueck might say that even if one despises the messenger, one must not despise the message. The counter is that the messenger matters a great deal when he is in a position to muddle or even negate the message.

For example, there are good reasons for conservatives to debate the strategic wisdom of military and political support to Ukraine and continued engagement in the Syrian civil war, to challenge the bureaucratic and establishment resistance to policy changes that conform to the Trump Administration’s concept of the national interest. But the necessary recalibration of that interest has been made much more difficult because it has become confused with Trump’s personal interest.

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For Dueck, the long-term future of Republican foreign policy will require balancing internationalist, hardline, and noninterventionist concerns. He apparently believes that the Trump hybrid itself is not sustainable beyond his time in office, in large part because of the president’s unique personality. Still, the domestic and international factors that brought it about will persist and must be accounted for. Dueck seems to be looking at a time when Trumpist foreign policy is discussed apart from Trump himself, and thinking through how to reconcile the hardline unilateralists with a revived, reformed conservative internationalism.

The unifying theme would be that nationalism, rightly understood, opposes an increasingly radical progressive internationalism. Dueck’s nationalism is a democratically oriented and civic form of patriotism: a love of a particular place; maintaining that the world is best governed by independent nation-states; and that only within the context of such states can a free citizenry experiment with constitutional forms of self-rule. Conservative nationalism would focus on preserving and promoting the country’s interests, rights, values, security, traditions, and way of life, believing it is entirely legitimate to do so.

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What would define a conservative nationalist foreign policy? For Dueck, it begins by distinguishing the useful elements of America’s internationalist legacy, a process Trump has started. On balance, American national interests have been well served by a U.S.-centered alliance system that deters major authoritarian adversaries. This alliance system involves an underlying U.S. forward presence to maintain regional balances of power. The United States should pursue regionally differentiated strategies of attrition, assertive containment, and peace through strength. Such an approach also requires clear, credible deterrent threats.

Dueck also favors responsible balances on trade policy that don’t dismantle relatively open trading arrangements with U.S. allies. Among other steps, the United States should consider reentering a revamped Trans-Pacific Partnership, one of the most effective ways to resist Chinese economic influence within the Asia-Pacific.

So far, this sounds like the old conservative internationalist playbook. What would allow hardliners to embrace such an approach? As anti-Communism once brought the factions together, conservatives of all stripes should unite around the need to combat the progressive project to subordinate American national sovereignty to global multilateral arrangements. And even many progressives are beginning to acknowledge the Chinese threat, another point around which to rally conservatives.

Above all, for Dueck, there would be an explicit commitment to the national interest, and no binding multilateral commitments for their own sake. Rules and agreements must advance, and never hinder, American security and prosperity, while never compromising our sovereignty or democratic self-governance. Controversial domestic social issues would be resolved by domestic and democratic processes, rather than through the backdoor of international jurisprudence. The United States would speak up on behalf of democracy and democratic movements, and aid existing democracies, but would not prioritize regime change. Dueck reminds the noninterventionists and the critics of endless wars that Republican presidents have historically been reluctant warriors, cautious in resorting to armed intervention, and disinclined to see the military as a tool for social or political transformation. (George W. Bush is the one obvious exception.)

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Ultimately, we must ask what kind of people we are…if we are a people at all. Progressive internationalists contend that nationalism of any sort encompasses all the bad features of Trumpism. Thus, it must be fought at home and abroad through international norms, redistributionist economic policies, and identity politics that transcends borders. The anti-Trump conservatives would argue that Dueck fails to distinguish adequately between Trump’s bad nationalism and good nationalism, thus enabling his bad behavior. But conservatives of all stripes have yet to agree on what defines good nationalism, or whether nationalism adequately captures what makes the American regime exceptional. These fundamental questions will require hard work.

If there is to be a coherent, consistent Republican foreign policy after Trump, whether his presidency ends in 2025 or before, there will need to be some synthesis of the various schools of thought, even if there is not perfect agreement. Even if one credits Trump for heading in the right direction, he has divided one-time friends, and lost many who might have been friends, including some Democratic thinkers who still recognize hard power’s importance. In fairness, the “conscience conservatives” sometimes disdain those who, out of sincere prudence, have chosen a different course—which includes the vast majority of ordinary Republicans and many independents. President Trump may prove to have been a necessary catharsis. But those seeking to formulate policy in the aftermath of that catharsis face profound challenges. Colin Dueck’s Age of Iron is an excellent start to the work that lies ahead.