Modern architecture begins with blueprints and moves towards concrete. Cathedrals, in contrast, are feats of ongoing improvisation, not grand design. Buttresses are added; naves removed. Purposes shift. Hagia Sophia served Byzantine Christianity, the Church of Rome, and later became a mosque. Cathedrals collapse but can also rise from the ashes, as Notre-Dame today demonstrates.

The cathedral metaphor helps us to rethink international order and its renewal. We often describe the current world order as an architectural blueprint, designed by enlightened statesmen as the Second World War came to an end. This is our ‘liberal world order’, our ‘rules-based international order’, or ‘the world America made’.

Today, however, we fear the architecture is crumbling. Geopolitical rivalries are resurgent; liberal democracy is in retreat. Globalisation is reversing, protectionism rebounds. The echoes of the 1930s reverberate, but we face threats Winston Churchill’s generation did not: thermonuclear armageddon, ecological collapse, and even potential conflicts with our mechanical progeny.

If international order results solely from architecture, we might worry that renewal will follow only after the wrecking ball of major war demolishes the crumbling structure. The dates commonly cited as the founding of international orders – 1648, 1714, 1815, 1919, and 1945 – all mark the ends of devastating wars.

Yet, the cathedral metaphor suggests the possibility of renewal without catastrophe. Cathedrals evolve and adapt while remaining recognisably cathedrals. International order, too, can renew itself through improvisation rather than collapse. This metaphor captures historical reality more accurately than modern architectural imagery. International order rarely emerges from singular acts of creation; it results from continuous improvisation, adaptation, and renewal.

The Atlantic Charter of August 1941 offers a plausible point of departure; it articulated ideals that would motivate the postwar world. These included liberal commerce, self-determination, and the collective resolution of disputes.

Wartime conferences gave these precepts institutional form. Building upon the League of Nations, Dumbarton Oaks envisioned a new international organisation to represent nation-states and resolve their disputes. Bretton Woods conceived an International Monetary Fund (IMF) that would superintend a general return to currency convertibility and liberate governments from the rigidity of the old gold standard.

Two great tensions shaped the resulting international order. The first involved hegemony and multilateralism. The second involved sovereignty and interdependence.

At the heart of the first question was the role of the United States. While critical historians have often emphasised America’s desire to dominate, the reality is more complex. Americans in the early 1940s were divided. Some envisioned a global destiny. Others anticipated postwar demobilisation and strategic retrenchment. Some hoped to tutor the world in modernity.

At the heart of the second question was the willingness of governments to defer to universal norms. The UN Charter encapsulated this tension: it made universal human rights an aspirational standard and affirmed the absolute territorial sovereignty of nation-states. Similarly, the IMF sought to restore an integrated world economy, but gave countries broad latitude to control their economies in pursuit of national goals. What resulted from wartime design, we might surmise, was aspiration and paradox more than coherent architecture.

The fate of world order, in practice, hinged upon American volition. The United States in 1945 produced 60 per cent of the industrial world’s output and most of its oil. It also commanded the world’s only nuclear weapons.

What would Americans do with this vast opportunity? Recent history had taught US political elites hard lessons. Their failure to join the League of Nations, some reasoned, had doomed the last great initiative in world ordering. Many voters agreed. Wartime opinion polls indicated robust public support for the United Nations.

The depth of this conversion should not, however, be exaggerated. Americans had not experienced the war’s devastation as Europeans and East Asians had. Aside from those who served overseas, few Americans had ever travelled abroad. The nation’s cultural outlook remained parochial: in 1940, 40 per cent of the US population remained rural – twice the British level.

The paramount concerns for the US government in 1945–46 were domestic. Top priorities included demobilisation, the reconversion of the wartime economy to peace, and avoiding the economic turmoil and labour unrest of the 1930s.

Reflecting these priorities, Congress acted swiftly after VJ Day to put Americans first, terminating Lend-Lease aid to wartime allies within weeks. Preoccupied with domestic issues, US policymakers showed sparse concern for the needs of others.

When John Maynard Keynes visited Washington in December 1945 to plead for a massive loan, an administration wary of congressional reactions offered $3.75 billion at two per cent interest, and extracted painful concessions in return. These conditions included dismantling imperial preference, a condition that drove a nail into the coffin of the British Empire.

In the late 1940s, the United States fabricated an international order quite different from the world policy that planners had conceived in 1944-45. The wartime design envisioned an institutional order of planetary scope. The postwar reality was a hierarchical order, enacted only in one portion of a world divided. Call it the Pax Americana. What made it possible was the Cold War.

Wartime planners had expected the USSR to participate in postwar institutions. Reality bit in late 1945, when Soviet diplomats announced that the USSR would not join the IMF. The decision shocked the US government, prompting the State Department to request the explanation that became George Kennan’s famous Long Telegram.

Hereafter, East-West estrangement motivated escalating US commitments to allies and clients. These took the form of security assistance, trade concessions, and development aid. What made this largesse politically possible was the galvanising power of anti-communism. To garner votes for Cold War initiatives, including the Truman Doctrine and the Marshall Plan, President Truman impressed upon voters the urgent necessity of confronting Communism in Europe.

These early commitments were immense, but the United States did not consecrate the Pax Americana until it concluded the North Atlantic Treaty Organization (NATO) in early 1949. This peacetime alliance – unprecedented in American history – sealed the new order. The United States had improvised an international order quite different from the one previously envisaged.

NATO established a new kind of international order: a hierarchical alliance in which the United States assumed unprecedented responsibility for the security of subordinate states. Nothing affirmed its novelty as much as Washington’s nuclear umbrella. Responsibility for territorial security – a classic attribute of modern sovereignty – passed from the client to the superpower.

Yet NATO was a regional alliance, not a universal design. In East Asia, a different kind of order emerged, organised around bilateral treaties rather than multilateral guarantees. Here, US policy contested Cold War frontiers that were murkier than Europe’s. To prevent communist encroachment, the United States cultivated client states: South Korea, South Vietnam, and Taiwan.

The relationship of these states to the United States – independent yet dependent – defined the nature of the international order that emerged from the late 1940s. The Pax Americana was not an extractive empire but a league of nation-states, nominally sovereign yet reliant upon American protection and support. If the edifice is compared to a cathedral, Washington’s nuclear umbrella was its rib roof: a protective carapace and a source of structural cohesion.

Distribution bound the Pax Americana together. To secure the Free World, goods flowed outward from North America: security, finance, and technical aid. Allies benefitted, and the result was the consecration of an international order centred upon the singular power of the United States.

The Pax Americana was never stable; it experienced constant reinvention. Nuclear deterrence illustrates this dynamic. During the 1950s, the emerging risk of mutual assured destruction hollowed out the credibility of American guarantees. Giving allies operational control over tactical nuclear weapons provided a stopgap solution but did not resolve NATO’s fundamental dilemma: would Washington really risk Chicago to save Paris?

By the late 1960s, moreover, Washington and Moscow were collaborating to curtail the sharing of nuclear weapons technologies with non-nuclear states. Their efforts advanced non-proliferation, but also upended the logic of Cold War order. Some critics sniped that a new divide between the superpowers and the rest was replacing the old East-West binary.

Allies responded in different ways to the Pax Americana’s transformations. British policy after the Suez Crisis clung tightly to Washington; French policy aimed to maximise autonomy. As these two countries acquired their own nuclear arsenals, their doctrines reflected this divergence. The British tethered their deterrent to Washington’s; the French built an independent force de frappe.

Few observers grasped the debilities of an international order centred upon the United States with the acuity of Charles de Gaulle. From 1958 onward, De Gaulle proposed to remake the West as a trilateral directorate in which Great Britain and France would participate equally. Receiving no satisfactory response, De Gaulle instead pushed throughout the 1960s to maximise French autonomy within the Western alliance.

NATO in the 1960s experienced challenges within the United States, not just internationally. Crucially, the domestic consensus for US international leadership was never robust. Had Eisenhower not taken control of the Republican Party in 1952, the alternative might well have been an early US withdrawal from NATO.

Eisenhower’s immense contribution to postwar order was to build a bipartisan ‘consensus’ around American internationalism that endured, more or less, into the 1980s. But this consensus was never as secure as it might appear in hindsight. Congress in the late 1960s came close to defunding US troop commitments to NATO. The Democratic Party in the early 1970s nominated a presidential candidate who called upon Americans to ‘come home’ from the world.

Such episodes remind us that durable American internationalism remained, in many ways, an improbable proposition. Since the late 18th century, American policy had sought to distance the United States from Europe, not dominate the world. Nor had the United States evolved the institutional capacities of a great power. Rather, Americans had improvised a national security state in the late 1940s, often borrowing from British models: the Chiefs of Staff Committee, the British War Cabinet, and the Secret Intelligence Service (MI6).

Debilities of institutional capability and political will beset the American order from the outset. What made the Pax Americana possible at mid-century were the vast margins of material advantage the United States commanded. Washington in 1945 had money; Europeans and East Asians did not.

During the quarter-century after 1945, however, Europe’s and East Asia’s economies recovered from wartime trauma. One result was the destabilisation of an international order predicated upon absolute American primacy. The consequences included balance-of-payments crises that bedevilled the US dollar in the early 1970s. Put simply, the Pax Americana improvised in the late 1940s had become unstable.

The 1970s brought crises and improvisation. A major dollar crisis in 1971 prompted a reorganisation of the monetary system created at Bretton Woods. First, the United States abandoned the gold standard. Next, IMF members abandoned fixed exchange rates and loosened controls on capital flows. The result was surging cross-border lending, ushering in a new era of globalisation.

The energy crisis of 1973–74 confirmed the pattern: the world economy was integrating rapidly, eroding the policy autonomy of nation-states. What economists called ‘interdependence’ made ineffectual the Keynesian tools that governments had previously used to stimulate growth. Stagflation instead gripped industrialised societies.

The turmoil of the 1970s prompted political creativity: the G5 convened at Rambouillet in 1975 and became the G7 the following year. These summits became annual conclaves in which leaders sought common solutions to common problems. Some, including President Carter, argued that managing shared economic challenges could revitalise the West. Such revitalisation became imperative as Soviet-American détente in the 1970s dulled the Cold War hostilities that had formerly bound the West (and the East) together.

Promoting human rights and democracy also became a new source of common purpose for the West in the 1970s. Largely absent from international diplomacy in the two decades after the Second World War, the assertion of human rights emerged prominently among American presidents such as Jimmy Carter and Ronald Reagan. European leaders also explored these possibilities, inserting human rights commitments into the Helsinki Final Act of 1975. This intervention forced the East Bloc to accept human rights standards – and helped, over time, to bring the Cold War in Europe to an end.

The Cold War’s ending produced no reordering of world politics akin to what the ends of previous great wars had produced. Unlike in 1815, 1919, and 1945, prewar structures, such as NATO, endured. The continuities outweighed the changes, which amounted to little more than modest reductions in defence expenditures.

Official Washington in the Cold War’s aftermath did not rethink the national security institutions and assumptions adopted in the late 1940s, at least not in a fundamental way. Rather, US policy endured in a familiar pattern, which 9/11 confirmed. With the proclamation of a Global War on Terror, the United States led an alliance of nation-states against an ideological foe.

Striking as the continuities were, deep and consequential changes had occurred in the late 20th century. One set of changes involved the geopolitical logic of world order; the other, its material wellsprings.

The Pax Americana had been a creation of the early Cold War, founded by leaders who saw grave danger in world Communism. The international order they built comprised two wings: a European wing, under NATO, and an East Asian wing, organised around hub-and-spokes alliances. All hinged upon Washington’s nuclear umbrella – unfurled within geographic limits.

With the Cold War’s end, the American-led order lost its earlier geopolitical logic. Americans could no longer define their relationship to Russia – or to China, for that matter. Were these great powers-adversaries, whose implacable hostility buttressed the West’s order, or had Russia and China become candidate members of the ‘liberal world order’.

Had the United States, by implication, become history’s first planetary hegemon: superintendent of an international order that now enveloped the entire world? Unable to define the scope of their responsibilities, US leaders struggled to distinguish between core and peripheral priorities. As a result, NATO found itself undertaking military operations in the Balkans, then in Afghanistan.

The second immense change involved the Pax Americana’s material dynamics. The Cold War order built in the late 1940s had functioned as a distributive system, wherein resources flowed outward: from the United States, to allies and clients. The singular prosperity of the US industrial economy at the 20th century’s midpoint made this system work, sustaining an international order based upon the United States’ assumption of a disproportionate share of the responsibilities.

Between 1950 and 1980, the US share of world GDP dwindled from about half to around one quarter. But relative decline did not prompt a recalibration of burdens, not right away. Rather, the United States became in the 1980s a net importer of capital. Through the century’s end – and beyond – the tidal wash of foreign savings into its capital markets kept the US balance of payments afloat. The underlying dynamics of the Pax Americana had reversed: the United States still bore exceptional burdens, but foreign investors, increasingly, were paying the bills.

The reorganisation of the Pax Americana upended the superpower’s relationship to globalisation. Some Americans benefitted from the loosening of constraints on trade and investment; others did not. Inequalities widened. The manufacturing towns of Indiana, Michigan, and Ohio that had won the Second World War and built the Pax Americana now ceded production – and jobs – to East Asia, whose breakneck industrialisation after 1980 transformed the world economy.

New York City benefitted, in aggregate terms. The city had struggled in the 1960s and 1970s, losing population to neighbouring suburbs. New York rebounded in the 1980s and 1990s, buoyed by financial globalisation. But the influx of money aggrieved some New Yorkers, including middling property developers who struggled to compete with Japanese bids for marquee real estate.

Aggrieved, Donald Trump in 1987 took out paid advertisements denouncing Cold War allies as ingrates and unfair competitors – unworthy beneficiaries of military protection, for whom US taxpayers bore the costs. The time had come, Trump argued, to put American firms and workers first.

Trump’s message was at odds with the Cold War triumphalism that gushed in the 1990s. For the moment, a bipartisan consensus around American internationalism still endured. Republicans intended to widen the margins of American ‘hyperpower’; Democrats aimed to promote liberal values worldwide.

But American internationalism soon encountered headwinds. The wars that followed 9/11 exposed the failures of national security institutions, from the intelligence community to the National Security Council. Even worse, the 2008 financial crisis exposed Americans’ vulnerability to the volatility of advanced globalisation: the bursting of a price bubble in the housing sector exposed Americans to a credit crunch and prolonged recession reminiscent of the 1930s.

These developments stirred a subterranean reaction. On the surface of American politics, a bipartisan consensus still espoused an internationalism that conflated the nation’s interests with the interests of the wider world and the preservation of a liberal world order. But Americans were grasping for alternatives. The result was the election of Donald Trump.

Trump struggled in his first term to dominate national security institutions that retained muscle memories of the Cold War. He did not achieve much of what he sought, and the implosion of his approval ratings during the Covid-19 pandemic allowed Joe Biden to recapture the White House, promising to restore the old internationalism. Biden faltered. His attempt to recast foreign policy around a new dichotomy between democracies and autocracies did not rally a national consensus as Cold War internationalism had done. Meanwhile, Trump lurked in the wings.

The presidential election of 2024 delivered a victory far more emphatic than that of 2016. Experienced and prepared, Trump dominated his administration from the outset. Remaking the terms of international order ranked among his highest priorities. To this end, he slapped punitive duties on trading partners, irrespective of political relationships. Even more striking were the shifts in defence policy. In February 2025, Trump’s defense secretary declared that the United States was no longer ‘the primary guarantor of security in Europe’. The era of Pax Americana was over.

To witness Trump, Foreign Affairs observed in 2016, is to be ‘present at the destruction’. The phrase inverted the title of Dean Acheson’s memoir, making an historical argument: Donald Trump was a wrecking ball aimed at the world order that America had supposedly constructed through enlightened, architectural statesmanship at the end of the Second World War.

The problem with this argument is that it exalts a mythic history. The postwar order was not built according to a coherent design. Rather, it evolved through fits and starts, improvisations, and reversals. Like our metaphorical cathedral, key elements of the postwar order underwent convulsive shifts, even in their doctrinal foundations. Founded for Keynesian purposes, the IMF became an advocate of neoliberal globalisation, of the sort that Milton Friedman espoused. Too often rendered in two dimensions, the history of postwar institutions was, in fact, jagged.

What lessons might an unflattened history of the postwar order teach today? And what might these lessons suggest for allies of the United States that must adapt to an American foreign policy less predictable than any encountered in the postwar era? I offer five.

Don’t dismiss Donald Trump as a freak of history. Trump is a figure so singular that he tempts us to see him as an aberration, without whom American foreign policy would have continued along its familiar path. This view is mistaken. Trump was not merely a driver of disruption; his rise reflected deep structural cleavages in American life – cleavages that globalisation had hastened and exacerbated over at least half a century. Trump’s genius, such as it is, was to grasp with unusual clarity the improbability that international order could forever hinge upon America’s willingness to shoulder singular burdens, and to communicate this insight effectively to voters.

Don’t mourn the crumbling of a comprehensive global architecture. The postwar order was never a coherent architectural structure; it followed no blueprint, and its components often stood independently. In the Cold War era, the international order under US protection resembled a cathedral with two wings: one East Asian, the other European. Trying to preserve the entire edifice exceeds the capacities of any single power, even the United States under different leadership. America today no longer enjoys the geopolitical advantages it held in the 1950s. A wiser approach for British policy may be to focus on preserving the European wing.

Don’t await an imminent restoration of Harry Truman’s America. The United States, in truth, has for decades urged its NATO allies to assume greater responsibility for their own defence. Eisenhower first sought to recalibrate burdens away from the United States, and every successor echoed this theme in some form. In this context, Trump accelerated but did not fundamentally alter the longstanding American retreat from Europe. This pattern, intensified under Trump, poses special challenges for British policy, which lashed itself tightly to Washington in the aftermath of the Suez Crisis and has seldom reconsidered this choice.

Don’t forget missed opportunities to improvise alternatives to Pax Americana. Recall Charles de Gaulle’s proposal after the Suez Crisis for Washington, London, and Paris to recast the Western alliance as a trilateral directorate, with European powers sharing leadership. From the vantage of 2025, de Gaulle’s 1958 proposal appears not so much nostalgia for French grandeur but rather an astute assessment of the unsustainability of a military alliance centred on the singular capabilities of a reluctant, distant superpower. Despite its erratic tendencies, French postwar policy displayed a scepticism that British policy often lacked. Reflecting on missed opportunities might underscore the strategic value of Anglo-French collaboration today and in the future.

Don’t seek architectural solutions for a crumbling cathedral. Recall that the postwar order emerged through particular policies addressing particular problems – not grand designs. Pax Americana’s founding acts were the Truman Doctrine and the Marshall Plan. Neither was a permanent solution, and both seeded future challenges: the Truman Doctrine prefigured Vietnam; the Marshall Plan led indirectly to balance-of-payments crises that roiled the dollar in the early 1970s. Yet subsequent leaders solved these emerging issues in due course. During the 1970s, liberalising capital flows and recycling petrodollars provided temporary fixes for imbalances.

Put simply: diplomacy’s greatest achievement is improvising practical solutions to real problems. Fixating on architectural visions, by contrast, risks paralysis. To be effective, diplomats today might emulate their predecessors from the late 1940s: with world order in crisis, they should put away their easels and blueprints, pick up their files, and start chiselling.

An earlier version of this paper was commissioned by the Centre for Grand Strategy at King’s College London, as part of their ongoing applied history work for the UK Cabinet Office.