Are we truly witnessing the destruction of the rules-based international order that was created, however imperfectly, in the aftermath of the unparalleled world wars and crises of the 20th century? Are we truly on the cusp of a new ‘age of strongmen’ dominated by authoritarian leaders like Trump, Putin and Xi Jinping, in which the strong impose and the bullies get what they can – and the weak suffer and concede what they must?

Unquestionably, we live in a ‘time of turning’, in which Putin relentlessly expands his war of aggression against Ukraine, Xi Jinping’s China advances its own revisionist agenda vis-à-vis Taiwan, and upheaval in the Middle East seems unstoppable. We are also witnessing how relentlessly Trump seeks to dismantle not only liberal-constitutional government in the United States but also the postwar order whose creation America shaped so decisively. Some observers have claimed that this catapults us back to the ‘might over right’ politics of 19th-century imperialism, which set the stage for a ‘short’ 20th century of extremes. But is the world really bound for endemic disorder in which ruthless ‘mafia powers’ compete for primacy?

It is premature to draw such conclusions. Instead, the focus should be on two different and indeed crucial questions: how can we not only salvage but actually renew the core of the rule-based modern order that was first conceived after 1918 and then created after 1945? What deeper lessons can we draw from the decisive transformation and learning processes that made such advances possible?

To answer these questions, it is essential to map out a wider historical context. To be illuminated is the transformative long 20th century. In my interpretation, this century dawned roughly around 1860, when the globalisation of capitalist and imperialist competition remade the world. It ended around 2022, when its hard-won and unfinished order came to be unmade – or was renewed for the 21st century.

Indeed, not only the unprecedented catastrophes of the long 20th century but also its remarkable achievements hold salient lessons for today. Following a formative period of global conflagration, new peacemaking attempts, escalating crises and an even more horrendous second global war, the century gave rise to the closest humanity has ever come to a functioning and legitimate international system – even if this system never evolved into a truly global order. For these advances it was critical to commit the exceptionalist American republic to a responsible hegemonic role in the world. They were always made in systemic competition with rivalling visions and forces – in struggles against traditionalist authoritarianism and communism, then against fascism, National Socialism and Japanese hyper-imperialism, and eventually against Stalinism and Maoism.

The novel peace system that emerged after the Second World War should be characterised fundamentally as a rules-based order. At the core, it was built on a new Atlantic concert of democratic states, which also extended to East Asia. Led by a now benevolent (overall) American superpower, the members of this concert were bound together not just by alliances and institutions, but also by common understandings about core rules of conduct, democratic government, collective security, and the value of an essentially social-liberal market economy that regulated capitalism. Leading decision-makers managed largely to meet one critical challenge, namely to legitimise such demanding rules and understandings in the increasingly complex force-fields of modern democracy.

Owing to the Cold War’s systemic divisions and imperialism’s burdensome legacy, this concert system remained essentially Euro-Atlantic. When, after the caesura of 1989, a new opportunity finally arose, the decisive Western actors did not do enough to turn it into a more inclusive rules-based world order. This eventually made it especially vulnerable to populist and authoritarian attacks. Indeed, the current rupture raises the spectre of its fundamental disintegration. Yet it might also become an existential ‘time of turning’, in which deeper learning processes become possible and the unfinished order of the long 20th century may yet be reinvigorated. But whoever seeks to do so must realise that the ‘old order’ cannot, and should not, be restored; it must be renewed and globalised to be sustainable in the 21st century.

To highlight cardinal lessons, and paths from crisis to renewed order, I will focus on three transformative core periods that reshaped the world between the era of high imperialism and the long aftermath of the Cold War. The first began on the eve of the Great War, culminated in the first bids for a modern peace – in 1919 and the formative 1920s – and ended with the Great Depression. The second began in the abysmal 1930s and culminated in the more far-reaching bids to create a new order after 1945. The third began with the transformative revolutions of 1989 and culminated in aspirations to construct a rules-based post-Cold War order, which then unravelled.

The crucial transformations that still shape our world do not stem from an overpowering rivalry between US-led liberal capitalism and Soviet-led communism in the ‘short’ 20th century. Rather, their origins lay at the dawn of the long 20th century. For then, in the 1860s, a novel world-historical constellation emerged. What eventually swept away the Vienna system of 1815 and the Eurocentric ‘world order’ of the 19th century was not only modern capitalism but also the globalisation of imperialist power politics. An ever more limitless struggle for ‘the survival of the fittest world power’ escalated. The still dominating club of European empires were joined by two new aspirants, Japan and the United States, which in the era of William McKinley and ,Theodore Roosevelt acted as a self-styled policeman in the western hemisphere and a rapacious informal empire in East Asia. Espousing a crude civilisational Darwinism, these power-states forced all those they classified as ‘less civilised or developed’ – including the ailing Chinese Empire – under exploitative forms of domination, which have far-reaching consequences to this day.

In 1914, Europe’s decision-makers did not sleepwalk into the Great War. Rather, the conflict broke out because they had failed to develop further a basically sound international system to meet new global challenges. This is the critical lesson that can be drawn from what happened to the Concert of Europe, which had long committed the main European powers to effective rules of peace preservation and conflict resolution. At the height of the July Crisis, it became obvious that this concert had become practically defunct – and the new US President Woodrow Wilson had neither the power nor the authority to step in decisively.

When the First World War ended, it had raised enormous expectations for a ‘peace to end all wars’. Yet for those who then, in Paris, dominated the most complex peace-making process in history – the democratic leaders of the victors, Wilson, Georges Clemenceau and David Lloyd George – it was simply impossible to fulfil these expectations. No Wilsonian ‘new world order’, anchored in the novel League of Nations, could be founded.

Yet nor was it possible to impose a peace-enforcing balance of power on the vanquished. A more durable and legitimate peace could only be made through an inclusive negotiating process that yielded mutually acceptable ground-rules for an integrative postwar order. Systemically, the crucial requirement was the creation of new concert of democratic states that comprised not only the Western victors, but also vanquished, the fledgling Weimar Republic, and the new East European states. Yet the peace of Paris was made on much frailer foundations and remained essentially incomplete. Rather than lay the groundwork for a viable global order, the main peacemakers created a new Atlantic order of the victors, which not only the losers of the war deemed illegitimate. It excluded both Weimar Germany and Bolshevik Russia. And it rebuffed anticolonial nationalists’ demands for ‘self-determination’, forcing them to remain under imperialist domination within the League’s neo-imperialist mandate-system.

Thus, the victors’ peace of 1919 was only a fraught beginning of efforts to construct a durable order for the long 20th century. Meanwhile, Wilson’s subsequent defeat in the ‘Senate fight’ over the Treaty of Versailles underscored how challenging it would be to engage the untested American hegemon in such efforts.

It is important to stress, however, that neither the flawed settlement of Paris nor America’s withdrawal led inevitably to the rise of Hitler and another world war. In fact, the post-First World War era became not a ‘time of illusions’, but rather a remarkable period of progress and learning in world politics. In the critical 1920s, not only the European protagonists of democratic postwar politics, but also the eminent American Secretary of State Charles Hughes found ways to overcome the constraints imposed by Versailles, selective US isolationism and unilateral Congressional tariff policies that culminated in the disastrous Smoot-Hawley Act of 1930. Crucially, they drew tangible consequences from the shortcomings of 1919.

Thus, the contours of a new international order emerged. The seminal agreements of the 1922 Washington Conference established the first global arms-control regime – in the vital naval sphere – and prepared the ground for a renewal of Chinese sovereignty and a more tenable East Asian status quo. Even more significantly, with vital American support the architects of the Locarno security pact of 1925 – Briand, Stresemann and Austen Chamberlain – managed to negotiate the most consequential ‘real’ peace settlement after the Great War. Above all, Locarno finally gave rise to a reconfigured Euro-Atlantic concert that not only included Britain, France and Weimar Germany, but also, as tacit underwriter, the United States.

Ultimately, however, these remarkable advances could not be made sufficiently robust to cope with the shockwaves of the world economic crisis unleashed by the Great Depression. This was mainly due to the Hoover administration’s refusal to orchestrate coordinated international countermeasures in the wake of the Wall Street crash of 1929. Hoover’s successor, Franklin Delano Roosevelt, then saw no other option but to launch his transformative New Deal, which transformed the American state and society, as a national reform programme, turning America’s back on the world. The collapse of the fledgling order of the 1920s thus highlights the dire consequences of not making a new international architecture resilient, and of foregoing concerted efforts to tackle fundamental crises. This is what finally created the power vacuum that enabled Mussolini, Japan’s new hyper-militarist leaders and, most consequentially, Hitler to pursue their barbaric acts. Yet Roosevelt’s exceptional leadership ensured that liberal democracy remained a viable form of government and that the American republic could eventually play a decisive role in defeating the Axis powers.

The Second World War led to the most horrific violence, destruction and moral degradations in human history, which reached their nadir in the Holocaust. It also gave rise to something else: the second and hitherto most impactful process of learning and reordering in the long 20th century. Deeper changes in individual ideas and collective mentalities and a reinforced willingness to learn from the calamities that had arisen since 1914 now animated more far-reaching aspirations to create a veritable new world order. These aspirations informed a fundamental political struggle that had two distinct phases.

First came the remarkable bid – pursued under Roosevelt and Churchill, in tense collaboration with Stalin – to construct a postwar order for ‘One World’. This was to be achieved through a United Nations system that remedied the limitations of the League, not least by giving the principal victors the authority to ‘police’ the world as permanent members of the new UN Security Council. It was to be buttressed through the novel institutions of Bretton Woods, the World Bank and the International Monetary Fund. Yet these global aspirations were based on an unrealistic premise – the assumption that a basic hegemonic cooperation between the Western allies and the Soviet Union could be maintained.

More significant was the second phase of systemic transformation, which began in 1947. What now unfolded was undoubtedly influenced by the escalating confrontation between the American and Soviet superpowers – and eventually Mao’s China. It was influenced by the advent of nuclear weapons and the deterrent ‘logic’ of mutually assured destruction. On a deeper level, however, a veritable political revolution occurred, chiefly in the transatlantic sphere, which was the outgrowth of longer-term learning processes. Drawing fundamental lessons from the limits of Versailles and the cataclysms of the 1930s and 1940s, key architects of the new order such as George Kennan and Jean Monnet, Ernest Bevin and Robert Schuman, Konrad Adenauer and Dean Acheson, as well as countless other formal and informal actors, did not envisage a Pax Americana dominated by a new US ‘super-empire’. Rather, they set out to construct a qualitatively new Pax Atlantica, premised on the realisation that this time it was vital to create a more resilient concert of liberal-democratic states and societies.

This novel system would then be based not only on far-reaching inter-state agreements, notably the European Recovery Program and the North Atlantic Alliance. It would also be founded on a newly comprehensive cooperation between a constructive American hegemon and a war-ravaged but revitalised Western Europe. This would create essential preconditions for West European steps towards supranational integration, offering the German Federal Republic a vital ‘second chance’ to become part of a renewed Atlantic community.

All of this went far beyond the goal to counter and contain Stalin’s brutal Pax Sovietica. It extended social-liberal modernisation, democratisation, human rights, and welfare-state-building to unprecedented levels. It was advanced not only by governments, but also by a wide array of transnationally cooperating activists and associations such as the Atlantic Council. Less far-reaching advances of this kind were eventually made in the US-led alliance system in East Asia. For all its shortcomings, the making of the Pax Atlantica stands out, therefore, as a rare example of what it means to advance effective common rules and concerted approaches to meet fundamental challenges. Its protagonists not only managed to create viable international mechanisms and institutions. They also built up a political culture informed by mutually accepted practices and norms. All of this must be considered in order to understand why the novel Atlantic order lasted so long and gained such remarkable legitimacy. Sustaining it remained an ongoing struggle in ever more demanding conditions on both sides of the Atlantic. Yet what was accomplished here still holds highly pertinent lessons for the 21st century.

Potentially, the Atlantic peace system could indeed become the nucleus of a rules-based global order. but during the Cold War its advances remained essentially confined to the Euro-Atlantic sphere. Nonetheless, it had global repercussions. It became entangled with the violent struggles of decolonisation and in a global Cold War that was fought – in Latin America, Africa, Vietnam and elsewhere – in ways that blatantly contradicted the standards and values the proponents of the Atlantic community had proclaimed. Thus, a widening chasm opened up between the norms and rules that prevailed inside and outside the realm of the Pax Atlantica. Would it ever be possible to overcome this chasm and progress towards what the world that the long 20th century so desperately needed: a universally valid and effective rules-based system, a Pax Mundi? This question would pose itself with renewed urgency after the watershed of 1989.

In the aftermath of the Cold War, a profound problem of learning arose, and not only in the West. The critical challenge became to eschew the misleading lessons of triumphalism – to avoid the complacent conclusion that the end of history had been reached and one now had to simply refashion the formerly communist and non-aligned parts of the world according to Western modes and orders. Instead, even if one could build on valuable Euro-Atlantic premises, it was imperative to acknowledge that one faced a far more complex challenge – that of finally creating a genuinely global system of order. A system was needed that provided rules and mechanisms, not only to deal with the crises and demanding transition processes after 1989, but also to regulate the dynamic globalisation processes that now accelerated.

Yet precisely because the Cold War had ended so differently from the two world wars, the prevalent assumptions that informed both Western and non-Western postwar approaches made deeper learning much harder, which in turn blocked more substantial advances. What came to dominate were self-serving ideas not only about how inevitable the globalisation of Western rules would be, but also about how much they would benefit everyone, irrespective of where one stood on the still very asymmetrical global playing-field.

During the transient phase of ‘US unipolarity’ in the 1990s, there were far too few substantive debates about alternatives to unlimited globalisation and the harder tasks of global reordering. While requiring all others to adapt to them, political leaders and wider publics in the West missed the opportunity to learn not only from history but also from the experiences of East European revolutionaries and from those who had struggled in the ‘Third World’.

There was never any real prospect for a lasting ‘unipolar order’ under American auspices, but the US superpower and its allies now had new responsibilities. One was to broaden the global acceptance of democratic and social-liberal standards. Another was to accommodate a crisis-ridden post-Soviet Russia within a rules-based order. On different premises, this was also the key challenge vis-à-vis a newly assertive Chinese regime following the Tiananmen Square massacre of 1989. There was no new ‘clash of civilisations’. Rather, deeper political fault-lines of the long 20th century, which had been submerged during the Cold War, now reappeared. Neoliberal globalisation sharpened rather than lessened political and ideological polarisation.

It would be misleading, however, to conclude that no progress was made at all after 1989. Especially significant as the process of German reunification, as well as the overly aspirational, eastward expansion of an also deepening European Union. No less important were efforts to build on the seminal Helsinki process of the 1970s and create a broader Euro-Atlantic peace architecture – first by the strengthening Conference on Security and Cooperation in Europe through the 1990 Paris Charter, then by creating the Organization for Security and Co-operation in  Europe (OSCE) in 1994.

One should also highlight the successful bid to reorient the North Atlantic alliance and integrate East European states keen to join it. One should also recognise successive attempts to place relations with Russia on new foundations, which led to the NATO-Russia Founding Act of 1997 and further agreements, which Putin’s imperialist aspirations then violently undermined.

With a view to China, many Western protagonists hoped that drawing the new economic superpower into hyper-capitalist globalisation processes would also promote liberal-democratic reforms. Yet Xi Jinping’s rise to power dashed such hopes, firmly advancing his counter-vision of combining capitalist pursuits with authoritarian ‘communist’ rule. This created a vital question that must still be confronted – how to deal with a China that is selectively cooperative but also prepared to contest core international rules, particularly over Taiwan, threatening more than just Asian-Pacific stability.

The West’s ability to master these challenges was gravely affected by the neo-imperial American response to the terrorist attacks of 9/11, especially the 2003 invasion of Iraq. This response not only damaged the United States’ global authority; it corroded the legitimacy of western conceptions of a universal rules-based order and human rights. Despite notable advances, the post-Cold War era must thus be viewed as one of the most consequential periods of unresolved systemic problems and constrained learning in the long 20th century.

Hence, two deeply disconcerting trends have arisen, which mark the end of this century and the true beginning of the 21st: the hollowing-out of the underlying rules and norms advanced after the Second World War, and the descent into a new and profound systemic rivalry. At its core lies the competition between a community of still social-liberal-democratic states – which, in the Trump era, is also challenged by authoritarian-populist forces from within and has lost (for now) its longtime US hegemon – and the unabashedly authoritarian counter-models represented by China, Russia, Hungary under Órban, and Turkey under Erdogan. Both of these trends have deeply unsettled global order, and both have made it even tougher to address the more fundamental task we face: to forge, at last, a sustainable overall framework for relations between the two equally diverse spheres of the ‘Global North’ and ‘Global South’, or rather ‘Global Majority’, at a time when overarching global challenges desperately demand common responses.

Arguably, it is more imperative than ever not only to hammer out genuinely universal ground rules of world politics, but also to practise and enforce them. It is more vital than ever to prove that such rules and practices provide the most effective means to master the world’s cardinal problems – from its perennial security challenges to the critical tasks of regulating globalisation, ensuring more equitable development and dealing with climate change and migration.

This is why, in today’s watershed crisis, the leaders of Europe, Canada and those who struggle for democratic and social-liberal values in other parts of the world, including the United States, have a vital responsibility. Learning from the long 20th century’s transformations commands us not to assume that a demise of global order is unavoidable. It may seem paradoxical, but the very magnitude of the current evisceration of order and rules through authoritarian-populist ‘strongmen’ – by Trump, Putin, Xi Jinping and those who emulate them – carries a seed of hope. It may finally create the conditions and pressure required for veritable systemic renewal, propelling learning processes that otherwise would be unthinkable. The stakes could not be higher.

What, then, can and should be done? The first vital task is to build on the example set after 1945 and revitalise a cooperative and indeed exemplary concert of democratic states. Europe’s democracies should not give up on NATO and the transatlantic partnership, but they must do far more to create a more effective European system, and pillar, within it. The wider aim of their efforts should be to contribute to an ultimately more sustainable Euro-Atlantic peace system – and to build bridges towards Atlanticist and internationalist Americans who support such efforts beyond Trump’s presidency. The recent Defence and Security Pact agreed between the EU and Britain is a step in the right direction. In the short term, it will be essential for the reinvigorated concert to prioritise aiding Ukraine to prevail against Putin’s aggression and containing Russia by all available means. In collaboration with partners like Japan, similar policies should be pursued to pre-empt Chinese attempts to annex Taiwan or subvert international ground rules in and beyond East Asia. The longer-term aspiration should be to strengthen both regional and global collective security, the resilience of pluralistic democracies, and a more balanced social market economy that reins in hyper-capitalist disorder and inequities. The guiding maxim should be to renew the legitimacy and attractiveness of a rules-based order, and democratic concertation, from a regained position of strength.

Substantial progress in this direction is inconceivable without the political will of leading decision-makers as well as wider societies – not only in Europe and North America – to embark on harder learning processes. They must confront entrenched patterns of hierarchical thinking, complacency, self-serving ideologies and illusions. Crucially, however, they must draw tangible consequences from the achievements – and the limitations – of those who sought to rebuild international order in the wake of the world wars. And they must concentrate on completing what was left unfinished after 1989 and make every effort to create a truly integrative and global concert for the 21st century. This concert should be open to all states and societies willing to commit themselves to its core rules and understandings; and it should encourage all not only to make such commitments but also to cooperate in the renewal of world peace and world order.