At the close of the momentous conference of Locarno, the British foreign secretary Austen Chamberlain declared, on 23 October 1925, that the security pact the major European powers had just concluded, and its guiding spirit, marked ‘the real dividing line between the years of war and the years of peace’ in Europe after the cataclysm of the Great War. Later, however, the Locarno Pact came to be viewed as the epitome of a ‘decade of illusions’ between Versailles and a purportedly inevitable Second World War. And it was even placed in the pre-history of the fateful ‘appeasement’ of Hitler Germany in the 1930s. But this is profoundly misleading.

A reappraisal from the distance of 100 years shows that the Locarno process and its politics still offer valuable lessons for the 21st century – including lessons about what it takes to forge paths from war to more sustainable peace and order, in Europe and beyond. And it will illuminate that decisive changes can be propelled by a fundamental reorientation of ideas about and outlooks on international politics. Those who became the chief architects of Locarno – Chamberlain and his counterparts Gustav Stresemann and Aristide Briand – embarked on significant learning processes. They confronted a world transformed by the First World War, in which the old European order had been destroyed, the new American world-power pursued selective isolationism, and Soviet Russia posed novel challenges. They drew tangible consequences not only from the war, but also from the deficiencies of the imposed peace of 1919. And they realised that on a recast international playing field, dominated by newly broadened or just-established democracies, they had to forge agreements that could be legitimised in very unsettled national force-fields. What they accomplished in 1925 was thus all the more remarkable because of the scale and number of challenges they faced.

The Locarno accords were in fact the first ‘real’ peace settlement after the Great War – negotiated between the victors and the vanquished. They laid the groundwork not just for a new European security architecture but also for a novel European concert of democratic states. In a wider context, they created the best possible prospects for preventing what all the key actors feared: another world war. And they, in fact, prefigured the more far-reaching European and Euro-Atlantic advances that were then made, and were only possible, after 1945.

The Great War had left daunting challenges in its wake. Costing the lives of more than 11 million, it had not only swept away the pre-1914 system of war-prone alliances between competing empires. It had also created unprecedentedly deep political and ideological divisions between the eventual victors and the defeated powers. Behind this lay the deeper structural problems that had accrued during decades of globalising imperialist rivalry and power politics since the 1860s, the dawn of the long 20th century.

The peacemakers of 1919 could never fulfil elusive expectations for a ‘peace to end all wars’. No Wilsonian new world order, safeguarded by the novel League of Nations, could be founded. Yet nor was it possible to construct a peace-enforcing balance-of-power system that contained Germany. Ultimately, the hybrid peace of Paris came to rest on much frailer foundations – a strained combination of collective security, Anglo-American pledges, and territorial guarantees – and was then greatly weakened by the US Senate’s rejection of the Treaty of Versailles. Thus, a truncated system of the victors emerged. Imposed on the losers, together with massive yet unspecified reparations, it clearly lacked overall legitimacy and excluded Europe’s two biggest powers: an unstable republican Germany, beset by a ‘revision  syndrome’ after an unacknowledged defeat; and – eventually – a Soviet Union seeking to spread ‘world revolution’ to the west. At the same time, Eastern Europe had been left structurally unstable, with the newly constituted Polish and Czechoslovakian states comprising sizeable German-speaking minorities and the contested Polish-German border becoming a fault-line of postwar politics.

Europe soon descended into a profound postwar crisis. At its root lay the unsettled German question and the unresolved Franco-German antagonism. It soon became clear that neither France’s insecurity nor European instability could be remedied by enforcing or even exceeding the terms of 1919. This was revealed starkly during the pivotal Ruhr Crisis. Having failed to get British backing for his reparation and security demands, the combative premier Raymond Poincaré in January 1923 ordered French troops to occupy Germany’s industrial heartland to enforce German ‘fulfilment’ and France’s continental predominance. Yet his unilateral actions provoked not only German ‘passive resistance’ but also a caesura in postwar politics. What ended the Ruhr conflict, after a decisive US intervention, were the watershed accords reached at the London Conference of 1924. They brought the first mutually acceptable reparations settlement, based on the Dawes Plan – more importantly, they initiated an American ‘economic peace’ underpinned by US loans to Weimar Germany.

The sea-change of 1924 also created a new urgency to tackle the unsolved security question – to construct a framework for Europe’s incipient stabilisation that made Weimar Germany’s consolidation compatible with the security needs of its neighbours. Neither a new Anglo-French alliance nor a fortified collective-security system of the League would furnish such a framework. Poincaré’s socialist successor Édouard Herriot had proposed to establish – through the ‘Geneva Protocol’ – a stronger regime of obligatory arbitration and automatic sanctions to forestall renewed German aggression. In September 1924, Britain’s first Labour premier, Ramsay MacDonald, called for a more integrative ‘system of universal reconciliation and arbitration’. But the new Conservative British government then vetoed the Geneva Protocol. By early 1925, a fresh approach had thus become imperative. This set the stage for the Locarno process.

What prompted this transformative process was the farsighted security initiative launched by Gustav Stresemann in January 1925. Once an advocate of far-reaching imperial-annexationist schemes during the war, the man who became the Weimar’s Republic’s pre-eminent statesman went on to draw fundamental lessons from this catastrophe and its fallout. The result was an elaborate strategy of security- and concert-building that he developed with his trusted adviser, Under-Secretary Carl von Schubert. Its core premise was that Germany had to recognise the basic ‘realities’ of Versailles and offer cooperation and reassurance to the key western powers – and its eastern neighbours – to prepare the ground for peaceful change. Stresemann’s underlying aim was to propel Germany’s integration into a reformed Euro-Atlantic order as a republican great power with ‘equal rights’. Schubert even explicitly prioritised Germany’s return to ‘the concert of powers as an equal partner’. This new republican foreign policy was decidedly western-orientated, clearly departing from earlier ‘eastern orientations’. Yet Stresemann intended to pursue it without antagonising Soviet Russia.

With these wider aims in mind, the German foreign minister proposed an agreement with France and the other states bordering the Rhine, in which all signatories recognised the territorial status quo set in 1919. Alongside Italy, Britain was to be the key guarantor. Further, Germany offered arbitration treaties not only with France and Belgium but also with Poland and Czechoslovakia, renouncing the use of force but retaining the option of peacefully altering the eastern status quo in the future. This remained a long-term aim but was also a domestic necessity. Essentially, recognising the Polish-German border would have derailed Stresemann’s entire initiative because of the widespread opposition it would have aroused, far beyond the German nationalists in Hans Luther’s coalition government.

Ensuring support for his new course in Weimar’s polarised political spectrum would remain a critical challenge for him. Strategically, his security policy was integral to the modern, economically-orientated ‘Weltpolitik’ he envisaged, and he counted on America’s interest in Europe’s political stabilisation. But he reckoned that the isolationist Coolidge administration would not underwrite the Rhine pact. He therefore sought to enlist Britain as an essential mediator.

Indeed, Stresemann’s overture would have been frustrated if Britain’s new Conservative foreign secretary Austen Chamberlain had not assumed the role of an ‘honest broker’ who sought to reassure France and integrate Weimar Germany into a renewed European concert. By the spring of 1925, Chamberlain had undergone a learning process of his own. Initially, he recommended a more traditional approach: a bilateral Anglo-French alliance to counter German revisionism. But he then reoriented British policy, pursuing a new forward engagement, whose underlying aim was to ensure that, after the traumatically costly Great War, Britain would never have to go to war in Europe again. Aided by the British ambassador in Berlin, Lord D’Abernon, he came to regard the proposed pact as the ideal instrument to this end.

Chamberlain feared that if the victors failed to accommodate the ‘colossus’ at the heart of Europe, Germany would be driven into a dangerous alliance with Soviet Russia. Yet his engagement was also influenced by Britain’s global interests – the need to consolidate a far-flung imperial system that had been further expanded in 1919 and was challenged by Indian and Egyptian nationalists and a widening Chinese civil war. The global rationale for Chamberlain’s Locarno policy was that Britain’s imperial system could only be maintained if a new equilibrium could be created that prevented any one power from dominating Eurasia and threatening it anew.

Chamberlain was aware of the United States’ new power as war-debt creditor and key player behind the Dawes regime. But his experience since Wilson’s fiasco had led him to conclude that only Britain had it ‘in her power’ to ‘bring peace to Europe’. It had to ‘remove or allay French fears’ and ‘bring Germany back into the concert of Europe’, thereby also strengthening its fledgling democracy. More fundamentally, Chamberlain sought to adapt to the 20th century what Castlereagh had achieved at and after the Congress of Vienna when creating the original European concert and then incorporating post-Napoleonic France. Yet he also sought to limit Britain’s guarantees to what he could present domestically as the strategically vital region, Western Europe, while avoiding undesirable commitments in the east. Chamberlain thus deemed it all the more important to bind Germany to a western system of rules and restraints. British strategists argued that this would provide ‘new security’ for Poland and Czechoslovakia, creating a ‘nucleus of certainty, of stability and of security’ that could expand eastward.

The third protagonist of Locarno, Aristide Briand, thus confronted a new Anglo-German dynamism that challenged core premises of French postwar policy. Unsurprisingly, he began by demanding stronger safeguards for France and its eastern allies against German revisionist pressure. Yet the French foreign minister soon realised that ‘a particular Anglo-French accord for the security of the Rhine’ was no longer possible. Acknowledging Chamberlain’s new priorities, he came to see the opportunity Stresemann’s initiative presented.

More fundamentally, he too had drawn lessons from the deficiencies of Versailles and the coercive postwar policies that had overburdened a profoundly exhausted French power. He, too, considered it vital to place European and Franco-German relations on a new basis – from ‘security through enforced containment’ to ‘security through restraining cooperation’. And he came to view the pact proposal as a means to this end – and as a way to obtain, finally, tangible British guarantees. Consequently, Briand became the pivotal French champion of the security pact, defending it against considerable domestic opposition, particularly from the nationalists of Poincaré’s Bloc national, who accused him of betraying France’s vital security interests.

Supported by the Quai d’Orsay’s secrétaire général Philippe Berthelot, Briand initiated a fundamental paradigm-shift to address France’s core strategic dilemma, which neither its armed preponderance nor its expanded overseas empire could lessen. That dilemma was the structural imbalance between a nation of 40 million and a menacing neighbour, outre-Rhin, of roughly 70 million and with a far superior power potential. Briand’s main rationale was to tie Weimar Germany into a reformed postwar system designed to pre-empt future German aggression. He now impressed on his critics that the ‘reconstitution of Europe’ required not an alliance ‘forged against one state’ but rather ‘a guarantee pact that proceeded from a spirit of mutual aid’.

Ultimately, he sought to enable France to control, with Britain’s help, an evolving but not radically altered status quo, while deepening political and economic co-operation with Weimar Germany. De facto, Briand subordinated France’s alliance commitments to Poland and Czechoslovakia to these new priorities. Yet he insisted on the firmest possible German assurances in the east and, eventually, a French guarantee of the arbitration treaties. More important for him, however, was to revive the battered partnership with Britain and to mend France’s strained relations with the United States. In the midst of yet another French financial crisis, he argued that the Painlevé government could no longer afford to antagonise Washington and the ‘power of the City of London and of Wall Street’.

Both Republican decision-makers in Washington and leading US financiers were in fact interested in a success of the security pact, viewing it essentially as the ‘political insurance’ of Europe’s nascent ‘economic peace’. Yet they had also drawn constraining consequences from the success of 1924. After the London conference, the designated new secretary of state, Frank Kellogg, declared that the United States would have ‘much more influence’ if ‘we maintain our freedom of action’, helping the Europeans without getting ‘tied up’ in European politics. Wrestling with complex security issues was essentially viewed as a European responsibility. The American role was to exert financial-cum-political power in the background. On these premises, the US ambassador in London, Alanson Houghton, on 4 May 1925 delivered ‘America’s Peace Ultimatum to Europe’, calling on ‘the peoples of Europe’ to negotiate a ‘permanent peace’ if they wanted to continue to benefit from American loans.

The Locarno conference, held from 5 to 16 October 1925, heeded this call. It not only inaugurated but also brought the first culmination of what hence became widely known as ‘Locarno politics’.  And it brought a decisive shift. The search for complex, tenable and legitimate compromises between the victors and vanquished now superseded the antagonistic politics of the postwar years.

Those who negotiated these advances were, chiefly, the members of the emerging Locarno triumvirate – Chamberlain, Stresemann and Briand – aided by their delegations. While Mussolini played only a peripheral part, those who represented Polish and Czechoslovak interests, the foreign ministers Aleksander Skrzyński and Edvard Beneš, were only invited to the final deliberations on the eastern arbitration treaties. They came to Locarno with understandable security concerns, demanding an ‘eastern Locarno’ with equally firm guarantees for their borders. But such demands were refuted, and they perceived themselves as ‘second-class participants’ of proceedings that also inaugurated a new mode of democratic great-power diplomacy.

Nonetheless, the agreement of 1925 should be seen as the most significant peace accord of the post-First World War era, not just for the western powers and Germany. It actually transformed the truncated Versailles system, opening up the most auspicious postwar prospects for a more durable European and Euro-Atlantic order. Concretely, with Britain and Italy acting as guarantors, the German government accepted the postwar status quo in the west. And, against vociferous nationalist opposition at home, it did conclude arbitration treaties with Poland and Czechoslovakia that were guaranteed by France and committed Germany to the renunciation of force.

In return, Chamberlain and Briand accepted that Weimar Germany would be reintegrated into the ‘comity of nations’ as a European great power with ‘equal political rights’. Through the prism of what occurred in the 1930s, it has often been claimed that the now often-invoked ‘spirit of Locarno’ was one of illusory ‘appeasement’ that ultimately allowed Hitler to undermine peace. But the Locarno pact by no means marked a false dawn. It was neither inherently flawed nor bound to remain ephemeral. By founding a novel concert of democratic states that, at its core, comprised Britain, France and Germany, it established the crucial European mechanism that was needed to consolidate the fledgling new Atlantic order in which the United States played a pivotal but still informal role. The Locarno concert was only a nucleus. But it indeed bolstered the Weimar Republic’s inclusion into this new order – as a power that adopted western norms of international politics.

Significantly, the Locarno treaties were interlocked with the League’s Covenant and principles of collective security. And it was not just symbolically significant that Germany would soon be admitted to the nascent international organisation, as a permanent member of its council, which was finally accomplished in September 1926. The Locarno accords thus strengthened the League, for they turned it from an institution of the victors into a more integrative organisation that could now finally act as an essential international ‘clearing house’. Crucially, while both the United States and the Soviet Union still shunned Geneva, the League became the institutional platform for the Locarno concert and its interactions with smaller states.

In a wider perspective, the Locarno process had the potential to create nothing less than a modern system of order – a system predicated on the idea that mutual security agreements and concerted modes of politics and peaceful conflict resolution could yield overall gains in security and development prospects. If sustained, this process could have furthered the emergence of an effective security community and a new political equilibrium in the newly critical transatlantic sphere. This is what ‘the spirit of Locarno’ truly meant. And it was not limited to Western Europe. Unquestionably, Locarno created borders of different validity in Europe. Arguably, however, it also provided new safeguards for Poland and Czechoslovakia and new restraints on Germany’s revisionist tendencies. It relegated the explosive eastern border and minority issues to a more distant future when it might be possible to address them in a less hostile climate. And, crucially, by anchoring Weimar Germany to a western-orientated system it drew it away from Soviet temptations.

Yet the Locarno treaty also recognised Germany’s special situation. It specified that it had to enforce possible sanctions against Soviet Russia – under the League Covenant’s Article 16 – only insofar as this was ‘commensurable with her military situation’ as a substantially disarmed power and her ‘geographic (middle-)position’ in Europe. As a complement to the security pact, Stresemann then, in April 1926, concluded a neutrality treaty with Moscow that was compatible with Germany’s Locarno commitments; it came at a time when Stalin had begun his brutal reign but still contemplated a modus vivendi with the western states. Thus, within the realm of what was possible after 1918, a first groundwork for the stabilisation of Western and Eastern Europe had been laid. 

What had been accomplished at Locarno thus indeed marked a caesura between war and peace in the aftermath of the Great War. And it made possible a remarkable period of Euro-Atlantic pacification in the later 1920s, the era of Locarno. The ground-rules and playing-field of international, transnational and domestic politics palpably changed, and essential conditions were created for deeper peace-building, not least through transnational organisations like Coudenhove-Kalergi’s Pan-European Union and the Association for European Reconciliation. In the United States, internationalists like James Shotwell sought to build on Locarno to galvanise a global war-renunciation movement.

The Locarno accords could not yet ‘solve’ Europe’s postwar problems or create a stable status quo. Rather, they constituted, as Chamberlain put it, ‘the beginning, and not the end, of the noble work of appeasement in Europe’, and its stability remained fragile. Consequently, the advances of 1925 had to be carried further and gain deeper legitimacy. One vital task was to reconcile the different expectations Locarno had generated – and to prove to the different domestic audiences that Locarno politics could yield mutually beneficial consequences. Undoubtedly, dominant French expectations – that the agreements would consolidate the postwar order and slow down the pace of change – collided with prevalent German expectations that concentrated on swift ‘consequences’, notably a termination of the Rhineland occupation. Yet such challenges are the rule rather than an exception in modern international politics. What matters is that mechanisms and ground-rules exist, as well as political will, and room to manoeuvre, to tackle them effectively. And this is what the new European concert essentially provided. In many ways, the Locarno process thus anticipated future peace and reconciliation processes between democratic – and non-democratic – actors in the 20th century, both in and beyond Europe. And Locarno’s ground-rules of ‘co-operation’ and ‘reciprocity’ were bearing fruit. Most significantly, all sides made it a priority to cultivate the Locarno system.

But because the most critical issues – security, the Rhineland, reparations, and war-debts – were so inextricably connected, substantial progress could only be made through further complex political-cum-financial bargains. What the Locarno protagonists eventually aspired to was indeed a kind of ‘final postwar settlement’ that, as they knew, was inconceivable without constructive American engagement. It thus became imperative to widen the new European system into an effective transatlantic concert. However, in view of America’s persistent political aloofness this remained an up-hill struggle, which became obvious when the Kellogg-Briand Pact for ‘the renunciation of war as an instrument of national policy’ was negotiated in 1928. Kellogg converted Briand’s originally bilateral design into a universal pact whose provisions for arbitration and conflict resolution in principle complemented Locarno. But without binding commitments or sanctions against those who violated it, the Kellogg-Briand Pact remained toothless; and it brought no progress towards an Atlantic concert.

Nonetheless, the search for a conclusive postwar settlement continued – and led to the last major success of Locarno politics, achieved through the last transatlantic ‘grand bargain’ of the 1920s. At the first Hague conference in August 1929, a comprehensive ‘final’ reparations agreement was hammered out, based on the US-authored Young Plan; and a Rhineland compromise was forged, which stipulated that the occupation would end in June 1930, significantly earlier than the 1935 deadline set at Versailles.

With the benefit of hindsight, it becomes clear that the fledgling Locarno system only had a very short time to take root – between 1925 and the autumn of 1929, when Stresemann’s premature death foreshadowed future storms. Ultimately, the Locarno concert simply could not be made sufficiently resilient, or sufficiently expanded, to cope with the massive shockwaves of the World Economic Crisis. This crisis, which originated not with Locarno politics but rather with US-style laissez-faire capitalism, soon escalated into a global political earthquake. The Locarno system corroded when all relevant powers, and chiefly the United States, eschewed concerted crisis-management and instead turned to national ‘self-help’ policies. And it disintegrated when the deepening depression and fatal austerity policies of Brüning and his successors caused the collapse of the Weimar Republic – and the remaining Locarno powers had no capacity to preserve the European concert. This empowered Hitler to destroy the order of the 1920s.

It is critical to stress again, however, that the new dawn of Locarno had not set the stage for the triumph of the dark in the 1930s. Locarno-style peace-building with the representatives of a republican Germany and an emphasis on concerted approaches and common peace-enforcing ground-rules stands in marked contrast to the misguided ‘appeasement’ policies of Munich. For the latter rewarded Hitler, who in 1936 had demonstratively broken the Locarno treaty when remilitarising the Rhineland, with futile concessions, made at the expense of Czechoslovakia, that only encouraged him to pursue even more aggressive expansionism, eventually conclude the ominous pact with Stalin, and ultimately unleash an even more horrendous global war.

Yet the achievements of the Locarno era should be seen as a significant precursor in a different, much wider context – namely for the more successful efforts to found a sustainable Atlantic peace order after the Second World War, first in the west, then – after 1989 – also in the east. They prefigured the concerted efforts that later advanced West European integration and created a novel Atlantic community on the pillars of the Marshall Plan and the North Atlantic Alliance. They also anticipated the Helsinki process and, later, post-Cold War aspirations to establish an integrative peace system through the Organisation for Security and Co-operation in Europe.

To a greater or lesser degree, all these efforts can be seen as bids to learn from what was and what was not accomplished in the 1920s. And we still have much to learn from this today, at a time when the unfinished rule-based peace order of the long 20th century threatens to be undermined both from without and within.