How an International Order Died: Lessons from the Interwar Era


In the late 1920s, a group of German officers stood side by side at a range, practicing their marksmanship by firing at target dummies dressed in Polish and Czech military uniforms. Standing next to them, and firing at the same targets, were Red Army officers. They were taking a training course together at one of the four joint German-Soviet military bases that were established on Soviet territory beginning in 1925. The German military used the bases to develop and test new technologies of war, train a new generation of military officers, and develop innovative tactics away from the prying eyes of the British and French inspection teams then in Germany. For their communist counterparts, German help meant modernizing and professionalizing the Soviet military.

Such military cooperation was at the heart of nearly 20 years of intermittent collaboration between German and Soviet leaders during the period between World War I and World War II. The partnership was built upon a shared interest in destroying the existing international order, and it would culminate in the return of Europe to war. That moment would arrive before dawn on Sept. 1, 1939, as the German air force unleashed terror bombing against more than 150 towns and cities across the western portion of Poland. Without a declaration of war, 50 divisions of the reborn German army soon crossed the Polish frontier. Sixteen days later, as Poland battled for its life, the Polish ambassador was summoned to the Kremlin in Moscow, where he was informed, “The Soviet government intends to ‘liberate’ the Polish people from the unfortunate war.” A few hours later, 600,000 Red Army soldiers crossed the Polish frontier from the east.



Policymakers and analysts should study the collapse of the interwar order because that era was the most recent period of true multipolarity in the international system. With the return of multipolarity, the interregnum between World War I and World War II is increasingly relevant as a source of historical analogies. In addition, the question of deterring revisionist states — particularly through non-nuclear means — is a major concern of American security and defense policy today. Examining how and why deterrence failed to maintain the status quo in Europe in 1939 — despite the seeming superiority of British, French, and Polish forces — offers useful lessons about the nature of conventional deterrence and the prospects for conflict in the increasingly dynamic contemporary world.

The Post-World War I International Order 

Shifts in global order tend to become apparent only at their end. Contemporaries, and many historians, place considerable blame for World War II on the statesmen present at Munich in 1938. In fact, the deterioration of the order established at Versailles had begun almost immediately in 1919, and was largely complete by 1936. By that juncture, Germany, the Soviet Union, and other regional powers had undermined the foundations of the status quo, with the aim of establishing their own versions of regional and global order in its stead. 

To understand how German and Soviet leaders destroyed the interwar international order, it is necessary to see what constituted that order. Its most ambitious components were the product of America’s role in final victory in World War I, which provided President Woodrow Wilson with the leverage to demand a new international system. He aimed to replace the power politics he deemed responsible for the outbreak of the war with what would become known as “liberal internationalism.”

The core elements of the new order Wilson demanded included collective security, a decrease in armaments, free trade, recognition of the equality of sovereign states, and the promotion of self-determination. All of these measures were contested in practice among the victors of World War I, particularly after the precipitous American military withdrawal and diplomatic disengagement from Europe. In broad strokes, however, Wilson’s principles shaped the peace settlement: The League of Nations charter, which was a major part of the Treaty of Versailles produced at the Paris Peace Conference, included a mandate to “promote international co-operation and to achieve international peace and security.” While Germany was disarmed as part of the dictated terms of peace, the Allies made clear that they envisioned this as only the first step toward a general disarmament of Europe that would include the victors too. In addition, the principle of self-determination, extended primarily in Eastern Europe, led to the creation of new, sovereign nation-states, most importantly Poland and Czechoslovakia.

German and Soviet Opposition to the Interwar Order 

Factions in both Germany and the Soviet state — which had been established as a result of the 1917 Bolshevik Revolution — were united in opposing almost all elements of the new order, a fact that became apparent almost immediately. The German military initiated quiet diplomacy with the Bolshevik leadership in Moscow even before the Treaty of Versailles had been finalized. German violations of that treaty, in the form of secret rearmament measures and resistance to reparations, began essentially as soon as it was ratified. In 1922, with the enthusiastic assent of Leon Trotsky — then head of the Red Army — the German military began relocating banned military-industrial production to secret facilities in the Soviet Union. The aim was clear and fundamentally revisionist — in the words of German Gen. Hans von Seeckt, head of the Army Command from 1920 to 1926, “Poland must and will be wiped off the map.”

In 1926, a journalist at the Manchester Guardian revealed some of the details of the German military’s covert rearmament measures in the Soviet Union, of which the civilian government in Berlin was only partially aware. During the public furor that followed in the German parliament, representatives on the right tried to shout down anyone speaking against rearmament. Others gestured toward the American ambassador, who was observing the proceedings from the diplomatic box, and shouted, “Why reveal these things to our enemies?!” The result was a vote of no confidence in the sitting chancellor, but that ushered in a government only further to the political right. It would oversee an expansion of the covert work conducted in Russia. As a result, by the end of 1932 — before Adolf Hitler came to power — then-Chancellor Kurt von Schleicher had already begun to expand the German army to 21 divisions, well beyond the limits set by the Versailles Treaty. And Germany had kept pace technologically with its rivals in critical areas, including tanks, aircraft, military radios, and chemical weapons.

British and French Reluctance to Defend the Order     

Defending the international order in the face of this challenge was made much more difficult by doubts among British and French policymakers regarding its value. British Prime Minister Ramsay MacDonald went so far as to call the Treaty of Versailles “a blot on the peace of the world” in 1933. Tensions between national interests and international commitments confounded British and French leaders. Clear contradictions in the application of self-determination — both within Europe and across European empires — further undermined claims to high principle. And the unwillingness of the French and British publics to support significant military forces in peacetime made punishing minor violations of the Versailles Treaty difficult, even for far-sighted statesmen like Sir Robert Vansittart, the permanent undersecretary at the U.K. Foreign Office.

Limited by these handicaps, the ways in which British and French policymakers did attempt to defend the status quo in Europe were problematic. They were well aware that the order’s biggest problem was that the League of Nations and the Paris Peace Conference treaties did not include or satisfy six of the world’s eight largest economies: the United States, China, Germany, the Soviet Union, Italy, and Japan. To remedy that, leaders in Great Britain and France hoped to draw the United States into engagement with the European financial and security system in a variety of ways, but they met with limited success. They also hoped to incorporate Germany into the order through trade and the gradual amelioration of its reparations payments. The Soviet Union was seen initially as a certain adversary, but that attitude mellowed in London and Paris over time.

As it turned out, these approaches to Germany and the Soviet Union rested on a series of false assumptions and misunderstandings. Both Stanley Baldwin and MacDonald, who were members of the Conservative and Labour parties respectively and served as prime ministers of Great Britain in alternating periods from 1924 to 1937, believed in the logic of engagement. They assumed that reintegrating Germany into the global trade system and incorporating it into institutions like the League of Nations would further liberalize its society and strengthen representative government in the country.

To a degree, that project seemed to be working through the onset of the Great Depression in 1929. But at the same time, while they publicly supported such efforts, the Weimar Republic’s leading politicians simultaneously sought drastic revision of Germany’s place in the international order — including through the redrawing of borders across Central Europe. Even the great Weimar statesman, and Nobel Peace Prize laureate, Gustav Stresemann favored territorial revision and privately encouraged illegal German rearmament. As a result, between 1922 and 1932, German violations of Versailles continuously grew in scope and scale, while German political leaders still seemed rhetorically committed to partnership with the enforcers of the treaty. Consequently, the British response to secret German rearmament measures was one of confusion. London pushed for French disarmament, which was seen by many in Britain as the legitimate source of German security fears. But this only further emboldened German proponents of rearmament and the revision of the country’s borders by force.

British and French attempts to “liberalize” the Soviet political system through commerce and integration proceeded more cautiously, a consequence of ideological suspicions. But soon after the October Revolution, the Soviet Union resumed foreign trade on a large scale, and in 1934 it was invited to join the League of Nations. Throughout this period, foreign statesmen believed that trade and integration into international institutions would moderate the Soviet regime. Even the Soviet Union’s German military partners — most of whom were hardly sympathetic to liberalism — incorrectly believed that economic engagement would bring about political change in Moscow. In 1922, Seeckt proposed expanding trade with Russia to “undermine the very idea of the Soviet system by making sound alternatives available.” The opposite occurred. Soviet leader Josef Stalin eliminated the relatively market-friendly New Economic Policy in 1928 and embarked on an extraordinarily violent program of collectivization to produce grain for export. The aim was to generate revenue that would pay for machine tools and military equipment.

Attempts to integrate Germany and the Soviet Union into the international trade system failed to change the political aspirations of key decision-makers in those countries and, in the process, helped to strengthen their future capacities for waging war. By the mid-1930s, the increasing strength of revisionist states in Europe and Asia made clear the incompatibility of their interests with the existing order. When Hitler openly announced rearmament in March 1935 — thus challenging the Treaty of Versailles publicly — Italy, France, and Great Britain attempted to use the League of Nations to contain Germany. Known as the Stresa Front, their coalition fell apart within weeks. In an attempt to salvage containment, the French government acquiesced to the Italian invasion of Ethiopia, long desired by dictator Benito Mussolini. This blatant violation of the League of Nations charter threw that body into chaos, revealing its impotence. More generally, the entire process made a mockery of the principles of collective security, and the broader ideals that had supposedly been enshrined in the League’s founding document. Unwilling to defend the European order in 1935, the British and French governments “paddled in a puree of words” while doing nothing as Hitler remilitarized the Rhineland and annexed Austria. Negotiations in London in 1935, and at Munich in 1938, aimed to defer conflict as long as possible, but did little to resolve the growing challenge from Germany.

The Final Collapse

By the summer of 1939, there was little left of the old order. Hopes for Europe-wide disarmament were clearly gone and the League of Nations was effectively defunct. But the end of the old order did not inevitably mean the end of peace. At the beginning of August 1939, the French and British militaries were well along in their own rearmament programs, rapidly catching up with Germany. Together, they could mobilize more men than Germany and, considered jointly with their empires, had significantly larger economic capacity for war. Germany lacked the resources to sustain a long war, and was short on oil, iron, coal, and even food. On the face of it, even with the repeated failures to enforce the treaties, rules, and norms established at the Paris Peace Conference, Europe might have remained at peace. The preponderance of military power, at least according to traditional measures, seemed to be in the hands of Great Britain, France, and their partners.

Why then did war break out in 1939? As John Mearsheimer has argued, conventional deterrence often breaks down when policymakers in one state think that changes in the material balance of power offer them the prospect of a quick and decisive victory. Hitler believed exactly that. In November 1937, Hitler told his military leadership that Germany must initiate the next war soon, as Germany had a lead in the development of weapons, and delaying war meant “the danger of their obsolescence.” Hitler’s confidante Albert Speer also recounted how the Nazi leader believed war needed to come sooner rather than later, citing Germany’s “proportional superiority” in weapons technology, which would “constantly diminish” from 1940 onward. In Hitler’s mind, new technologies of war, deployed in innovative ways, offered a key to victory. They made the traditional balance of power, in terms of raw manpower and gross domestic product, irrelevant. It was this perception, along with uncertainty about British and French willingness to defend the existing order after 15 years of permitting German rearmament, that led to the breakdown of conventional deterrence. Hitler believed he could deter British intervention and achieve a rapid victory against Poland in 1939. Germany’s fleeting lead in the arms race, the perceived weaknesses of his rivals, and his partnerships with Italy, Japan, and the Soviet Union all suggested another bloodless victory. But to Hitler’s surprise, Great Britain and France honored their pledges to Poland, and Europe found itself at war once again.

Lessons for Today?

The collapse of the interwar international order, and the failure of conventional deterrence at its end, resulted in a new war more terrible than any before in human history. What are the key lessons of that disaster? The most obvious is that states opposed to an existing international order may work together despite historical enmity or ideological hostility. Though the Soviet Union and Germany had vastly different visions of their preferred order, they collaborated because their opposition to the status quo was greater than their concerns about each other.

The Western democracies also failed the admittedly tough challenge of defending the existing order, lacking the necessary resolve, unity, and strength. Weak resolve resulted partly from a sense of hypocrisy — British and French leaders themselves undermined the stability of the post-World War I order by violating its precepts of self-determination, collective security, and disarmament. As Lloyd George, who had been British prime minister at the time of the Paris Peace Conference, bemoaned in 1935, Great Britain and France were “in no position morally to enforce those parts of the treaty which they themselves have flagrantly and defiantly broken.” Much of the political spectrum in London agreed.

The unclear resolve of likely adversaries, willing revisionist partners, and revolutionary technological change combined to convince Hitler he could win a new war. There is a risk that similar factors could embolden revisionist leaders today or in the near future. Changes in technology, some argue, represent a new “revolution in military affairs,” which could challenge the existing hierarchy of military power. The rise of autonomous weapons may dent American military predominance, as the expensive capital equipment that constitutes American conventional strength becomes increasingly vulnerable to cheaper autonomous systems. Questions also abound about whether offensive cyber warfare capabilities and anti-satellite technology might have similar effects. Simultaneously, there is growing uncertainty about the willingness and ability of the United States and its partners to defend the order established after World War II. Collectively, these factors may weaken conventional deterrence and suggest opportunities to potential revisionist powers like Russia and China, particularly if they believe that working in concert will deter American intervention.

During the interwar period, British and French leaders ended up encouraging revisionist powers by failing to maintain military forces capable of deterring them. It can be difficult for great powers, particularly democracies, to arm appropriately and quickly when new threats present themselves. French defeat in 1940 marked the end of a 20-year program by German military leaders, which only appeared from Paris to be an existential threat in 1936. Complacency in moments of deteriorating global order and uncertain technological change can mean the collapse of deterrence and, in some cases, disastrous defeat. Embracing imaginative, cutting-edge technology and doctrine in the face of enormous political and financial incentives to maintain legacy systems is one of the greatest challenges to maintaining military predominance. Failing to do so may open a “technological window,” where a revisionist power perceives an opportunity to win a limited war. Perhaps the lessons of the interwar period — rightly understood — may offer some guidance in avoiding such a catastrophe.



Ian Ona Johnson is the P.J. Moran Family Assistant Professor of Military History at the University of Notre Dame. He is the author of Faustian Bargain: The Soviet-German Partnership and the Origins of the Second World War (Oxford, June 2021).

Image: German Federal Archive (Bundesarchiv, Bild 102-10351 / CC-BY-SA 3.0)