The Road to War

The European war began with Germany's invasion of Poland on 1 September 1939, but its origins cannot be contained within the final weeks of peace. Japan had occupied Manchuria eight years earlier and had been at war with China since 1937. Italy had conquered Abyssinia. Germany had restored conscription, rebuilt its armed forces, remilitarised the Rhineland and overturned much of the territorial settlement imposed after the First World War.

None of those developments made another world war inevitable. They did, however, change what governments believed they could risk. Measures intended to preserve peace, League of Nations pressure, sanctions, diplomatic agreements, non-intervention and territorial concessions repeatedly failed either to reverse aggression or to convince the aggressor that the next move would meet effective resistance.

The road to September 1939 therefore runs through a series of decisions rather than a simple countdown to war: the settlement reached at Versailles, the economic and political shocks of the interwar years, Japanese expansion in China, Mussolini's attack on Abyssinia, German rearmament and the Rhineland, foreign intervention in Spain, the annexation of Austria, the destruction of Czechoslovakia, and finally the German-Soviet pact that removed one of the immediate obstacles to an attack on Poland.

At each stage, the choices available became narrower and more dangerous. The important question is not why governments failed to stop a war whose future course they could already see. It is what they understood at the time, what they feared would happen if they acted, and why the choices that appeared defensible in one crisis helped create a more difficult crisis after it.

Appeasement is often judged from the knowledge that war followed a year later. In 1938, British and French governments were making decisions without knowing how far Hitler would go, whether Germany could be deterred, or whether another European war would remain limited.

Britain was still rearming and was not prepared for a large continental commitment. Its defence planners were especially concerned about German air power, the vulnerability of British cities, imperial commitments, and the possibility that a European war could widen to include Italy or Japan. France had a much larger army, but its government was reluctant to confront Germany without firm British support.

Czechoslovakia was not defenceless. Its army was mobilised, its western frontier contained substantial fortifications, and much of its armaments industry lay within the territory threatened by Germany. For those who opposed further concessions, this was precisely the moment to draw a line: Germany was stronger than it had been during the Rhineland crisis of 1936, but it was not yet in the military position it would occupy after absorbing Austrian and Czech territory.

The Rhineland had already shown how much Hitler was prepared to risk. When German troops entered the demilitarised zone in March 1936, the forces committed were not strong enough to withstand a determined French military response. German commanders feared intervention, and Hitler later acknowledged the danger. France protested but did not act without British backing.

By 1938 the calculation was harder. British leaders believed that delay could buy time for rearmament, particularly in air defence. Their critics argued that delay also strengthened Germany. The annexation of Austria had already expanded German manpower and territory. Acquiring the Sudetenland would weaken Czechoslovakia's defensive position and give Germany access to additional industry and strategic depth.

There was also opposition to Hitler inside the German military. Officers including Ludwig Beck, Hans Oster and others discussed removing him if an attack on Czechoslovakia triggered a wider European war. Their plans depended on Hitler appearing to lead Germany toward military disaster. The Munich settlement removed that immediate danger and strengthened his position instead.

The argument over appeasement was therefore not between people who wanted peace and people who wanted war. Both sides believed they were trying to prevent a larger disaster. The disagreement was over timing.

Chamberlain and his supporters believed that Britain needed more time and that another territorial settlement might satisfy German demands without a general war. Their opponents believed that each successful challenge made the next one more dangerous and that Germany would become harder to stop after gaining additional territory, industry and strategic positions.

Munich did postpone war. It also left Germany in a stronger position when the next crisis came.

Much of the struggle over the European order before 1939 took place through treaties, diplomatic agreements and decisions about which rules would still be enforced. The Treaty of Versailles restricted German armed forces and prohibited an air force. The League of Nations was intended to provide collective security. During the 1930s, both systems were repeatedly challenged, modified or bypassed.

Germany began rebuilding its armed forces before openly abandoning the Versailles restrictions. In March 1935 Hitler announced the creation of the Luftwaffe and restored conscription, establishing an army far larger than the treaty permitted. Britain responded three months later with the Anglo-German Naval Agreement, accepting a German fleet limited principally by its size relative to the Royal Navy. The agreement was intended in London as a way of controlling German naval expansion, but it also showed that major provisions of Versailles could now be revised through direct negotiation with Germany.

The same tension appeared whenever an agreement was used to contain a crisis. Diplomacy could produce an immediate settlement without resolving the question behind it. Recognition of German rearmament was followed by the remilitarisation of the Rhineland; the Munich Agreement transferred the Sudetenland to Germany but did not preserve the rest of Czechoslovakia for long. In March 1939 German troops entered Prague and the remaining Czech lands were placed under German control.

The most consequential agreement came on 23 August 1939. Germany and the Soviet Union publicly signed a non-aggression pact. A secret protocol divided much of eastern Europe into German and Soviet spheres of influence and provided for the partition of Poland. The public agreement reduced Hitler's immediate risk of fighting the Soviet Union while attacking Poland; the secret protocol established how the two powers expected to divide territory after the attack.

Military preparation changed the balance alongside diplomacy. German rearmament expanded rapidly after 1935, but it did not produce an overwhelming military advantage at once. France invested heavily in the Maginot Line to protect its eastern frontier and force a German attack toward Belgium, where French forces expected to meet it. The failure of 1940 was therefore not simply that France had fortified the wrong border. French strategy depended on assumptions about where the main German attack would come, how quickly Allied armies could move into Belgium, and whether the Ardennes could carry a major armoured offensive.

By 1939, the treaties written after the First World War had not disappeared. What had changed was confidence that their restrictions would be enforced. Each successful revision altered the military balance and made the next diplomatic settlement harder to separate from the question of force.

When Germany invaded Poland on 1 September 1939, large-scale war and state violence were already underway elsewhere. Japan had been fighting a full-scale war in China since July 1937. The conflict brought major battles at Shanghai, Nanjing, Wuhan and elsewhere, together with bombing, displacement and mass killing. At Nanjing alone, Japanese forces killed an estimated 200,000 to 300,000 Chinese civilians and prisoners of war after taking the city in December 1937.

Italy's conquest of Abyssinia had begun in October 1935. Italian forces used chemical weapons, including mustard gas, despite Italy's obligations under the Geneva Protocol. The League of Nations imposed sanctions but failed to stop the campaign, and Addis Ababa fell in May 1936.

Spain then entered a three-year civil war in July 1936. German and Italian forces supported the Nationalists, while the Soviet Union assisted the Republic and foreign volunteers joined the International Brigades. About 500,000 people died during the conflict, including roughly 200,000 killed through executions, political violence and other atrocities away from the battlefield.

At the same time, Nazi persecution inside Germany was becoming progressively more systematic. Jewish civil servants and professionals were pushed from public life after 1933. The Nuremberg Laws of 1935 stripped German Jews of citizenship and prohibited marriage and sexual relations between Jews and people classified as German or related blood. After the annexation of Austria in March 1938, another large Jewish population came under Nazi rule.

The violence became overt during the November 1938 pogrom known as Kristallnacht. Synagogues were burned, Jewish businesses and homes were destroyed, Jews were murdered, and approximately 30,000 Jewish men were arrested and sent to concentration camps. Emigration accelerated, but finding a country willing to admit refugees became increasingly difficult.

By September 1939, approximately 282,000 Jews had emigrated from Germany and another 117,000 from annexed Austria. Many had left behind property, businesses and relatives; others remained because they could not obtain visas or afford to leave.

The international limits on escape had been visible at the Evian Conference in July 1938. Delegates from 32 countries met to discuss the growing refugee crisis, but most governments refused to expand their immigration quotas substantially. The conference created an international committee to continue negotiations, yet it produced little immediate relief for the people trying to leave Germany and Austria.

September 1939 was therefore not the point at which political violence suddenly became war. By then, parts of Asia, Africa and Europe had already experienced invasion, occupation, aerial bombing, chemical warfare, political execution, mass displacement and organised racial persecution. What changed with the invasion of Poland was the scale and geography of the conflict.

There is no single point on this chronology at which a different decision can be proved to have prevented the Second World War. The Rhineland crisis of 1936 remains one of the strongest counterfactuals because Germany was militarily weaker than it would later become and German leaders themselves understood the danger of French intervention. A French move might have forced a withdrawal. The further claim that it would necessarily have overthrown Hitler or permanently ended German expansion goes beyond what the evidence can establish.

Munich presents a different calculation. Czechoslovakia had mobilised, possessed strong frontier positions and could field a substantial army, while sections of the German officer corps feared that an attack might trigger a wider war before Germany was ready. Britain, however, believed important elements of its own rearmament were incomplete, and France was unwilling to fight without British support. Choosing resistance in 1938 would have meant deliberately accepting the possibility of a major European war, not simply calling a bluff at no cost.

Appeasement also produced gains and losses at the same time. The additional year allowed Britain to expand fighter production, radar coverage, anti-aircraft defence and other preparations. Germany used the same period to absorb territory, resources, Czech equipment and a stronger strategic position. Neither side received time alone.

The useful historical question is therefore not whether leaders in 1936 or 1938 should have known exactly what would happen in 1939 and 1940. It is how each settlement altered the risks of the next crisis. By March 1939 Britain had moved from concession toward an explicit guarantee of Polish independence, but deterrence still depended on convincing Hitler that the guarantee would be acted upon. It did not.

The British cabinet papers and chiefs of staff assessments are at Kew and are the best evidence for what the government believed about its own readiness. The German diplomatic record is in the captured files published as Documents on German Foreign Policy, and the Hossbach memorandum of November 1937 records Hitler setting out his intentions to his own commanders.

The secret protocol to the Molotov-Ribbentrop Pact was denied by the Soviet Union until 1989. The copy used at Nuremberg came from German microfilm.