Causes of World War II

Read this article on the origins of World War II. It provides a global perspective on the multiple causes and how each of the powers involved entered the conflict.

Ultimate Causes

Legacies of World War I


David Lloyd George of Britain, Vittorio Emanuele Orlando of Italy, Georges Clemenceau of France, Woodrow Wilson of the U.S.


"The Big Four" made all the major decisions at the Paris Peace Conference (from left to right, David Lloyd George of Britain, Vittorio Emanuele Orlando of Italy, Georges Clemenceau of France, Woodrow Wilson of the U.S.)


By the end of World War I in late 1918, the world's social and geopolitical circumstances had fundamentally and irrevocably changed. The Allies had been victorious, but many of Europe's economies and infrastructures had been devastated, including those of the victors. France, along with the other victors, was in a desperate situation regarding its economy, security and morale and understood that its position in 1918 was "artificial and transitory". Thus, French Prime Minister Georges Clemenceau worked to gain French security via the Treaty of Versailles, and French security demands, such as reparations, coal payments, and a demilitarised Rhineland, took precedence at the Paris Peace Conference of 1919–1920, which designed the treaty. The war "must be someone's fault – and that's a very natural human reaction", analysed the historian Margaret MacMillan.

Germany was charged with the sole responsibility of starting World War I, and the War Guilt Clause was the first step to satisfying revenge for the victor countries, especially France, against Germany. Roy H. Ginsberg argued, "France was greatly weakened and, in its weakness and fear of a resurgent Germany, sought to isolate and punish Germany.... French revenge would come back to haunt France during the Nazi invasion and occupation 20 years later".

Map of Germany after Versailles.


Germany after Versailles


The two main provisions of the French security agenda were war reparations from Germany in the form of money and coal and a detached German Rhineland. The French government printed excess currency, which created inflation, to compensate for the lack of funds, and it borrowed money from the United States. Reparations from Germany were needed to stabilise the French economy. France also demanded for Germany to give France its coal supply from the Ruhr to compensate for the destruction of French coal mines during the war.

The French demanded an amount of coal that was a "technical impossibility" for the Germans to pay. France also insisted on the demilitarisation of the German Rhineland in the hope of hindering any possibility of a future German attack and giving France a physical security barrier between itself and Germany. The inordinate amount of reparations, coal payments and the principle of a demilitarised Rhineland were largely viewed by the Germans as insulting and unreasonable.

The resulting Treaty of Versailles brought a formal end to the war but was judged by governments on all sides of the conflict. It was neither lenient enough to appease Germany nor harsh enough to prevent it from becoming a dominant continental power again. The German people largely viewed the treaty as placing the blame, or "war guilt", on Germany and Austria-Hungary and as punishing them for their "responsibility", rather than working out an agreement that would assure long-term peace. The treaty imposed harsh monetary reparations and requirements for demilitarisation and territorial dismemberment, caused mass ethnic resettlement and separated millions of ethnic Germans into neighbouring countries.

In the effort to pay war reparations to Britain and France, the Weimar Republic printed trillions of marks, which caused hyperinflation. Robert O. Paxton stated, "No postwar German government believed it could accept such a burden on future generations and survive...." Paying reparations to the victorious side had been a traditional punishment with a long history of use, but it was the "extreme immoderation" that caused German resentment. Germany did not make its last World War I reparation payment until 3 October 2010, 92 years after the end of the war.

Germany also fell behind its coal payments because of a passive resistance movement against France. In response, the French invaded the Ruhr and occupied it. By then, most Germans had become enraged with the French and placed the blame for their humiliation on the Weimar Republic. Adolf Hitler, a leader of the Nazi Party, attempted a coup d'état in 1923 in what became known as the Beer Hall Putsch, and he intended to establish a Greater Germanic Reich. Although he failed, Hitler gained recognition as a national hero by the German population.

During the war, German colonies outside Europe had been annexed by the Allies, and Italy took the southern half of Tyrol after the armistice. The war in the east had ended with the defeat and the collapse of the Russian Empire, and German troops had occupied large parts of Eastern and Central Europe with varying degrees of control and established various client states such as a kingdom of Poland and the United Baltic Duchy. The German Navy spent most of the war in port, only to be turned over to the Allies. It was scuttled by its own officers to avoid it from being surrendered. Decades later, the lack of an obvious military defeat would be one of the pillars holding together the Dolchstosslegende ("stab-in-the-back myth"), which gave the Nazis another propaganda tool.

Map of territorial changes in Europe after World War I (as of 1923)

Map of territorial changes in Europe after World War I (as of 1923)


The demilitarised Rhineland and the additional cutbacks on military also infuriated the Germans. Although France logically wanted the Rhineland to be a neutral zone, France had the power to make their desire happen, which merely exacerbated German resentment of the French. In addition, the Treaty of Versailles dissolved the German general staff, and possession of navy ships, aircraft, poison gas, tanks and heavy artillery was also made illegal. The humiliation of being bossed around by the victor countries, especially France, and being stripped of their prized military made the Germans resent the Weimar Republic and idolise anyone who stood up to it. Austria also found the treaty unjust, which encouraged Hitler's popularity.

The conditions generated bitter resentment towards the war's victors, who had promised the Germans that US President Woodrow Wilson's Fourteen Points would be a guideline for peace; but the Americans had played only a minor role in the war, and Wilson could not convince the Allies to agree to adopt his Fourteen Points. Many Germans felt that the German government had agreed to an armistice based on that understanding, and others felt that the German Revolution of 1918–1919 had been orchestrated by the "November criminals", who later assumed office in the new Weimar Republic.

The Japanese also started to express resentment against Western Europe for how they were treated during the negotiations of the Treaty of Versailles. The Japanese proposition to discuss the issue of racial equality was not put in the final draft because of many other Allies, and the Japanese participation in the war caused little reward for the country. The war's economic and psychological legacies persisted well into the Interwar period.


Failure of League of Nations

The League of Nations was an international peacekeeping organization founded in 1919 with the explicit goal of preventing future wars. The League's methods included disarmament, collective security, the settlement disputes between countries by negotiations and diplomacy and the improvement global welfare. The diplomatic philosophy behind the League represented a fundamental shift in thought from the preceding century. The old philosophy of "concert of nations", which grew out of the Congress of Vienna (1815), saw Europe as a shifting map of alliances among nation-states, which created a balance of power that was maintained by strong armies and secret agreements. Under the new philosophy, the League would act as a government of governments, with the role of settling disputes between individual nations in an open and legalist forum. Despite Wilson's advocacy, the United States never joined the League of Nations.

Photo of the official opening of the League of Nations.

The official opening of the League of Nations, 15 November 1920


The League lacked an armed force of its own and so depended on member nations to enforce its resolutions, uphold economic sanctions that the League ordered or provide an army when needed for the League to use. However, individual governments were often very reluctant to do so. After numerous notable successes and some early failures in the 1920s, the League ultimately proved incapable of preventing aggression by the Axis Powers in the 1930s. The reliance upon unanimous decisions, the lack of an independent body of armed forces and the continued self-interest of its leading members meant that the failure was arguably inevitable.


Expansionism and Militarism

Expansionism is the doctrine of expanding the territorial base or economic influence of a country, usually by means of military aggression. Militarism is the principle or policy of maintaining a strong military capability to use aggressively to expand national interests and/or values, with the view that military efficiency is the supreme ideal of a state.

The Treaty of Versailles and the League of Nations had sought to stifle expansionist and militarist policies by all actors, but the conditions imposed by their creators imposed on the world's new geopolitical situation and the technological circumstances of the era only emboldened the re-emergence of those ideologies during the Interwar Period. By the early 1930s, a militaristic and aggressive national ideology prevailed in Germany, Japan and Italy.

The attitude fuelled advancements in military technology, subversive propaganda and ultimately territorial expansion. It has been observed that the leaders of countries that have been suddenly militarised often feel a need to prove that their armies are formidable, which was often a contributing factor in the start of conflicts such as the Second Italo-Ethiopian War and the Second Sino-Japanese War.

In Italy, Benito Mussolini sought to create a New Roman Empire, based around the Mediterranean. Italy invaded Ethiopia as early as 1935, Albania in early 1938, and later Greece. The invasion of Ethiopia provoked angry words and a failed oil embargo from the League of Nations.

Under the Nazi regime, Germany began its own program of expansion that sought to restore its "rightful" boundaries. As a prelude toward its goals, the Rhineland was remilitarised in March 1936. Also of importance was the idea of a Greater Germany, supporters of which hoped to unite the German people under one nation-state to include all territories inhabited by Germans, even if they happened to be a minority in a particular territory. After the Treaty of Versailles, a unification between Germany and the newly formed German-Austria, a rump state of Austria-Hungary, was prohibited by the Allies, despite the large majority of Austrians supporting the idea.

During the Weimar Republic (1919–1933), the Kapp Putsch, an attempted coup d'état against the republican government, was launched by disaffected members of the armed forces. Later, some of the more radical militarists and nationalists were submerged in grief and despair into the Nazi Party, and more moderate elements of militarism declined. The result was an influx of militarily-inclined men into the Nazi Party. Combined with its racial theories, that fuelled irredentist sentiments and put Germany on a collision course for war with its immediate neighbours.

Photo of the Japanese march into Zhengyangmen, Beijing, after they captured the city in July 1937

The Japanese march into Zhengyangmen, Beijing, after they captured the city in July 1937


In Asia, the Empire of Japan harboured expansionist desires toward Manchuria and the Republic of China. Two contemporaneous factors in Japan contributed both to the growing power of its military and the chaos in its ranks before World War I. One was the Cabinet Law, which required the Imperial Japanese Army (IJA) and the Imperial Japanese Navy (IJN) to nominate cabinet members before changes could be formed. That essentially gave the military a veto power over the formation of any Cabinet in the ostensibly-parliamentary country.

The other factor was gekokujō, the institutionalized disobedience by junior officers. It was common for radical junior officers to press their goals to the extent of assassinating their seniors. In 1936, the phenomenon resulted in the February 26 Incident in which junior officers attempted a coup d'état and killed leading members of the Japanese government. In the 1930s, the Great Depression wrecked Japan's economy and gave radical elements within the Japanese military the chance to force the entire military into working towards the conquest of all of Asia.

For example, in 1931, the Kwantung Army, a Japanese military force stationed in Manchuria, staged the Mukden Incident, which sparked the invasion of Manchuria and its transformation into the Japanese puppet state of Manchukuo.


Germans vs. Slavs

Twentieth-century events marked the culmination of a millennium-long process of intermingling between Germans and Slavic people. The rise of nationalism in the 19th century made race a centerpiece of political loyalty. The rise of the nation-state had given way to the politics of identity, including pan-Germanism and pan-Slavism. Furthermore, Social Darwinist theories framed the coexistence as a "Teuton vs. Slav" struggle for domination, land, and limited resources. Integrating these ideas into their own worldview, the Nazis believed that the Germans, the "Aryan race", were the master race and that the Slavs were inferior.


Japan's Seizure of Resources and Markets


Map of Japanese occupation of Manchuria in northeast China in 1937

Japanese occupation of China in 1937


Other than a few coal and iron deposits and a small oil field on Sakhalin Island, Japan lacked strategic mineral resources. In the early 20th century, in the Russo-Japanese War, Japan had succeeded in pushing back the East Asian expansion of the Russian Empire in competition for Korea and Manchuria.

Japan's goal after 1931 was economic dominance of most of East Asia, often expressed in the Pan-Asian terms of "Asia for the Asians". Japan was determined to dominate the China market, which the US and other European powers had been dominating. On October 19, 1939, US Ambassador to Japan Joseph C. Grew, in a formal address to the America-Japan Society, stated that

the new order in East Asia has appeared to include, among other things, depriving Americans of their long established rights in China, and to this the American people are opposed.... American rights and interests in China are being impaired or destroyed by the policies and actions of the Japanese authorities in China.

In 1931, Japan invaded Manchuria and China proper. Under the guise of the Greater East Asia Co-Prosperity Sphere, with slogans such as "Asia for the Asians!", Japan sought to remove the Western powers' influence in China and replace it with Japanese domination.

The ongoing conflict in China led to a deepening conflict with the US in which public opinion was alarmed by events such as the Nanking Massacre and growing Japanese power. Lengthy talks were held between the US and Japan. The Japanese invasion of the south of French Indochina made President Franklin Roosevelt freeze all Japanese assets in the US. The intended consequence was to halt oil shipments from the US to Japan, which supplied 80 percent of Japanese oil imports. The Netherlands and Britain followed suit.

With oil reserves that would last only a year and a half during peacetime and much less during wartime, the ABCD line left Japan two choices: comply with the US-led demand to pull out of China or seize the oilfields in the East Indies from the Netherlands. The Japanese government deemed it unacceptable to retreat from China.


Mason-Overy Debate: "Flight into War" Theory

In the late 1980s, the British historian Richard Overy was involved in a historical dispute with Timothy Mason that played out mostly over the pages of the Past and Present journal over the reasons for the outbreak of the war in 1939. Mason had contended that a "flight into war" had been imposed on Hitler by a structural economic crisis, which confronted Hitler with the choice of making difficult economic decisions or aggression. Overy argued against Mason's thesis by maintaining that Germany was faced with economic problems in 1939, but the extent of those problems could not explain aggression against Poland and the reasons for the outbreak of war were the choices made by the Nazi leadership.

Mason had argued that the German working-class was always against the Nazi dictatorship; that in the overheated German economy of the late 1930s, German workers could force employers to grant higher wages by leaving for another firm and so grant the desired wage increases and that such a form of political resistance forced Hitler to go to war in 1939. Thus, the outbreak of the war was caused by structural economic problems, a "flight into war" imposed by a domestic crisis. The key aspects of the crisis were, according to Mason, a shaky economic recovery that was threatened by a rearmament program that overwhelmed the economy and in which the regime's nationalist bluster limited its options.

In that way, Mason articulated a Primat der Innenpolitik ("primacy of domestic politics") view of the war's origins by the concept of social imperialism. Mason's Primat der Innenpolitik thesis was in marked contrast to the Primat der Außenpolitik ("primacy of foreign politics"), which is usually used to explain the war. Mason thought German foreign policy was driven by domestic political considerations, and the launch the war in 1939 was best understood as a "barbaric variant of social imperialism".

Mason argued, "Nazi Germany was always bent at some time upon a major war of expansion". However, Mason argued that the timing of such a war was determined by domestic political pressures, especially as relating to a failing economy, and had nothing to do with what Hitler wanted. Mason believed that from 1936 to 1941, the state of the German economy, not Hitler's "will" or "intentions", was the most important determinate on German foreign policy decisions.

Mason argued that the Nazi leaders were so deeply haunted by the November 1918 German Revolution that they were most unwilling to see any fall in working-class living standards for fear of provoking a repetition of the revolution. Mason stated that by 1939, the "overheating" of the German economy caused by rearmament, the failure of various rearmament plans produced by the shortages of skilled workers, industrial unrest caused by the breakdown of German social policies and the sharp drop in living standards for the German working class forced Hitler into going to war at a time and a place that were not of his choosing.

Mason contended that when faced with the deep socio-economic crisis, the Nazi leadership had decided to embark upon a ruthless foreign policy of "smash and grab" to seize territory in Eastern Europe that could be pitilessly plundered to support the living standards in Germany. Mason described German foreign policy as driven by an opportunistic "next victim" syndrome after the Anschluss in which the "promiscuity of aggressive intentions" was nurtured by every successful foreign policy move. Mason's considered the decision to sign the Molotov–Ribbentrop Pact and to attack Poland despite the risk of a war against Britain and France to be the abandonment by Hitler of his foreign policy program outlined in Mein Kampf and to have been forced on him by his need to stop a collapsing German economy by seizing territory abroad to be plundered.

For Overy, the problem with Mason's thesis was that it rested on the assumption that in a way that was not shown by the records, information was passed on to Hitler about Germany's economic problems. Overy argued for a difference between economic pressures induced by the problems of the Four Year Plan and economic motives to seize raw materials, industry and foreign reserves of neighbouring states as a way of accelerating the plan. Overy asserted that Mason downplayed the repressive German state's capacity to deal with domestic unhappiness.

Finally, Overy argued that there is considerable evidence that Germany felt that it could master the economic problems of rearmament. As one civil servant put it in January 1940, "we have already mastered so many difficulties in the past, that here too, if one or other raw material became extremely scarce, ways and means will always yet be found to get out of a fix".