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Causes of World War II: From Versailles to the Invasion of Poland

What caused World War II: the Versailles settlement, the Depression, Nazi expansion, Japan and Italy, appeasement at Munich and the Nazi–Soviet pact of 1939.

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Key takeaways

  • Wikipedia names the immediate trigger as Germany's invasion of Poland on 1 September 1939 and the British and French declarations of war that followed.
  • Article 231 of the Treaty of Versailles had Germany accept responsibility for the loss and damage of the First World War, the basis for reparations.
  • Wikipedia says the Depression led many to lose faith in liberal democracy; the Nazis took totalitarian power in Germany from 1933.
  • The Munich Agreement of 29 September 1938 set German occupation of the Sudetenland in stages between 1 and 10 October; Germany took Prague in March 1939.
  • The Nazi–Soviet treaty was signed in Moscow on 23 August 1939, nine days before the invasion; its secret protocol divided Eastern Europe into spheres.

The Second World War in Europe was triggered by Germany's invasion of Poland on 1 September 1939 and the declarations of war by Britain and France that followed. Behind that trigger, historians point to a chain running back twenty years: a peace settlement that Germans bitterly resented, a world depression that discredited democracy, the Nazi seizure of power in 1933, aggression by Germany, Italy and Japan that the League of Nations could not stop, a policy of appeasement that peaked at Munich in 1938, and a pact between Hitler and Stalin that cleared the way for the attack on Poland.

Wikipedia separates these into "ultimate" and "proximate" causes. This page follows the same split, using three of the documents themselves — the Versailles reparation clauses, the Munich agreement and the Nazi–Soviet treaty — as transcribed by Yale's Avalon Project.

Versailles and the war-guilt clause

The 1919 Treaty of Versailles, Wikipedia says, punished Germany with heavy reparations and limits on its military, demilitarised the Rhineland, banned union with Austria and took away its colonies and about 12% of its pre-war land and population. Wikipedia notes these terms provoked "strong currents of revanchism" — a desire to reverse them.

The clause that carried the moral weight was Article 231. In the Avalon Project's text, the Allies "affirm and Germany accepts the responsibility of Germany and her allies for causing all the loss and damage" suffered "as a consequence of the war imposed upon them by the aggression of Germany and her allies." Article 232 then concedes that Germany's resources "are not adequate" to make complete reparation. Read as a primary source, the pair is striking: one article assigns total responsibility, the next admits total payment is impossible.

Wikipedia records that the treaty was criticised from all sides as neither lenient enough to appease Germany nor harsh enough to stop it becoming a dominant power again. How the first war started is a separate question, treated in what started the First World War.

The Depression and the Nazi state

The Great Depression of the 1930s, Wikipedia says, led many people to lose faith in liberal democracy, and countries across the world turned to authoritarian regimes. In Germany it combined with resentment of Versailles and a splintered party system. The Nazis took totalitarian power from 1933 and demanded the undoing of Versailles; Wikipedia lists the ideological drivers of their policy as antisemitism, the unification of all Germans, the acquisition of "living space" in the east, the elimination of Bolshevism and a racial hierarchy that cast Jews and Slavs as "subhumans."

Aggression the League could not stop, 1931–1938

The pattern of the 1930s was aggression met by weak responses. Wikipedia lists the steps:

Year Event
1931 Japan stages the Mukden Incident and sets up the puppet state of Manchukuo
1935–36 Italy invades Ethiopia; League sanctions prove ineffective; annexation in May 1936
7 March 1936 Germany remilitarises the Rhineland in breach of Versailles; neither France nor Britain acts
1936–39 Spanish Civil War: Germany and Italy back Franco's Nationalists, the Soviet Union backs the Republic
1937 The Marco Polo Bridge Incident begins the Second Sino-Japanese War
1938 The Anschluss annexes Austria to Germany by threat of force

Wikipedia judges that the League "proved helpless, especially regarding China and Ethiopia."

Munich, 29 September 1938

The Sudetenland, Wikipedia notes, was a mostly German-speaking border region of Czechoslovakia with more than three million ethnic Germans. The agreement signed at Munich on 29 September 1938 by Germany, Britain, France and Italy handed it over on a timetable. The Avalon text sets out that evacuation would begin on 1 October and be completed by 10 October, with German troops occupying four marked zones in turn — zone I on 1–2 October through zone IV on 6–7 October — and the remainder by the 10th. Counting 1 to 10 October inclusive, that is ten days for the whole transfer.

Hitler called it his last territorial claim. In March 1939 German troops entered Prague and Czechoslovakia ceased to exist; Wikipedia says this ended the British and French policy of appeasement, and the two powers decided any further German expansion would be met by force.

Poland, Danzig and the Nazi–Soviet pact

Poland was the next target. Hitler demanded a change in the status of the Free City of Danzig and an extraterritorial road across Polish territory; Poland refused. Wikipedia quotes Hitler telling his generals on 23 May 1939 that "Danzig is not the issue at stake. It is a matter of extending our living space in the East." Britain and France announced that an invasion would mean war.

The decisive diplomatic move came from Moscow. The treaty signed there on 23 August 1939 reads, in the Avalon text, as a plain non-aggression pact: neither side would attack the other or support a third power attacking it, and it was "concluded for a period of ten years." Wikipedia explains what the public text left out — a secret protocol dividing Finland, Estonia, Latvia, Lithuania, Poland and Romania into German and Soviet spheres. Germany invaded Poland nine days later, on 1 September; the Red Army entered from the east on 17 September. The ten-year treaty lasted less than two years: Germany attacked the Soviet Union in June 1941.

Intention or crisis? The historians' argument

Wikipedia describes a late-1980s dispute between Timothy Mason and Richard Overy. Mason argued that an overheated rearmament economy and working-class pressure forced Hitler into a "flight into war" at a time not of his choosing. Overy replied that Germany's economic problems in 1939 could not explain the attack on Poland, and that the war came from choices made by the Nazi leadership. Mason himself accepted that "Nazi Germany was always bent at some time upon a major war of expansion"; his argument was about timing and what drove it.

The war's human cost is set out, with its uncertainties, in why the Second World War death toll is given as a range. World History Timeline Sim, our app, lets you place 1919, 1933, 1938 and 1939 on one timeline and browse by region. Its what-if mode is a simulation, not a record, and the app is a companion to coursework. More history guides sit under education and brain training.

Good to know

Frequently asked questions

What did Article 231 of the Treaty of Versailles say?
In the text transcribed by Yale's Avalon Project, the Allies affirmed and Germany accepted 'the responsibility of Germany and her allies for causing all the loss and damage' suffered by the Allies 'as a consequence of the war imposed upon them by the aggression of Germany and her allies'. Wikipedia notes this War Guilt Clause was the basis for reparations, and that Germans largely saw the treaty as placing the blame on them.
What was appeasement and why did it fail?
The policy of meeting German demands to avoid war. Wikipedia describes the responses to aggression in the 1930s as feeble and ineffectual, with the Munich Conference of 1938 approving Germany's annexation of the Sudetenland. Hitler called it his last territorial claim, but in March 1939 German troops took Prague, which Wikipedia says ended the French and British policy of appeasement.
Did Germany's economy force Hitler into war in 1939?
Historians have argued over it. Wikipedia describes a late-1980s debate in which Timothy Mason argued that a structural economic crisis imposed a 'flight into war', while Richard Overy replied that Germany's economic problems could not explain the attack on Poland and that the war resulted from choices made by the Nazi leadership.
How did the Molotov–Ribbentrop Pact lead to war?
Signed in Moscow on 23 August 1939, it was publicly a ten-year non-aggression treaty. Wikipedia says its secret protocol divided Finland, the Baltic states, Poland and Romania into German and Soviet spheres and helped make the invasion of Poland possible. Germany invaded on 1 September and the Soviet Union entered eastern Poland on 17 September.

Sources

  1. The Versailles Treaty, June 28, 1919: Part VIII (Reparation) (opens in a new tab)The Avalon Project, Yale Law School — accessed
  2. Munich Pact, September 29, 1938 (opens in a new tab)The Avalon Project, Yale Law School — accessed
  3. Treaty of Nonaggression Between Germany and the Union of Soviet Socialist Republics (opens in a new tab)The Avalon Project, Yale Law School — accessed
  4. Causes of World War II (opens in a new tab)Wikipedia — accessed

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