History
Causes of World War II — quick study summary
World War II (1939–1945) had multiple interlocking causes. The Treaty of Versailles (1919) humiliated Germany with reparations and territorial losses, fuelling resentment. The Great Depression (1929) destabilised democracies and let extremist movements rise. Hitler's Nazi Party came to power in 1933 promising to reverse Versailles. The League of Nations failed to stop aggressive moves by Japan (Manchuria 1931), Italy (Ethiopia 1935), and Germany (Rhineland 1936, Austria 1938, Czechoslovakia 1938–39). Britain and France's appeasement emboldened Hitler. War began when Germany invaded Poland on 1 September 1939.
Key points
- Treaty of Versailles (1919): harsh terms on Germany — reparations, lost territory, war-guilt clause
- Great Depression (1929): economic collapse weakened democracies, enabled extremism
- Hitler chancellor 1933; rearmament from 1935 in violation of Versailles
- Aggression unchecked: Japan-Manchuria 1931, Italy-Ethiopia 1935, Rhineland 1936, Anschluss 1938, Sudetenland 1938
- Appeasement (Munich 1938) failed; war declared after Germany invaded Poland 1 Sept 1939
Practice quiz
Click each question to reveal the answer.
1. What treaty's harsh terms on Germany are often cited as a long-term cause of WWII?
- Treaty of Versailles (1919)
- Treaty of Trianon
- Munich Agreement
- Locarno Treaty
Answer: Treaty of Versailles (1919)
The Versailles treaty's reparations, territorial losses, and 'war guilt' clause fuelled lasting German resentment.
2. What policy did Britain and France use to try to avoid war with Hitler in the late 1930s?
Answer: Appeasement
They allowed Hitler's expansion (Rhineland, Austria, Sudetenland) hoping to satisfy his demands — most famously at the Munich Conference in 1938.
3. What event triggered the official declaration of WWII in Europe?
Answer: Germany's invasion of Poland on 1 September 1939
Britain and France had guaranteed Poland's independence; when Germany invaded, they declared war on 3 September 1939.
Last reviewed: May 2026