What were the main causes of the Second World War in Europe?

The main causes link together. The Treaty of Versailles left Germany resentful and gave Hitler grievances to exploit. The League of Nations failed to stop aggression in the 1930s, which encouraged the dictators. Hitler's aggressive foreign policy aimed to overturn Versailles, rearm Germany and expand, step by step. And the policy of appeasement by Britain and France let him get away with it until the invasion of Poland in 1939 finally brought war. A strong answer shows how these factors combined.

Why did the League of Nations fail to keep the peace?

The League failed for several reasons. It had no army of its own and relied on members to act. Important powers were absent, the United States never joined, and others left. Its main weapons, condemnation and economic sanctions, were slow and weak. The Great Depression made countries selfish and aggressive. When tested by Japan in Manchuria and Italy in Abyssinia, the League could not stop them, which exposed its weakness and encouraged Hitler to take risks.

What was the policy of appeasement and why did Britain and France follow it?

Appeasement meant giving in to some of Hitler's demands in the hope of avoiding war. Britain and France followed it for several reasons: the horror of the First World War made them desperate to avoid another, they were not ready militarily, some thought parts of the Treaty of Versailles had been too harsh, and many feared communism more than Hitler. The high point was the Munich Agreement of 1938, but when Hitler invaded the rest of Czechoslovakia and then Poland, appeasement was abandoned.

Why did the invasion of Poland lead to war in 1939?

By 1939 Britain and France had given up on appeasement after Hitler broke his promises by seizing the rest of Czechoslovakia, so they guaranteed Poland's independence. When Germany invaded Poland on 1 September 1939, Britain and France declared war. The Nazi-Soviet Pact had cleared the way for Hitler by removing the threat of war with the Soviet Union, so he gambled that the West would back down again, but this time it did not.

How is this topic assessed in N(A)-Level Humanities (History elective)?

History is examined within Combined Humanities (syllabus 2126), as the History elective alongside the compulsory Social Studies component. The current SEAB 2126 syllabus assesses the History elective through a source-based case study and structured-essay questions. The causes of the Second World War are a major essay topic, and the debate over whether Hitler, appeasement or the League's failure mattered most is exactly the kind of judgement the structured essays reward. Sources on Munich and on Hitler's actions are common in the source-based case study.

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Causes of the Second World War: the failure of the League of Nations, Hitler's foreign policy and appeasement for N(A)-Level Humanities (History elective)

A module overview of the causes of the Second World War in Europe for Singapore N(A)-Level Humanities (History elective). Why the League of Nations failed to stop aggression, how Hitler's foreign policy and step-by-step expansion broke the peace, and why the policy of appeasement gave way to war over Poland in 1939.

Generated by Claude Opus 4.85 min readSEAB-2126Updated 2026-06-13

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

Why this module matters
The failure of the League of Nations
Hitler's foreign policy and expansion
Appeasement and the outbreak of war
Check your knowledge

Why this module matters

The Second World War was the deadliest conflict in history, and N(A)-Level Humanities (History elective) asks you to explain why it broke out in Europe. This module matters because it pulls together earlier modules: the resentment created by the Treaty of Versailles, the rise of Hitler, and the weakness of the international system all feed into the war. The skill is to weigh these causes against each other and reach a judgement.

This guide ties together the module's dot points, each with its own worked detail and practice. See the subject hub at /sg-n-level/history and the full syllabus list at /sg-n-level/history/syllabus.

The failure of the League of Nations

The League of Nations was meant to keep the peace, but in the 1930s it failed. It had no army, important powers were absent, its sanctions were weak, and the Great Depression made countries selfish. When Japan invaded Manchuria and Italy invaded Abyssinia, the League could not stop them, which exposed its weakness and encouraged Hitler. Work through the detail at the failure of the League of Nations.

Hitler's foreign policy and expansion

Hitler aimed to overturn the Treaty of Versailles, rearm Germany and expand its territory. Step by step he rebuilt the army, remilitarised the Rhineland, united with Austria, and took the Sudetenland and then the rest of Czechoslovakia. Each unopposed move made him bolder. See Hitler's foreign policy and expansion.

Appeasement and the outbreak of war

Britain and France responded with appeasement, giving in to some demands to avoid war, with Munich in 1938 the high point. But when Hitler broke his promises and seized the rest of Czechoslovakia, appeasement collapsed, and the invasion of Poland in 1939 brought war. Study appeasement and the outbreak of war.

Building a structured essay on the causes of the war

A common structured-essay question is: "Appeasement was the main reason war broke out in 1939. How far do you agree?" Here is how to plan and write the judgement.

step 1: Decode the question and take a position

Underline the named factor (appeasement) and the command "how far". You must weigh it against the other causes (Hitler's aims, the League's failure, Versailles). Plan a clear stance, for example: appeasement allowed Hitler to grow stronger, but it was Hitler's own aggression that drove events, so the two cannot be separated.

step 2: Argue for the stated factor

Explain how appeasement helped cause the war. By giving in at Munich and earlier, Britain and France let Hitler rearm and expand without resistance, making him stronger and more confident, and convincing him the West would not fight. Support this with specific detail.

step 3: Weigh the other factors

Show that other causes also mattered. Hitler's foreign policy aimed at expansion from the start; the League's failure removed any check on aggression; and the resentment over Versailles gave Hitler his grievances and support. This balancing is where the marks are.

step 4: Reach a justified judgement

Decide and explain. A strong conclusion might argue that appeasement made war more likely by emboldening Hitler, but the driving force was Hitler's own ambition, so appeasement was a serious mistake rather than the main cause. The mark comes from the reasoned decision, not from summarising.

Check your knowledge

Try these under timed conditions, then test yourself with the module quiz.

State two reasons the League of Nations failed to keep the peace. (2 marks)
Explain how Hitler expanded German territory step by step before 1939. (4 marks)
State what is meant by the policy of appeasement. (2 marks)
Explain why Britain and France followed appeasement in the 1930s. (3 marks)
Explain why the invasion of Poland led to war in 1939. (3 marks)

Sources & how we know this

Singapore-Cambridge GCE Normal (Academic) Level Humanities (Social Studies, History) Syllabus 2126 — Singapore Examinations and Assessment Board (2026)