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

The main causes were Hitler's aggressive foreign policy, which aimed to overturn the Treaty of Versailles, unite German-speakers and gain living space; the failure of the League of Nations to stop aggression in the 1930s, shown over Manchuria and Abyssinia; the policy of appeasement by Britain and France, which let Hitler get away with each move; and the events of 1939, especially the Nazi-Soviet Pact and the invasion of Poland, which finally brought British and French declarations of war. A strong answer shows how these factors combined rather than treating them separately.

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

Appeasement meant giving in to Hitler's demands in the hope of avoiding war, most famously at the Munich Agreement of 1938, when Britain and France let Germany take the Sudetenland. They followed it for several reasons: memories of the horrors of the First World War made them desperate to avoid another; they were militarily unprepared; some thought the Treaty of Versailles had been unfair so Hitler's demands seemed reasonable; and many saw Nazi Germany as a barrier against communism. Whether it made war more or less likely is a classic exam debate.

Did appeasement cause the Second World War?

It is one cause among several, and the exam wants a balanced judgement. Critics argue appeasement encouraged Hitler by showing he could break agreements without consequences, so each success made him bolder until war became unavoidable. Defenders argue Britain and France were buying time to rearm and that Hitler's aggression was the real cause. The strongest answers weigh appeasement against Hitler's ambitions and the League's failure, and decide how far appeasement was to blame rather than blaming it alone.

How did the events of 1939 lead to war?

After taking the Sudetenland in 1938, Hitler seized the rest of Czechoslovakia in March 1939, which showed his promises were worthless and ended appeasement. Britain and France then guaranteed Poland's independence. The Nazi-Soviet Pact of August 1939 freed Hitler to attack Poland without fear of a war on two fronts. When Germany invaded Poland on 1 September 1939, Britain and France honoured their guarantee and declared war, beginning the Second World War in Europe.

Why did the League of Nations fail to stop aggression in the 1930s?

The League failed because it lacked the power and will to enforce its decisions. It had no army, the major powers were absent or unwilling to act, and the Depression made states put self-interest first. The Manchurian Crisis (1931) and the Abyssinian Crisis (1935) showed that aggressors could defy the League without real punishment, since sanctions were weak and Britain and France would not risk war. These failures encouraged Hitler to believe he too could act with impunity.

SingaporeHistory

Causes of World War Two: Hitler's foreign policy, the failure of the League, appeasement and the outbreak of war in 1939 for O-Level Elective History

A module overview of the causes of the Second World War in Europe for Singapore O-Level Elective History. Hitler's aggressive foreign policy in the 1930s, the failure of the League of Nations to stop aggression, the policy of appeasement and the Munich Agreement, and how the events of 1939 led to the outbreak of war.

Generated by Claude Opus 4.86 min readSEAB-2174Updated 2026-06-13

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

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Why this module matters
Hitler's aggression and the League's failure
Appeasement and the road to war
Judging who was most to blame
Check your knowledge

Why this module matters

How the Second World War broke out in Europe is one of the most heavily examined topics in O-Level Elective History. The key developments leading to war are examinable as a source-based case study, and "how far do you agree" essays repeatedly ask whether appeasement, Hitler's policy or the League's failure was most to blame. The skill the module trains is weighing several causes against one another and reaching a justified judgement about responsibility.

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

Hitler's aggression and the League's failure

Two long-running causes set the scene for war.

Hitler's foreign policy and expansion. Hitler aimed to overturn Versailles, unite German-speakers and win living space, and he acted through rearmament, the Rhineland, the Anschluss with Austria and the Sudetenland. Study Hitler's foreign policy and expansion.
The failure of the League of Nations. Over Manchuria and Abyssinia the League showed it could not stop aggressors, weakened by the Depression, the absence of major powers and the self-interest of Britain and France. See the failure of the League of Nations.

Appeasement and the road to war

Two further dot points carry the story to its outbreak.

The policy of appeasement. Why Britain and France gave way to Hitler, the Munich Agreement over the Sudetenland in 1938, and the arguments for and against the policy. Work through the policy of appeasement.
The outbreak of war in Europe in 1939. The seizure of the rest of Czechoslovakia, the British guarantee to Poland, the Nazi-Soviet Pact, the invasion of Poland and the declaration of war. See the outbreak of war in Europe 1939.

Judging who was most to blame

The set-piece essay asks "how far" appeasement, or Hitler, or the League's failure caused the war. The strongest answers argue that the causes interacted: Hitler provided the ambition and aggression, the League's failure showed aggressors went unpunished, and appeasement confirmed that Britain and France would not act, so each made the next step easier. You should weigh the named factor against the others and decide how far it was responsible.

Answering "How far was appeasement to blame for the war?"

Take: "The policy of appeasement was the main reason war broke out in Europe in 1939. How far do you agree?"

step 1: Read the question and plan a stance

The named factor is appeasement; "how far" asks you to weigh it against the other causes and decide. Plan a position, for example: appeasement made war more likely by emboldening Hitler, but Hitler's aggression was the underlying cause, so appeasement was a contributing rather than the main reason.

step 2: Argue for appeasement as a cause

Explain how appeasement helped cause war: by giving way at Munich and elsewhere, Britain and France showed Hitler he could break agreements without consequences, so each success made him bolder and convinced him the West would not fight, encouraging the gamble over Poland.

step 3: Weigh the other causes

Show appeasement was not the only cause. Hitler's ambition and aggression were the driving force; the League's failure over Manchuria and Abyssinia had already shown aggressors went unpunished; and the events of 1939, the seizure of Czechoslovakia and the Nazi-Soviet Pact, were decisive final steps. Consider too that appeasement may have bought time to rearm.

step 4: Decide and justify

Reach a judgement. A strong answer might argue that appeasement made war more likely by encouraging Hitler, but it was Hitler's determination to expand that made war inevitable, so appeasement was an important contributing cause rather than the main one. The mark lies in the reasoned decision.

Check your knowledge

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

State two aims of Hitler's foreign policy. (2 marks)
Explain why the League of Nations failed to stop aggression in the 1930s. (3 marks)
State what was agreed at the Munich Agreement of 1938. (2 marks)
Explain two reasons why Britain and France followed appeasement. (4 marks)
Explain how the events of 1939 led to the outbreak of war. (3 marks)

Sources & how we know this

Singapore-Cambridge GCE O-Level Humanities (Elective History) Syllabus 2174 — Singapore Examinations and Assessment Board (2026)