What you'll learn
This revision guide covers the key causes of the Second World War, from the Treaty of Versailles in 1919 to the outbreak of war in September 1939. You'll examine how Hitler's foreign policy, the weaknesses of the League of Nations, and the policy of appeasement contributed to global conflict. Understanding both long-term resentments and short-term crises is essential for CIE IGCSE examination success.
Key terms and definitions
Treaty of Versailles — The 1919 peace settlement that ended the First World War, imposing harsh territorial, military and financial penalties on Germany
Appeasement — The British and French policy of giving in to Hitler's demands in the 1930s to avoid war, most associated with Prime Minister Neville Chamberlain
Lebensraum — German term meaning "living space"; Hitler's justification for expanding eastwards into Poland and the Soviet Union to provide land for the German population
Anschluss — The union of Germany and Austria, forbidden by the Treaty of Versailles but achieved by Hitler in March 1938
Sudetenland — The German-speaking border areas of Czechoslovakia that Hitler demanded and received at the Munich Conference in September 1938
Munich Agreement — The September 1938 settlement in which Britain and France allowed Germany to annex the Sudetenland in return for Hitler's promise of no further territorial demands
Remilitarisation — Hitler's reintroduction of conscription and reoccupation of the Rhineland, violating the Treaty of Versailles
Nazi-Soviet Pact — The August 1939 non-aggression agreement between Hitler and Stalin that included secret protocols to divide Poland and gave Hitler confidence to invade
Core concepts
The Treaty of Versailles and German resentment
The Treaty of Versailles created deep resentment in Germany that Hitler exploited effectively. The treaty's main terms included:
Territorial losses: Germany lost 13% of its European territory, including Alsace-Lorraine to France, the Polish Corridor to Poland, and all overseas colonies. The loss of the Polish Corridor was particularly humiliating as it separated East Prussia from the rest of Germany.
Military restrictions: Germany's army was limited to 100,000 men, conscription was banned, and Germany could possess no tanks, submarines or military aircraft. The Rhineland was demilitarised, meaning no German troops could be stationed there.
War guilt and reparations: Article 231, the "war guilt clause," forced Germany to accept full responsibility for starting the war. Reparations were set at £6.6 billion in 1921, a sum Germany claimed would cripple its economy for generations.
League of Nations exclusion: Germany was initially excluded from the League of Nations, treating it as a pariah state rather than an equal partner in maintaining peace.
Many Germans viewed the treaty as a "Diktat" — a dictated peace imposed without negotiation. The Weimar Republic government that signed it became associated with national humiliation, which Hitler used to gain support by promising to overturn Versailles.
The weaknesses of the League of Nations
The League of Nations, established to maintain peace, proved unable to prevent aggressive expansion in the 1930s. Its failures encouraged Hitler's ambitions:
Structural weaknesses: The League lacked an army of its own and relied on member states to enforce decisions through economic sanctions. The United States never joined, and the Soviet Union was excluded until 1934, limiting the League's global authority. Unanimous decisions were required in the Council, making swift action difficult.
Failures in Manchuria (1931-33): When Japan invaded Manchuria, the League condemned the action but imposed no effective sanctions. Japan simply withdrew from the League in 1933, demonstrating that aggressors faced no real consequences.
Failures in Abyssinia (1935-36): Mussolini's Italy invaded Abyssinia (Ethiopia). The League imposed economic sanctions but excluded oil, the one commodity that might have stopped Italy's war machine. Britain and France secretly negotiated the Hoare-Laval Pact to give Mussolini most of Abyssinia, revealing their unwillingness to uphold League principles.
These failures taught Hitler that the League could not stop determined aggressors, and that Britain and France would prioritise their own interests over collective security.
Hitler's foreign policy aims and actions
Hitler's foreign policy combined ideological goals with opportunistic aggression. His main aims were clearly stated in Mein Kampf and his speeches:
Overturning Versailles: Hitler sought to reverse all territorial losses, end reparations, and rearm Germany. This resonated with most Germans regardless of their support for Nazism.
Uniting all German speakers: Hitler wanted to bring all ethnic Germans into a Greater Germany, including those in Austria, Czechoslovakia and Poland.
Lebensraum: Hitler planned to conquer territory in Eastern Europe and the Soviet Union, viewing Slavic peoples as racially inferior and destined for enslavement or extermination.
Key actions 1933-1939:
- 1933: Germany left the League of Nations and began secret rearmament
- 1934: Attempted Nazi coup in Austria failed; Mussolini prevented German intervention
- 1935: Saar plebiscite returned the region to Germany legally; conscription reintroduced openly
- 1936: Remilitarisation of the Rhineland in March violated both Versailles and the Locarno Treaties. Hitler gambled that Britain and France would not respond militarily — he was correct
- 1936-39: German and Italian intervention in the Spanish Civil War provided military testing grounds and drew Mussolini closer to Hitler (Rome-Berlin Axis, 1936)
- 1938 (March): Anschluss with Austria. German troops entered Austria unopposed; a rigged plebiscite showed 99% support
- 1938 (September): Sudetenland crisis and Munich Agreement. Hitler threatened war over Czechoslovakia; Chamberlain agreed to German annexation
- 1939 (March): Hitler broke the Munich Agreement by occupying the rest of Czechoslovakia, destroying appeasement's credibility
- 1939 (September): Invasion of Poland triggered declarations of war by Britain and France
The policy of appeasement
Appeasement dominated British and French foreign policy from 1936-1939, particularly under Neville Chamberlain (Prime Minister 1937-1940).
Reasons for appeasement:
- Memory of World War One: The slaughter of 1914-18 created a "never again" mentality. Politicians and publics desperately wanted to avoid another war
- Economic constraints: The Great Depression left Britain and France financially weakened; rearmament was expensive
- Moral doubts about Versailles: Many British politicians believed the Treaty of Versailles had been too harsh, making some of Hitler's demands seem reasonable
- Fear of communism: Some conservatives viewed Nazi Germany as a bulwark against Soviet expansion
- Military unpreparedness: British and French armed forces needed time to rearm, particularly air forces
- Imperial overstretch: Britain had global commitments and could not concentrate forces in Europe
Key moments of appeasement:
The Rhineland (1936): France wanted to respond militarily but Britain refused support. Hitler later admitted he would have withdrawn if opposed — a crucial missed opportunity.
Austria (1938): Britain and France accepted the Anschluss as inevitable, viewing Austrian Germans as having self-determination rights.
Munich (1938): Chamberlain met Hitler three times, eventually agreeing to German annexation of the Sudetenland. Chamberlain returned claiming "peace for our time." Czechoslovakia was not consulted about losing its territory.
The failure of appeasement:
Hitler's occupation of Czechoslovakia in March 1939 revealed that his ambitions went beyond uniting German speakers. When Hitler then demanded Danzig and the Polish Corridor, Britain and France issued guarantees to Poland, ending appeasement. However, this policy had already:
- Allowed Germany to rearm and become militarily powerful
- Destroyed collective security and weakened the League
- Driven Stalin to doubt Western willingness to oppose Hitler
- Given Hitler confidence that Britain and France lacked resolve
The Nazi-Soviet Pact and the outbreak of war
The Nazi-Soviet Pact of August 1939 shocked the world and made war almost inevitable.
Why Stalin signed:
Stalin distrusted Britain and France after Munich excluded the Soviet Union and handed Hitler Czech military resources. Britain and France conducted negotiations with Stalin half-heartedly in summer 1939, while Hitler offered concrete terms: a sphere of influence in Eastern Europe and half of Poland.
Why Hitler signed:
Hitler wanted to avoid a two-front war. The pact meant he could attack Poland without Soviet interference and without facing the situation Germany endured in 1914-18.
Terms and secret protocols:
Publicly, Germany and the USSR agreed not to attack each other for ten years. Secret protocols divided Eastern Europe into spheres of influence: eastern Poland, Finland, Estonia, Latvia and Bessarabia would go to the USSR; western Poland would go to Germany.
Invasion of Poland:
On 1 September 1939, Germany invaded Poland using Blitzkrieg tactics. Britain and France, bound by guarantees to Poland, issued ultimatums demanding German withdrawal. When Hitler ignored these, Britain declared war on 3 September, followed by France. The Second World War had begun.
The USSR invaded eastern Poland on 17 September, completing the partition agreed in the Nazi-Soviet Pact.
Long-term and short-term causes
Examiners expect you to distinguish between different types of causes:
Long-term causes (underlying factors):
- Resentment of the Treaty of Versailles
- Weaknesses of the League of Nations
- Economic instability after the Great Depression enabling extremism
- Unresolved territorial disputes in Europe
Medium-term causes:
- Hitler's rise to power (1933)
- Failure to stop remilitarisation (1936)
- Formation of the Rome-Berlin Axis
- Policy of appeasement encouraging aggression
Short-term causes (immediate triggers):
- Destruction of Czechoslovakia (March 1939) ending appeasement
- British and French guarantees to Poland (March 1939)
- Nazi-Soviet Pact (August 1939)
- German invasion of Poland (1 September 1939)
Worked examples
Example 1: Four-mark explanation question
Question: Describe the key features of the Treaty of Versailles. [4 marks]
Model answer:
One key feature was territorial losses. Germany lost 13% of its European territory, including the Polish Corridor to Poland and Alsace-Lorraine to France. [1 mark for feature + 1 mark for supporting detail]
Another key feature was military restrictions. Germany's army was limited to 100,000 men and it was forbidden from possessing tanks, submarines or military aircraft. [1 mark for feature + 1 mark for supporting detail]
Examiner note: This question requires two key features with supporting detail. Avoid simply listing terms — develop each point with specific examples.
Example 2: Six-mark causation question
Question: Why did Britain and France follow a policy of appeasement in the 1930s? [6 marks]
Model answer:
One reason was the memory of World War One. The terrible losses of 1914-18 created public opinion strongly opposed to another war. Politicians like Chamberlain believed avoiding war was essential, making them willing to compromise with Hitler's demands. [2 marks: reason + explanation]
Another reason was doubt about the fairness of Versailles. Many British politicians believed the Treaty had been too harsh on Germany. This made Hitler's early demands, such as the return of the Saar and German rearmament, seem morally reasonable. [2 marks: reason + explanation]
A further reason was military unpreparedness. Britain's armed forces, particularly the Royal Air Force, needed time to rearm after years of military cuts. Chamberlain believed appeasement would buy time for rearmament while avoiding immediate conflict. [2 marks: reason + explanation]
Examiner note: Provide three developed reasons. Each paragraph should explain why the factor led to appeasement, not just describe what happened.
Example 3: Ten-mark evaluation question
Question: "The Nazi-Soviet Pact was the main reason for the outbreak of war in 1939." How far do you agree? [10 marks]
Model answer structure:
Introduction: State your argument (e.g., "While the Nazi-Soviet Pact was crucial, it was the culmination of failures since 1919 rather than the sole cause.")
Paragraph 1 (agreeing): The Nazi-Soviet Pact made war immediate and inevitable. It freed Hitler from fear of a two-front war, giving him confidence to invade Poland. Stalin's agreement to divide Poland meant Germany could attack without Soviet opposition. The pact removed the final obstacle to Hitler's aggression, making it directly responsible for war breaking out in September 1939.
Paragraph 2 (agreeing): Without the pact, Hitler might have hesitated. Britain and France had guaranteed Poland, and Hitler feared fighting on two fronts as Germany had in World War One. The pact transformed the strategic situation, suggesting it was the decisive factor that triggered war.
Paragraph 3 (disagreeing): However, the underlying cause was Hitler's expansionist foreign policy. From Mein Kampf onwards, Hitler sought Lebensraum in Eastern Europe. The invasion of Poland would have happened eventually because Hitler's ideology demanded it. The pact was a tactical move, not the fundamental cause.
Paragraph 4 (disagreeing): Appeasement enabled Hitler's growing power. Britain and France's failure to stop remilitarisation in 1936 or prevent the Anschluss and Munich in 1938 allowed Germany to become strong enough to risk war. Had they acted earlier, Hitler might have been deterred or overthrown.
Conclusion: The Nazi-Soviet Pact was the immediate trigger, but war resulted from accumulated failures to stop Hitler since 1933 and unresolved resentments since 1919. The pact was necessary for war in September 1939, but underlying causes made conflict probable regardless.
Examiner note: Top-level answers show balanced analysis, examining both sides before reaching a supported judgement. Use phrases like "However" and "On the other hand" to show evaluation.
Common mistakes and how to avoid them
Confusing chronology: Students often muddle the order of Hitler's actions. Create a timeline from 1933-1939 to memorise the sequence: rearmament (1935), Rhineland (1936), Austria (March 1938), Sudetenland (September 1938), Czechoslovakia (March 1939), Poland (September 1939).
Treating appeasement as cowardice: Avoid moral judgements. Examiners want historical understanding of why politicians made decisions given their context — fear of another World War One, economic problems, and moral doubts about Versailles.
Ignoring Soviet perspectives: Many answers focus only on Britain, France and Germany. Remember Stalin's role: his exclusion from Munich, his distrust of the West, and his decision to sign the Nazi-Soviet Pact were crucial to war breaking out when and how it did.
Listing facts without explanation: In causation questions, don't just describe what happened. Explain why each factor contributed to war. Use connectives: "This led to..." or "As a consequence..."
One-sided answers to "How far" questions: These require balance. Even if you largely agree with the statement, acknowledge counter-arguments before explaining why your view is stronger. This demonstrates the evaluation skills examiners reward.
Forgetting the Treaty of Versailles: Every answer about the origins of World War Two should connect back to Versailles where relevant. The treaty's harsh terms created resentment Hitler exploited and made some Germans support his foreign policy aims.
Exam technique for "The 20th Century: International Relations since 1919 — The Origins of the Second World War"
Command word awareness: "Describe" requires factual detail (4 marks); "Why/Explain" requires causes with explanation (6 marks); "How far/How important" requires evaluation of different factors with a judgement (10 marks). Tailor your answer length and depth accordingly.
Use the mark scheme structure: Four-mark questions need two points with detail. Six-mark questions need three explained reasons. Ten-mark questions need balanced analysis across multiple paragraphs with an introduction and conclusion. Plan your answer structure before writing.
Deploy precise evidence: Use specific dates, names and terms. "Treaty of Versailles," "Article 231," "£6.6 billion reparations," "March 1936," "Neville Chamberlain" demonstrate detailed knowledge. Vague statements like "Germany was treated badly" score poorly.
Make judgements explicit: In evaluation questions, state your view clearly in the introduction and conclusion. Use phrases like "the most important factor was..." or "this was crucial because..." to signal analytical thinking rather than just describing events.
Quick revision summary
The Second World War resulted from multiple causes: the harsh Treaty of Versailles created German resentment; the League of Nations failed to stop aggression in Manchuria and Abyssinia; Hitler pursued Lebensraum and the reversal of Versailles through remilitarisation, Anschluss and the seizure of Czechoslovakia; Britain and France appeased Hitler due to memories of World War One, economic weakness and moral doubts about Versailles; the Nazi-Soviet Pact of August 1939 freed Hitler to invade Poland on 1 September 1939, triggering British and French declarations of war.