7.6 Causes of World War II

World War II grew out of problems left over from World War I plus new pressures that broke the global order. The main causes were the unstable peace settlement after World War I, the Great Depression, continued imperialist ambitions, and especially the rise of fascist and totalitarian regimes, above all the aggressive militarism of Nazi Germany under Adolf Hitler.

Causes of WW2 in AP World

AP World History 7.6 names four main causes of World War II: the unsustainable peace settlement after World War I, the global economic crisis caused by the Great Depression, continued imperialist aspirations, and the rise of fascist and totalitarian regimes.

The most important cause to emphasize is the aggressive militarism of Nazi Germany under Adolf Hitler, but strong answers do not stop there. Connect Germany's expansion to wider patterns: economic instability weakened democracies, imperial ambitions continued in Europe and Asia, and the post-World War I order failed to keep the peace.

Why This Matters for the AP World History Exam

This topic asks you to explain the causes and consequences of World War II, so it is built around causation, one of the core reasoning skills on the AP World History exam. You should be able to connect long-term causes (the peace settlement after World War I) to medium-term causes (economic collapse) and short-term triggers (acts of aggression in the late 1930s).

Causation questions reward you for ranking and linking causes, not just listing them. You can also use this topic for continuity and change over time by comparing the causes of World War I and World War II, since some forces like militarism, nationalism, and imperialism carried over while others like the Great Depression and fascism were new.

Key Takeaways

• The four big causes to know are the unsustainable post-World War I peace settlement, the Great Depression, continued imperialist aspirations, and the rise of fascist and totalitarian regimes.
• The rise of aggressive militarism in Nazi Germany under Adolf Hitler is the cause the AP framework highlights most strongly.
• Economic crisis from the Great Depression weakened democracies and pushed desperate populations toward extremist parties.
• Imperialist expansion continued in the 1930s, including aggression by Germany, Italy, and Japan.
• The war began with a slow build-up of tensions rather than a single spark, ending with Germany's invasion of Poland in 1939.

The Four Core Causes

The AP framework groups the causes of World War II into four main forces. Keep these as your anchor and hang specific examples on them.

Unsustainable Peace After World War I

The peace settlement that ended World War I left deep resentment, especially in Germany. As an example of how this played out, the Treaty of Versailles assigned war blame to Germany, demanded heavy reparations, stripped Germany of territory and overseas colonies, and sharply limited its military. That anger gave nationalist and extremist leaders something to exploit. Italy also felt shortchanged by its limited gains, which fed Mussolini's calls for national revival.

Global Economic Crisis (Great Depression)

The Great Depression after 1929 spread instability worldwide.

• Countries already burdened by reparations, like Germany and Austria, were hit hard.
• When American loans to Germany dried up, the damage rippled across European economies.
• High unemployment and inflation destabilized democratic governments and made extremist parties promising order and recovery more appealing.

Continued Imperialist Aspirations

Even after World War I, major powers kept pursuing territorial gains. This expansionism is one of the causes the AP framework names directly. The aggressive moves of the 1930s by Germany, Italy, and Japan all reflect this drive for territory, resources, and markets.

Rise of Fascist and Totalitarian Regimes

This is the cause the AP framework emphasizes most. As democratic systems faltered, authoritarian regimes promised national strength and restored pride. The clearest case is Nazi Germany under Adolf Hitler, whose aggressive militarism is singled out as a central cause of the war.

How the Causes Played Out

The following examples are illustrations of the four core causes, not a separate required list. Use them as evidence when you write about causation.

Germany under Adolf Hitler

• Nazi ideology stressed racial hierarchy, anti-Semitism, and anti-communism.
• The regime used propaganda through film, rallies, newspapers, and schools to shape public opinion.
• Hitler rebuilt the military in violation of the postwar limits and reintroduced conscription.
• He moved step by step: remilitarizing the Rhineland in 1936, the Anschluss with Austria in 1938, annexing the Sudetenland in 1938, and invading Poland in 1939.

Italy under Benito Mussolini

• Fascism called for national unity, glorification of the state, and suppression of dissent.
• Mussolini invaded Ethiopia in 1935 to build what he framed as a new Roman empire.
• His government organized the economy around state-controlled corporations rather than free-market competition.

Japan's Militarist Expansion

• Japan invaded Manchuria in 1931 and renamed it Manchukuo.
• It launched full-scale war with China in 1937.
• It justified military expansion through the Greater East Asia Co-Prosperity Sphere, which functioned as cover for imperial control.

Aggression and Response Table

This table shows how aggressive actions met weak responses, which helped the conflict escalate.

Appeasement and the Road to War

Appeasement is a useful example of why aggression went unchecked, though it is an application of the broader causes rather than a separate required cause.

• Britain and France hoped that giving in to some of Hitler's demands would prevent another war.
• The Munich Agreement in 1938 let Hitler take the Sudetenland in return for a promise of no further expansion.
• Hitler broke that promise by seizing the rest of Czechoslovakia in 1939, then invaded Poland on September 1, 1939.
• Britain and France had drawn the line at Poland and declared war on Germany, beginning World War II.

How to Use This on the AP World History Exam

Free Response

When a prompt asks about the causes of World War II, organize your answer around the four core causes rather than a flat list of events. Lead with the rise of fascist and totalitarian regimes, especially Nazi Germany, since that is the cause the framework stresses most, then connect it to the peace settlement, the economic crisis, and continued imperialism.

For a strong causal argument, link causes together. For example, show how the Great Depression weakened democracies, which opened the door for extremist regimes, which then pursued aggressive expansion. Use specific evidence like the remilitarization of the Rhineland or the invasion of Manchuria to support each claim.

Comparison and Change Over Time

This topic pairs well with the causes of World War I. Be ready to explain what carried over (nationalism, militarism, imperialist competition) and what was new (the Great Depression and the rise of fascism). That contrast is exactly the kind of continuity and change reasoning the exam rewards.

Common Trap

Do not reduce the war to "Versailles was too harsh" or "one person caused it." The framework expects you to weigh several causes and explain their relative significance, not lean on a single explanation.

Common Misconceptions

• World War II did not begin with a single trigger like the assassination that helped start World War I. It built up slowly through the 1930s before the invasion of Poland in 1939.
• The Treaty of Versailles was a major source of resentment, but it was not the only cause. Treating it as the sole cause ignores the Great Depression, imperialism, and the rise of fascist regimes.
• Appeasement was a response to aggression, not a root cause of the war. The deeper causes were the unstable peace, economic crisis, imperialist ambitions, and totalitarian regimes.
• Fascism and totalitarianism were not limited to Germany. Italy and Japan also pursued aggressive, expansionist policies, though Nazi Germany's militarism is the case the framework highlights most.
• Reparations numbers and exact military caps are background detail, not the point. The exam cares more about how resentment and economic strain fed extremism than about memorizing figures.

Related AP World History Guides

• Unit 7 Overview: Global Conflict
• 7.1 Shifting Power After 1900
• 7.2 Causes of World War I
• 7.4 Economy in the Interwar Period
• 7.5 Unresolved Tensions After World War I
• 7.3 Conducting World War I