Explore how events between 1900 and 1945 continue to shape today's world.

Essential Events Between 1900 and 1945

Learn how two world wars and other critical developments reshaped global affairs in the first half of the twentieth century.

Timeline timeline

How Do Countries Decide Whether to Go to War?

Learn how balances and imbalances of power contributed to World Wars I and II.

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Why Did World War I Happen?

In this free resource on World War I, explore the causes and effects of the Great War to understand how the conflict shaped world history.

Infographic infographic

Why Did World War II Happen?

In this free resource on World War II, understand the causes of World War II and why these issues drove countries back to battle just two decades after World War I.

Infographic infographic

What Is Fascism?

In this free resource, learn how Benito Mussolini and Adolf Hitler rose to power and the lessons their political journeys hold for today.

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How Did the United States Become a Global Power?

Learn about the three wars that transformed the United States’ standing in the world.

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What Are the Origins of Communism?

Explore the different ways Marx, Lenin, and Stalin interpreted communism and dive into the history of translating an ideology into policy.

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World at War Module Assessment

Questions to check your understanding.

Interactive interactive