Causes of
World War I

Explore the long-term tensions and immediate triggers that plunged Europe into the deadliest conflict the world had ever seen by 1914.

AP World History

Europe: The Powder Keg

By the early 1900s, Europe was a web of rival empires, secret alliances, and nationalist movements. Decades of tension had turned the continent into a powder keg: all it needed was a single spark.

The M.A.I.N. Causes

Historians use the acronym M.A.I.N. to organize the four deep, structural causes that made war likely long before the first shot was fired.

Militarism

Arms races and glorification of military power

Alliances

Secret pacts that bound nations to defend each other

Imperialism

Competition for colonies and global dominance

Nationalism

Intense loyalty to one's nation or ethnic group

Militarism: The Arms Race

European nations poured resources into building massive armies and navies. Germany and Britain engaged in a fierce naval arms race, each trying to outbuild the other in dreadnought battleships.

Alliances: A Web of Pacts

By 1914, Europe was divided into two rival alliance blocs. A conflict between any two nations could drag in all the others, turning a local dispute into a continental war.

Imperialism: Colonial Rivalries

European powers competed fiercely for colonies in Africa and Asia. These rivalries created deep resentments and near-war crises well before 1914.

Scramble for Africa

By 1914, nearly all of Africa was under European control. Germany, a latecomer, resented Britain and France's vast empires.

Moroccan Crises

In 1905 and 1911, Germany challenged French influence in Morocco, nearly sparking war and deepening Franco-German hostility.

Nationalism: Pride and Tension

Nationalism took two powerful forms in pre-war Europe, both driving the continent toward conflict.

Great Power Nationalism

Major nations believed in their own superiority. France sought revenge for its 1871 defeat by Germany. Germany wanted a "place in the sun."

Ethnic Nationalism

Slavic peoples in Austria-Hungary and the Ottoman Empire demanded self-determination. Serbia became a center of Pan-Slavic ambition, backed by Russia.

How Alliances Created a Chain Reaction

Long-term vs Immediate Causes

AP essays require you to distinguish between causes that built up over decades and the specific trigger events of summer 1914.

	Long-term Causes	Immediate Causes
Timeframe	1870s - 1914	June - August 1914
Nature	Structural tensions	Specific events
Examples	Alliances, arms races, colonial rivalry	Assassination, ultimatums, mobilization
Effect	Made war likely	Made war happen

The Spark: Sarajevo, 1914

On June 28, 1914, Archduke Franz Ferdinand of Austria-Hungary was assassinated in Sarajevo by Gavrilo Princip, a Bosnian Serb nationalist linked to the Black Hand secret society.

1

Austria-Hungary blamed Serbia for harboring the assassins and issued a harsh ultimatum with impossible demands.

2

Serbia rejected key demands. Austria-Hungary declared war on July 28, exactly one month later.

3

Russia mobilized to defend its Slavic ally Serbia, triggering Germany's war plans against Russia and France.

4

Germany invaded Belgium to attack France (Schlieffen Plan), bringing Britain into the war by August 4.

How to Analyze Causes on the AP Exam

1

Identify the category: Is the cause related to Militarism, Alliances, Imperialism, or Nationalism?

2

Classify the timeframe: Is it a long-term structural factor or an immediate trigger event?

3

Explain the causal mechanism: How specifically did this factor make war more likely? Use evidence.

4

Connect to other causes: Show how factors reinforced each other (e.g., nationalism fueled the arms race).

5

Evaluate relative importance: Which cause was most significant? Defend your argument with specific evidence.

Example: The Balkan Crises

Prompt: How did events in the Balkans illustrate the interaction between nationalism and the alliance system?

1

Category: Nationalism + Alliances

2

Evidence: Serbia's Pan-Slavic nationalism threatened Austria-Hungary's multi-ethnic empire. Russia supported Serbia as a fellow Slavic state.

3

Mechanism: When Austria-Hungary moved against Serbia, Russia's alliance obligations and Slavic solidarity forced it to mobilize, which triggered Germany's alliance with Austria-Hungary.

4

Conclusion: Nationalism created the local crisis; the alliance system transformed it into a general European war.

Example: The Anglo-German Naval Race

Prompt: Explain how the naval arms race between Britain and Germany contributed to the outbreak of war.

Example: The Schlieffen Plan

Prompt: How did Germany's military planning make a wider war inevitable once any mobilization began?

Common Mistakes to Avoid

✕ Single-cause answers

Saying "the assassination caused WWI" ignores decades of structural tensions. The assassination was the trigger, not the cause.

✕ Blaming one country

Claiming Germany (or any single nation) was solely responsible oversimplifies a complex web of shared responsibility.

✕ Confusing types of nationalism

Great-power nationalism (French revanchism) and ethnic nationalism (Pan-Slavism) are distinct forces. Don't conflate them.

Timeline: Road to War

1871

German Unification

Germany defeats France, takes Alsace-Lorraine. France vows revenge.

1882

Triple Alliance Formed

Germany, Austria-Hungary, and Italy formalize their defensive pact.

1898

German Naval Laws

Germany begins building a massive fleet, alarming Britain.

1907

Triple Entente Formed

Britain, France, and Russia align against the Central Powers.

1912

Balkan Wars

Serbia expands, Austria-Hungary feels threatened, tensions spike.

1914

Assassination and War

Franz Ferdinand killed June 28. By August 4, all major powers at war.

Question 1 of 5

Which acronym do historians commonly use to describe the four long-term causes of World War I?

M.A.I.N. stands for Militarism, Alliances, Imperialism, and Nationalism: the four structural forces that made war likely long before 1914.

Question 2 of 5

The assassination of Archduke Franz Ferdinand is best described as:

The assassination was the immediate trigger, not the fundamental cause. The long-term causes (M.A.I.N.) created the conditions; the assassination ignited them by activating the alliance chain reaction.

Question 3 of 5

Historian A: "The alliance system was the primary cause of World War I. Without binding military commitments, the assassination of Franz Ferdinand would have remained a localized conflict between Austria-Hungary and Serbia."

Historian B: "The alliance system merely formalized existing rivalries. Even without formal treaties, the great powers would have been drawn into war by their competing imperial ambitions and nationalist ideologies."

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The point at issue between Historian A and Historian B is whether:

Historian A argues alliances were the primary independent cause. Historian B argues alliances merely reflected deeper forces (imperialism, nationalism) that would have led to war regardless. The debate is about whether alliances were a cause or an effect of rivalry.

Question 4 of 5

Why did Germany's Schlieffen Plan make a limited war impossible once Russia mobilized?

The Schlieffen Plan required immediately invading France through Belgium in any war with Russia, because Germany needed to defeat France quickly before turning east. This meant Russian mobilization = war with France and Belgium, bringing Britain in to defend Belgian neutrality.

Question 5 of 5

Which of the following best illustrates the role of nationalism in causing World War I?

The assassination was directly motivated by Pan-Slavic nationalism: the belief that all South Slavic peoples should be united under Serbian leadership, free from Austro-Hungarian rule. Option A is militarism, B is imperialism, and D is the alliance system.

Causes ofWorld War I

Europe: The Powder Keg

The M.A.I.N. Causes

Militarism: The Arms Race

Alliances: A Web of Pacts

Imperialism: Colonial Rivalries

Nationalism: Pride and Tension

How Alliances Created a Chain Reaction

Long-term vs Immediate Causes

The Spark: Sarajevo, 1914

How to Analyze Causes on the AP Exam

Example: The Balkan Crises

Example: The Anglo-German Naval Race

Example: The Schlieffen Plan

Common Mistakes to Avoid

Timeline: Road to War

Question 1 of 5

Question 2 of 5

Question 3 of 5

Question 4 of 5

Question 5 of 5

Causes of
World War I