7.2 Causes of World War I

World War I broke out in 1914 because imperialist competition for resources, a tangled alliance system, intense nationalism, and growing militarism turned regional tensions into a global conflict. The assassination of Archduke Franz Ferdinand in Sarajevo was the spark, but the underlying causes had built up over decades.

Causes of WW1 in AP World History

For AP World 7.2, the main causes of World War I were imperialist expansion and competition for resources, territorial and regional conflicts, a flawed alliance system, and intense nationalism. Militarism is also a useful supporting category because European states expanded military planning and spending before 1914.

The exam move is causation: separate long-term causes from the short-term trigger. The assassination of Archduke Franz Ferdinand started the July Crisis, but the deeper causes explain why that regional crisis expanded into a global conflict.

Why This Matters for the AP World History Exam

This topic is about causation, one of the core historical thinking skills in AP World History. You need to explain how long-term structural causes (imperial rivalries, alliances, nationalism, militarism) combined with a short-term trigger (the assassination) to produce a global war.

That kind of thinking shows up on both multiple-choice questions tied to documents and on free-response questions that ask you to analyze causes and connect them to broader processes. Being able to separate underlying causes from the immediate spark, and to weigh which causes mattered most, is exactly the analysis this unit rewards.

Key Takeaways

• The main causes of World War I were imperialist expansion and competition for resources, territorial and regional conflicts, a flawed alliance system, and intense nationalism.
• The MAIN acronym (Militarism, Alliances, Imperialism, Nationalism) is a study tool for organizing those causes, not official AP terminology.
• The assassination of Archduke Franz Ferdinand in Sarajevo (June 28, 1914) was the immediate trigger, not the underlying cause.
• The alliance system turned a regional dispute between Austria-Hungary and Serbia into a war involving every major European power.
• Imperialism helped globalize the conflict by drawing colonies and territories across Africa, the Middle East, and Asia into the fighting.
• Practice distinguishing long-term structural causes from the short-term spark, since that distinction is central to causation questions.

The MAIN Causes of World War I

The causes of World War I built up over decades through imperial competition, rival alliances, rising nationalism, and an arms race. MAIN is a memory tool that groups these into four categories.

Militarism

Militarism is the belief that a strong military is central to national success. Industrialization let European powers expand military spending and build new weapons like machine guns, heavy artillery, and chemical weapons.

• Germany and Britain competed in a naval arms race to build advanced battleships called dreadnoughts.
• Conscription, or mandatory military service, became widespread.
• Military leaders gained more influence over government decisions.
• Germany's Schlieffen Plan showed that major powers were already drawing up blueprints for war.

By 1914, most European states had large arsenals and were prepared for large-scale conflict.

Alliances

Alliances were meant to provide protection, but they created a domino effect. When one nation went to war, its allies were pulled in too.

Italy initially aligned with the Central Powers but switched sides in 1915. The Ottoman Empire later joined the Central Powers. Because of these commitments, a conflict between two countries could rapidly expand to involve all the major powers, which is what happened after Austria-Hungary declared war on Serbia.

Imperialism

Imperialism is the drive to expand national power by acquiring territory. As European powers competed for colonies in Africa and Asia, tensions grew.

• Germany, a newer imperial power, challenged British and French control.
• Rivalries intensified in places like Morocco, where German involvement triggered crises.
• Colonial disputes fed nationalism and militarism.

Imperialism did not directly start the war, but it globalized it by drawing colonies and distant territories into the fighting.

Nationalism

Nationalism is strong pride in one's nation or ethnic group. It could both unify and divide states.

• In Austria-Hungary and the Ottoman Empire, nationalism among ethnic minorities created internal instability.
• In Serbia, Pan-Slavic nationalism pushed for a larger Slavic state, with support from Russia.
• Nationalism encouraged the idea that war was honorable and that one's nation was superior.

Nationalism helped justify aggression, especially when framed as national superiority or self-determination.

The Immediate Cause: Assassination of Archduke Franz Ferdinand

On June 28, 1914, Archduke Franz Ferdinand of Austria-Hungary and his wife were assassinated in Sarajevo by Gavrilo Princip, a Bosnian Serb nationalist linked to a secret society known as the Black Hand. The group wanted a unified Slavic state free from Austro-Hungarian control.

Austria-Hungary blamed Serbia and, with German backing, issued a list of demands. Serbia's partial rejection led Austria-Hungary to declare war. The alliance system then escalated the conflict quickly:

1. Russia mobilized to protect Serbia.
2. Germany declared war on Russia.
3. Germany invaded Belgium to attack France.
4. Britain declared war on Germany for violating Belgian neutrality.

Within weeks, a local dispute became a continental and then a world war.

Major Participants by 1917

Fighting took place not only in Europe but also in Africa, the Middle East, and Asia, which is part of why this counts as the first truly global war of the 20th century.

How to Use This on the AP World History Exam

Free Response

When a prompt asks about the causes of World War I, separate the long-term causes (imperial competition, alliances, nationalism, militarism) from the short-term trigger (the assassination). A strong response does not just list causes; it explains how they connected and reinforced one another.

If a question asks you to evaluate the relative significance of causes, take a clear position. For example, you might argue that the alliance system mattered most because it turned a regional dispute into a global war, then support that with specific evidence.

Using Sources Effectively

For multiple-choice and document-based work, watch for sources that reveal militaristic attitudes, nationalist pride, or imperial rivalry. Ask what the source suggests about why Europeans expected or accepted war, and use the source's point of view to support claims about causes.

Common Trap

Do not treat the assassination as the real reason for the war. On causation questions, the assassination is the spark. The deeper causes are the structural tensions that had been building for decades.

Common Misconceptions

• The assassination of Franz Ferdinand caused World War I on its own. It was the immediate trigger, but the underlying causes were long-term imperial, alliance, nationalist, and military tensions.
• MAIN is official AP content. MAIN is a helpful memory device for organizing causes, not required AP terminology. Focus on explaining the causes, not just naming the acronym.
• Alliances prevented war. They were meant to provide protection, but in 1914 they pulled more countries into the conflict and helped it expand.
• The war was fought only in Europe. Imperial connections spread the fighting to Africa, the Middle East, and Asia, making it a global conflict.
• Italy fought with Germany and Austria-Hungary the whole war. Italy started in the Triple Alliance but switched to the Allied side in 1915.

ze several major causes.

Was the assassination the main cause of World War I?

No. The assassination of Archduke Franz Ferdinand was the immediate trigger. The deeper causes were long-term tensions from imperialism, alliances, nationalism, militarism, and regional conflicts.

How did alliances help cause World War I?

Alliances helped expand the conflict because states were committed to supporting one another. A regional dispute involving Austria-Hungary and Serbia quickly pulled in Russia, Germany, France, and Britain.

How did imperialism contribute to World War I?

Imperialism increased competition among European powers for colonies, resources, and global influence. Those rivalries raised tensions before 1914 and helped make the war global.

How should I write about the causes of WW1 on AP World FRQs?

Separate long-term causes from the immediate trigger, then explain how the causes connected. A strong answer might argue that alliances mattered most because they turned a regional conflict into a broader war.

Related AP World History Guides

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