What caused the First World War?

Welcome to the Causes of World War I!

Hello! This chapter is one of the most important (and sometimes confusing!) topics in IGCSE History. We are exploring the crucial question: What caused the First World War?

Instead of thinking of it as one simple event, think of the outbreak of war in 1914 as a chain reaction. Many long-term pressures built up over decades, turning Europe into a "tinderbox." All it needed was a single spark.

These notes will help you break down those long-term pressures and the final short-term trigger. Don't worry if this seems tricky at first; we will use simple mnemonics to make sure you remember the key factors!

Section 1: The Long-Term Causes (The MAIN Factors)

Historians often group the long-term causes of the First World War into four easy-to-remember categories, known by the mnemonic MAIN:

• Militarism
• Alliance System
• Imperialism (Colonial Rivalries)
• Nationalism

1. Militarism and the Arms Race

Militarism means aggressively building up military strength and prioritizing military solutions.
The late 19th and early 20th centuries saw a massive arms race (a competition between nations to achieve military superiority), which significantly increased the likelihood of war.

• Army Growth: Powers like Germany, France, and Russia constantly increased the size of their armies. Russia had the largest army, but Germany had the best-trained and equipped forces.
• The Naval Race: The most famous competition was between Britain and Germany. Since Britain was an island, its naval power (the Royal Navy) was vital for defending its vast empire. When Germany began building large, powerful battleships called Dreadnoughts (first launched by Britain in 1906), Britain felt seriously threatened.
• War Planning: Governments spent huge amounts on arms, and generals made complex plans (like Germany’s Schlieffen Plan). These detailed plans often demanded rapid mobilization, meaning once a conflict started, it was difficult to stop.

Key Takeaway: Militarism created deep suspicion and gave military leaders enormous influence, making mobilization difficult to reverse.

2. The Alliance System and European Diplomacy

The Alliance System divided Europe into two rigid, armed camps. This system was meant to keep peace by creating a balance of power, but it had the opposite effect: if two countries fought, their allies were dragged in, turning a small conflict into a European war.

The Two Major Blocs:

1. The Triple Alliance (Central Powers):

• Germany
• Austria-Hungary (A-H)
• Italy (Though Italy would abandon the alliance in 1915)

2. The Triple Entente (Allied Powers):

• France
• Russia
• Britain

Analogy: Imagine two teams playing football. If a player from Team A tackles a player from Team B, the whole of Team A rushes to help their player, and the whole of Team B rushes to help theirs. The alliance system ensured that any quarrel between two states became a quarrel involving all six Great Powers.

Did you know? The syllabus also mentions the 1902 Anglo-Japanese Alliance. This was a non-European agreement that allowed Britain to protect its interests in Asia, showing that the alliance web extended globally, though it wasn't a direct cause of the war in Europe.

3. Imperialism and Colonial Rivalries

Imperialism refers to the struggle between Great Powers to gain overseas colonies and build vast global empires in the 19th century.

• Economic Competition: Great Powers competed fiercely for raw materials, markets, and trade routes globally.
• Germany's Ambition: After Germany unified in 1871, Kaiser Wilhelm II pursued Weltpolitik (World Policy), aiming to turn Germany into a global colonial power. This directly challenged the established empires of Britain and France.
• Moroccan Crises: Tensions erupted in Morocco, a French sphere of influence, when Germany challenged French control in 1905 and 1911. These crises did not cause war but pushed Britain and France closer together in the Entente, deepening the division with Germany.

4. Nationalism

Nationalism is extreme pride in one's country or the desire for self-rule and independence. While it drove unification in Germany and Italy earlier in the century, by 1914, it was deeply destabilizing.

• Great Powers: In countries like Germany and Britain, aggressive nationalism led people to believe their nation was superior and should dominate others. This encouraged rivalry and public support for military action.
• Subject Peoples: In large, multi-ethnic empires (like Austria-Hungary and the Ottoman Empire), subject groups (like the Serbs, Czechs, and Poles) demanded independence. This internal instability threatened to tear the empires apart.

Key Takeaway: Imperialism created worldwide economic and military competition, while Nationalism fueled aggressive foreign policies and internal revolts.

Section 2: Developments in the Balkans (The Powder Keg of Europe)

The Balkans region in Southeastern Europe was the most unstable area in the continent before 1914. Because of all the competing nationalistic and imperialist interests here, it earned the nickname the "Powder Keg of Europe."

Why were the Balkans so volatile?

The Balkans were difficult to solve for the Great Powers because of two overlapping conflicts:

1. The Decline of the Ottoman Empire:
The Ottoman Empire (Turkey) was collapsing, leaving a power vacuum (empty space) in the region. Newly independent small states like Serbia, Bulgaria, and Greece emerged and immediately fought over territory.

2. Rivalry between Great Powers:

• Austria-Hungary (A-H): Feared Nationalism. A-H was a collection of many different ethnic groups. They desperately wanted to stop Serbia from inspiring the Slavs (Serbs, Croats, etc.) inside Austria-Hungary to revolt and demand independence.
• Russia: Supported Pan-Slavism (the movement to unite all Slav people). Russia saw itself as the "Protector of the Slavs" and supported Serbia against A-H, often for access to warm-water ports.

Key Balkan Developments (1890–1914)

1. Bosnian Crisis (1908): Austria-Hungary annexed (formally took over) Bosnia and Herzegovina, territories with a large Slavic population. Serbia was outraged, appealing to Russia, but Russia was too weak to help. This humiliation increased Serbian hatred of A-H.
2. The Balkan Wars (1912–1913): Two quick wars which saw the Balkan states defeat the Ottomans and then fight each other over the spoils. The result was that Serbia became much stronger and much more aggressive, doubling its territory. This terrified Austria-Hungary.

Key Takeaway: The Balkans was a conflict hotspot where A-H’s need to survive clashed directly with Russia’s Pan-Slavic ambitions, dragging the Great Powers towards war.

Section 3: The Short-Term Cause – The Spark

All the long-term factors (MAIN) created the instability, but a single event provided the immediate trigger for war.

The Assassination of Franz Ferdinand (June 28, 1914)

The heir to the Austro-Hungarian throne, Archduke Franz Ferdinand, and his wife Sophie were visiting Sarajevo, the capital of Bosnia.

A Serbian nationalist terrorist group called the Black Hand, aiming to free Bosnia from A-H rule, organized the assassination. The assassin, Gavrilo Princip, succeeded in killing the Archduke and his wife.

The Crisis of July 1914 and the Outbreak of War

The assassination was the spark that set the "powder keg" alight. The following sequence of events shows how the Great Powers reacted, leading to total war.

Step-by-Step Escalation:

1. Austria-Hungary seeks help (July 5): A-H decides to use the assassination as an excuse to crush Serbia. Before acting, they ask Germany for support. Germany issues the "Blank Cheque," promising unconditional support to A-H, essentially encouraging them to attack Serbia.
2. The Ultimatum (July 23): A-H issues a harsh ultimatum (a set of demands) to Serbia, designed to be impossible to accept fully. Serbia accepts most, but not all, demands.
3. War is Declared (July 28): Despite partial acceptance, Austria-Hungary declares war on Serbia.
4. Russian Mobilization (July 29–30): As the "Protector of the Slavs," Russia begins mobilizing its massive army against Austria-Hungary to defend Serbia.
5. Germany Reacts (August 1–3): German war plans required fast action. Seeing Russian mobilization as a threat, Germany declares war on Russia, and two days later, on Russia’s ally, France.
6. Britain is Pulled In (August 4): Germany implements the Schlieffen Plan, which required invading neutral Belgium to bypass French defenses. Britain had guaranteed Belgium’s neutrality. When Germany refused to withdraw, Britain declared war on Germany.