1914–1918
The war lasted more than four years, ending with the Armistice of 11 November 1918.
A global conflict that transformed empires, borders, societies and international politics, leaving a lasting mark on the modern world.
EXPLORE THE GREAT WAR ↓A conflict that began in Europe and expanded into a war involving powers and territories across the world.
The war lasted more than four years, ending with the Armistice of 11 November 1918.
Fighting and military operations took place across Europe, the Middle East, Africa and other regions.
Major belligerents included the Allied Powers and the Central Powers, although alliances changed and expanded during the conflict.
The war contributed to the collapse of several major empires and reshaped the political map of Europe and the Middle East.
In the decades before 1914, European powers competed for influence, territory and economic strength. Nationalism became a powerful political force while military planning and alliances increased tensions.
Rivalries between major powers were especially strong in regions such as the Balkans, where the decline of the Ottoman Empire and competing national movements created a volatile political environment.
Europe became divided into interconnected alliance systems. The existence of these alliances meant that a crisis involving one power could quickly draw additional states into conflict.
No single cause explains the outbreak of the war. Several long-term tensions combined with a major political crisis in 1914.
Nationalist movements strengthened demands for political independence and contributed to rivalry between European powers.
Major powers expanded their armed forces and developed detailed military plans, increasing the importance of military power in international politics.
Rival alliance systems and competition between European empires created a political environment in which a regional crisis could rapidly become an international conflict.
On 28 June 1914, Archduke Franz Ferdinand of Austria and his wife Sophie were assassinated in Sarajevo by Gavrilo Princip. The crisis that followed set off a chain of diplomatic decisions and declarations of war.
Major turning points from the outbreak of war to the Armistice.
Austria-Hungary declared war on Serbia in July. A series of mobilizations and declarations brought the major European powers into the conflict.
Italy entered the war on the Allied side, while fighting continued across the Western and Eastern Fronts and in the Middle East.
The battles of Verdun and the Somme became symbols of the enormous scale and human cost of industrialized warfare.
The United States entered the war in April, while revolution in Russia eventually led to Russia's withdrawal from the conflict.
Germany's spring offensives failed to achieve victory. Allied advances and the collapse of the Central Powers led to the Armistice.
The Armistice came into effect on 11 November 1918, ending major fighting on the Western Front.
Industrial technology changed the scale, speed and character of warfare.
Rapid-fire weapons made direct assaults across exposed ground extremely difficult and contributed to the development of trench warfare.
Armored vehicles were introduced on the Western Front in an attempt to overcome defensive positions and restore mobility to the battlefield.
Aircraft were increasingly used for reconnaissance, artillery observation, air combat and eventually bombing missions.
On the Western Front, armies constructed extensive trench systems. Opposing forces faced one another across a heavily defended zone that remained relatively stable for long periods.
Battles such as Verdun and the Somme demonstrated the destructive power of modern artillery, machine guns and mass armies.
Large-scale fighting between Germany, Austria-Hungary and Russia produced major movements across Eastern Europe.
The Ottoman Empire fought against the Allied powers in campaigns across the Middle East, including Mesopotamia, Palestine and Arabia.
Fighting also occurred in African colonies while naval warfare and the German U-boat campaign affected international shipping.
The war affected entire societies, not only soldiers on the battlefield.
Governments directed enormous resources toward military production, transportation and supplies.
Millions of civilians contributed to wartime industries, agriculture, medical services and other essential activities.
Governments used newspapers, posters and other forms of communication to influence public opinion and maintain support for the war.
World War I caused immense military and civilian losses and left large parts of Europe economically and socially devastated.
The German, Austro-Hungarian, Ottoman and Russian Empires experienced major political transformations or collapse during and after the war.
The Treaty of Versailles and other post-war settlements redrew borders and created new political arrangements. The League of Nations was established as part of the post-war international order.
The unresolved political and economic tensions of the post-war era would continue to influence international affairs for decades.
World War I transformed warfare, diplomacy, economies and societies across the globe.
Its consequences shaped the political landscape of the twentieth century and influenced events that would follow, including the rise of new states, revolutionary movements and eventually another world war.
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