World War I

Introduction & Top Questions
The outbreak of war
- Forces and resources of the combatant nations in 1914
- Technology of war in 1914
The initial stages of the war
- Initial strategies
  - The Schlieffen Plan
  - Eastern Front strategy, 1914
  - The strategy of the Western Allies, 1914
- The war in the west, 1914
  - The German invasion
  - The First Battle of the Marne
- The Eastern and other fronts, 1914
  - The war in the east, 1914
  - The Serbian campaign, 1914
  - The Turkish entry
  - The war at sea, 1914–15
  - The loss of the German colonies
The years of stalemate
- Rival strategies and the Dardanelles campaign, 1915–16
- The Western and Eastern fronts, 1915
  - The Western Front, 1915
  - The Eastern Front, 1915
- Other fronts, 1915–16
  - The Caucasus, 1914–16
  - Mesopotamia, 1914–April 1916
  - The Egyptian frontiers, 1915–July 1917
  - Italy and the Italian front, 1915–16
  - Serbia and the Salonika expedition, 1915–17
- Major developments in 1916
  - The Western Front, 1916
  - The Battle of Jutland
  - The Eastern Front, 1916
  - German strategy and the submarine war, 1916–January 1917
  - Peace moves and U.S. policy to February 1917
- Developments in 1917
  - The Western Front, January–May 1917
  - The U.S. entry into the war
  - The Russian revolutions and the Eastern Front, March 1917–March 1918
  - Greek affairs
  - Caporetto
  - Mesopotamia, summer 1916–winter 1917
  - Palestine, autumn 1917
  - The Western Front, June–December 1917
  - The Far East
  - Naval operations, 1917–18
  - Air warfare
  - Peace moves, March 1917–September 1918
The last offensives and the Allies’ victory
- The Western Front, March–September 1918
- Other developments in 1918
  - Czechs, Yugoslavs, and Poles
  - Eastern Europe and the Russian periphery, March–November 1918
  - The Balkan front, 1918
  - The Turkish fronts, 1918
  - Vittorio Veneto
  - The collapse of Austria-Hungary
- The final offensive on the Western Front
  - The end of the German war
  - The Armistice
- Killed, wounded, and missing

References & Edit History Quick Facts & Related Topics

Images, Videos & Interactives

Infographic summarizing World War I with sections on the war's onset, technological firsts, and major events. Includes a timeline from 1914 to 1918, maps showing the global spread of the conflict, and pie charts displaying casualty percentages for major countries and alliances. At the bottom, two maps compare Europe's borders in 1914 and 1919. The design uses red and green tones to differentiate allies, central powers, and neutral countries.

Women of World War I: Marie Curie, Mabel St. Clair Stobart, and Aileen Cole Stewart

Franz Ferdinand, archduke of Austria-Este, and his wife Sophie ride in an open carriage in Sarajevo, both dressed formally, with a man standing beside the carriage.

Causes and start of World War I

Maxim machine gun

Three soldiers in World War I uniforms and helmets operate a St. Etienne machine gun in a trench at the Somme.

See how No Man's Land between World War I trenches led to the use of chemical weapons, tanks, and warplanes

When was the motorized ambulance invented?

At a Glance

Franz Ferdinand, archduke of Austria-Este, and his wife Sophie ride in an open carriage in Sarajevo, both dressed formally, with a man standing beside the carriage.

World War I Timeline

World War I

Key Facts of World War I

Paris Peace Conference

Causes and Effects of World War I

Related Questions

World War I — World War I A British soldier inside a trench on the Western Front during World War I, 1914–18.

World War I

1914–1918

Also known as: First World War, Great War, WWI

Written by

Dennis E. ShowalterAll

Fact-checked by

Britannica Editors

Last updated

Nov. 13, 2026 •History

World War I, an international conflict that in 1914–18 embroiled most of the nations of Europe along with Russia, the United States, the Middle East, and other regions. The war pitted the Central Powers—mainly Germany, Austria-Hungary, and Turkey—against the Allies—mainly France, Great Britain, Russia, Italy, Japan, and, from 1917, the United States. It ended with the defeat of the Central Powers. The war was virtually unprecedented in the slaughter, carnage, and destruction it caused. World...

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