World War I

Table of Contents

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

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

Archduke Franz Ferdinand and his wife, Sophie, duchess of Hohenberg

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?

Learn how the Triple Entente and Triple Alliance evolved into the Allies and Central Powers in World War I

Know about the disastrous Gallipoli Campaign and the role of ANZAC troops in the battles of World War I

World War I: Allied troops on the Gallipoli Peninsula

Listen to a Turkish perspective on the Gallipoli Campaign, known to Turkish people as the Battle of Çanakkale, 1915–16

Learn about the use of animals especially among the ANZAC soldiers during World War I

Mabel St. Clair Stobart: Women's fight for rights on the battlefield

Examine how German U-boats and the Zimmerman Telegram pushed the United States into World War I

Learn how U.S. troops helped Allied forces push Germany out of France and force an armistice

A 1917 Albatros D.Va, a German fighter plane of World War I.

Australia and New Zealand Army Corps troops

U.S. 27th Infantry Division after the end of World War I

Compare the U.S. death toll during major events

Hiking a historic trail in the Carnic Alps

Know about the stigma and impact associated with combat fatigue (shell shock) and the changing perceptions of society towards it

Examine the conflict between U.S. President Wilson and Congress in the aftermath of World War I

Learn about the treatment for combat fatigue (shell shock) administered to British soldiers in WWI

Examine how the Allied powers dismembered the Central Powers of World War I by a treaty that failed to prevent World War II

What were the consequences of the Treaty of Versailles?

Watch the American Expeditionary Force sail across the Atlantic to join the Allies in World War I

View historical footage and photographs surrounding Gavrilo Princip's assassination of Archduke Franz Ferdinand

For Students

Key Facts of World War I

World War I Timeline

Causes and Effects of World War I

World War I: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Last Updated: Jun 19, 2025

News •

'Big Short' investor warns the precarious tariff environment reminds him of WWI—and a trade war would send the U.S. into a recession • June 18, 2025, 9:09 AM ET (Fortune)

WW1 soldier's remains found on French building site • June 12, 2025, 4:58 AM ET (BBC)

Thieves steal 185-year-old church bell from Paterson's deconsecrated St Ann's Church • June 9, 2025, 9:45 AM ET (ABC News (Australia))

School unveils war memorial for former pupils killed in wars • June 8, 2025, 2:28 AM ET (BBC)

Volunteers spent 25 years building a WWI replica plane. It just took flight. • June 7, 2025, 1:38 AM ET (Popular Science)

Facts

Also Known As	Great War • First World War • WWI
Date	July 28, 1914 - November 11, 1918
Participants	Bulgaria • France • Germany • Italy • Japan • Ottoman Empire • Portugal • Russia • United Kingdom • United States

Did You Know?

When World War 1 began in the summer of 1914, most people assumed the war would be finished by Christmas.
The booming of the artillery at the Western front could sometimes be heard all the way back in Britain.
German and British soldiers called a truce on Christmas in 1914 and played a soccer game together.