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

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

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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

News •

Morocco identifies preliminary sites of nine WWI shipwrecks off southern coast • Feb. 20, 2025, 8:33 AM ET (Jerusalem Post)

9 shipwrecks from World War I discovered off Morocco's southern coast • Feb. 18, 2025, 3:16 AM ET (CBS)

How Spanish king became last hope for missing World War One soldiers' relatives • Feb. 13, 2025, 9:46 AM ET (Straits Times)

Air pollution kills as many people every year as the world wars did: Sonam Wangchuk • Feb. 9, 2025, 9:52 PM ET (The Indian Express)

Adelaide RSL searches for origins of 121-year-old diary from WWI left on doorstep • Feb. 8, 2025, 1:40 AM ET (ABC News (Australia))

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.

Photos and Videos

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

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Topics

U-boat zeppelin All Quiet on the Western Front In Flanders Fields

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Timeline

Battle of the Frontiers

August 4, 1914 - September 6, 1914

Battle of Mons

August 23, 1914

Battle of Tannenberg

August 26, 1914 - August 30, 1914

First Battle of the Marne

September 6, 1914 - September 12, 1914

First Battle of Ypres

October 19, 1914 - November 22, 1914

Battle of Tanga

November 2, 1914 - November 5, 1914

Battle of the Falkland Islands

December 8, 1914

Christmas Truce

December 24, 1914 - December 25, 1914

World War I: Allied troops on the Gallipoli Peninsula

Gallipoli Campaign

February 16, 1915 - January 9, 1916

naval operations in the Dardanelles Campaign

February 19, 1915 - March 18, 1915

Second Battle of Ypres

April 22, 1915 - May 25, 1915

Battles of the Isonzo

June 23, 1915 - October 24, 1917

Australia and New Zealand Army Corps troops

Battle of Lone Pine

August 6, 1915 - August 10, 1915

Battle of Verdun

February 21, 1916 - December 18, 1916

Battle of Jutland

May 31, 1916 - June 1, 1916

Brusilov Offensive

June 4, 1916 - August 10, 1916

First Battle of the Somme

July 1, 1916 - November 13, 1916

Battle of Messines

June 7, 1917 - June 14, 1917

June Offensive

July 1, 1917 - c. July 4, 1917

Battle of Passchendaele

July 31, 1917 - November 6, 1917

Battle of Caporetto

October 24, 1917 - December 19, 1917

Battle of Cambrai

November 20, 1917 - December 8, 1917

treaties of Brest-Litovsk

February 9, 1918; March 3, 1918

Battle of Belleau Wood

June 1, 1918 - June 26, 1918

Battle of Amiens

August 8, 1918 - August 11, 1918

Battle of Saint-Mihiel

September 12, 1918 - September 16, 1918

Battle of Cambrai

September 27, 1918 - October 11, 1918

Battle of Mons

November 11, 1918

Key People

Winston Churchill

prime minister of United Kingdom

Kemal Atatürk

president of Turkey

Woodrow Wilson

president of United States

David Lloyd George

prime minister of United Kingdom

Georges Clemenceau

prime minister of France

Franz Joseph

emperor of Austria-Hungary

George Patton

United States general

Herbert Hoover

president of United States

William II

emperor of Germany

Nicholas II

tsar of Russia

Jan Smuts

South African statesman

Erich Ludendorff

German general

Nikola Pašić

prime minister of Serbia

H.H. Asquith, 1st earl of Oxford and Asquith

prime minister of United Kingdom

Ferdinand Foch

marshal of France

Paul von Hindenburg

German president

John J. Pershing

United States general

Eleuthérios Venizélos

prime minister of Greece

Philippe Pétain

French general

William Mitchell

United States Army general

Causes and Effects

Causes

A naval arms race between Great Britain and the German Empire made conflict on the high seas almost inevitable.
German success in the Franco-German War fostered a belief in the supremacy of Prussian militarism.
Germany's annexation of Alsace-Lorraine after the Franco-German War aroused a deep longing for revenge in the French people.
The Balkan Wars virtually eradicated the Ottoman presence in Europe, but led to violent strife among the victors.
The assassination of Austrian archduke Franz Ferdinand by South Slav nationalist Gavrilo Princip on June 28, 1914.

Effects

As many as 8.5 million soldiers and 13 million civilians died as a result of the war.
Failure to deliver mandated reparations leads to the armed occupation of the Ruhr River valley region by French and Belgian troops.
German militarists perpetuate the myth that the German Army was undefeated in battle, undermining faith in the civilian government of the Weimar Republic.
Imperial dynasties in Austria-Hungary, Germany, the Ottoman Empire, and Russia collapsed.
Mass movement of troops and refugees helped spread the Spanish flu, a devastating influenza pandemic that claimed as many as 50 million lives in 1918-19.
Ottoman territories in the Middle East are divvied up among the victorious Allied powers at the Conference of San Remo.
The League of Nations is established, but its effectiveness is hampered by the non-participation of the United States.

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