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World History · 1914–1918
World War I: The Great War
A single pistol shot in Sarajevo set off a war that pulled in the great powers of Europe and their empires, killed about nine to ten million soldiers and redrew the map of the world. Start here for the causes, the fronts, the battles, the people, the weapons and the ships of the war that people at the time simply called the Great War.
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“I Want You for U.S. Army,” James Montgomery Flagg’s 1917 recruiting poster
Quick facts
World War I at a glance
| When | July 28, 1914 to November 11, 1918 (Armistice); peace treaties signed 1919–1920 | |
| Where | Mainly Europe (Western, Eastern and Italian fronts), plus the Middle East, Africa, Asia and the oceans | |
| Allies | France, Britain and its empire, Russia (to 1917), Serbia, Belgium, Japan, Italy (from 1915), United States (from 1917) | |
| Central Powers | Germany, Austria-Hungary, the Ottoman Empire (from late 1914), Bulgaria (from 1915) | |
| Spark | Assassination of Archduke Franz Ferdinand in Sarajevo, June 28, 1914 | |
| Mobilized | About 65 million men served in uniform | |
| Dead | About 9 to 10 million soldiers and millions of civilians | |
| Ended by | The Armistice of November 11, 1918, and the Treaty of Versailles, June 28, 1919 |
The big picture in 30 seconds
Why World War I matters
- It destroyed four empires: Germany, Austria-Hungary, Russia and the Ottoman Empire.
- It brought machine guns, poison gas, tanks, submarines and air war on a scale never seen before.
- It made the United States a world power and led to the Russian Revolution of 1917.
- Its unfinished business, especially the Treaty of Versailles, helped set the stage for World War II.
65 million
soldiers mobilized
9–10 million
military dead
4
empires collapsed
1,568
days of war, 1914–1918
How it started
The causes of the war
Historians often sum up the long-term causes with the letters M-A-I-N: militarism, alliances, imperialism and nationalism. None of them made war certain, but together they turned a crisis in the Balkans into a world war in just five weeks.
M
Militarism
The great powers built huge conscript armies and detailed war plans. Germany and Britain raced to build dreadnought battleships.
A
Alliances
Europe split into two camps: the Triple Entente (France, Russia, Britain) and the Triple Alliance (Germany, Austria-Hungary, Italy).
I
Imperialism
Rivalry over colonies in Africa and Asia, and over the crumbling Ottoman Empire, fed suspicion between the powers.
N
Nationalism
Pride and ethnic loyalties ran high. Serbian nationalists wanted to free fellow South Slavs from Austro-Hungarian rule.
The spark
Sarajevo and the July Crisis
On June 28, 1914, Archduke Franz Ferdinand, heir to the throne of Austria-Hungary, and his wife Sophie were shot dead in Sarajevo, Bosnia, by Gavrilo Princip, a 19-year-old Bosnian Serb linked to a secret Serbian nationalist group, the Black Hand. Austria-Hungary blamed Serbia and, with a promise of support from Germany (the so-called “blank check”), sent Serbia a harsh ultimatum.
Then the alliance system took over. Austria-Hungary declared war on Serbia on July 28. Russia mobilized to protect Serbia. Germany declared war on Russia on August 1 and on France on August 3, and marched through neutral Belgium to reach France. That invasion brought Britain into the war on August 4. In five weeks a murder in the Balkans had become a European war.
Who fought and where
Two alliances, many fronts
The war was fought on several fronts at once. On the Western Front, a line of trenches ran about 440 miles from the Belgian coast to the Swiss border and barely moved for more than three years. On the Eastern Front, Germany and Austria-Hungary fought Russia across a much longer, more mobile line until Russia quit in 1918. Other fronts ran through the Alps against Italy, the Balkans, Gallipoli, Mesopotamia, Palestine and Africa, while navies fought for control of the seas.
Simplified map. Red dots mark battles with their own pages.
Key battles
The battles that shaped the war
Each card opens a full page with quick facts, a map, the story of the fighting, the commanders and why it mattered.
The United States in the Great War
America goes “Over There”
When war broke out, President Woodrow Wilson declared the United States neutral, and most Americans wanted to stay out. But German submarine warfare kept pulling the country in. On May 7, 1915, a U-boat sank the British liner Lusitania, killing 1,198 people, 128 of them Americans. In early 1917 Germany resumed unrestricted submarine warfare, and British codebreakers revealed the Zimmermann Telegram, in which Germany offered Mexico an alliance and the return of Texas, New Mexico and Arizona.
On April 2, 1917, Wilson asked Congress for war, and it declared war on Germany on April 6. The country built an army almost from scratch through the draft. General John J. Pershing’s American Expeditionary Forces (AEF) grew to about two million men in France by November 1918. Fresh American “doughboys” helped stop Germany’s last offensives and then drove forward at St. Mihiel and the Meuse-Argonne. About 116,000 Americans died, roughly half of them from disease, especially the 1918 influenza.
Key people
Leaders and legends of the Great War
Kings and presidents, generals and ordinary soldiers who became famous. Meet many more on the full Key People page.
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Weapons and ships
The machines of a new kind of war
World War I was the first great industrial war. Factories turned out shells by the billion, and inventors raced to break the deadlock of the trenches with new weapons on land, in the air and under the sea.
The human cost
A generation lost
No war before had killed so many soldiers. Whole villages in Britain lost most of their young men, France lost about one in six of the men it mobilized, and millions came home wounded, disabled or shell-shocked. Disease, famine and the 1918 influenza pandemic killed millions more civilians as the war ended.
“The world must be made safe for democracy.”
Woodrow Wilson
Asking Congress to declare war on Germany, April 2, 1917
Year by year
World War I timeline
After the war
The peace and its legacy
At the Paris Peace Conference of 1919, the “Big Four” (Wilson, Britain’s David Lloyd George, France’s Georges Clemenceau and Italy’s Vittorio Orlando) wrote the peace. The Treaty of Versailles made Germany accept blame for the war, pay reparations, give up territory and its colonies, and limit its army to 100,000 men. Other treaties broke up Austria-Hungary and the Ottoman Empire. New nations such as Poland, Czechoslovakia and Yugoslavia appeared on the map.
Wilson’s dream, a League of Nations to keep the peace, was created, but the U.S. Senate refused to ratify the treaty and the United States never joined. Many Germans saw the treaty as a humiliation, a resentment that Adolf Hitler would exploit. Twenty years after the Armistice, Europe was at war again.
The American side
Industry, Immigration and WWI
Our U.S. History era page covers America from 1880 to 1919, including the home front, the draft and the war’s effect on American life.
Go deeper
Books and sources
- The Guns of August, by Barbara Tuchman (1962)
- The First World War, by John Keegan (1998)
- A World Undone, by G. J. Meyer (2006)
- The Sleepwalkers, by Christopher Clark (2012)
- More recommended books