World War I | History, Summary, Causes, Combatants, Casualties, Map, & Facts (2024)

World War I

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Also called:
First World War or Great War
July 28, 1914 - November 11, 1918
Ottoman Empire
United Kingdom
United States
Major Events:
Gallipoli Campaign
First Battle of the Somme
Battle of Verdun
Christmas Truce
Battle of Passchendaele
Key People:
Kemal Atatürk
Winston Churchill
Georges Clemenceau
Franz Joseph
David Lloyd George

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Top Questions

What was the main cause of World War I?

World War I began after the assassination of Austrian archduke Franz Ferdinand by South Slav nationalist Gavrilo Princip on June 28, 1914.

Read more below:The outbreak of war

Balkan WarsRead more about why the Balkans became the “powder keg of Europe.”

What countries fought in World War I?

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).

Read more below:The outbreak of war: Forces and resources of the combatant nations in 1914

Who won World War I?

The Allies won World War I after four years of combat and the deaths of some 8.5 million soldiers as a result of battle wounds or disease.

Treaty of VersaillesRead more about the Treaty of Versailles. In many ways, the peace treaty that ended World War I set the stage for World War II.

How many people died during World War I?

Some 8,500,000 soldiers died as a result of wounds or disease during World War I. Perhaps as many as 13,000,000 civilians also died. This immensely large number of deaths dwarfed that of any previous war, largely because of the new technologies and styles of warfare used in World War I.

Read more below:The last offensives and the Allies’ victory: Killed, wounded, and missing

Read more below:The outbreak of war: Technology of war in 1914

trench warfareRead more about trench warfare.

What was the significance of World War I?

Four imperial dynasties—the Habsburgs of Austria-Hungary, the Hohenzollerns of Germany, the sultanate of the Ottoman Empire, and the Romanovs of Russia—collapsed as a direct result of the war, and the map of Europe was changed forever. The United States emerged as a world power, and new technology made warfare deadlier than ever before.

Remembering World War IRead more about the effects of World War I.



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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 War I was one of the great watersheds of 20th-century geopolitical history. It led to the fall of four great imperial dynasties (in Germany, Russia, Austria-Hungary, and Turkey), resulted in the Bolshevik Revolution in Russia, and, in its destabilization of European society, laid the groundwork for World War II.

The last surviving veterans of World War I were American serviceman Frank Buckles (died in February 2011), British-born Australian serviceman Claude Choules (died in May 2011), and British servicewoman Florence Green (died in February 2012), the last surviving veteran of the war.

The outbreak of war

With Serbia already much aggrandized by the two Balkan Wars (1912–13, 1913), Serbian nationalists turned their attention back to the idea of “liberating” the South Slavs of Austria-Hungary. Colonel Dragutin Dimitrijević, head of Serbia’s military intelligence, was also, under the alias “Apis,” head of the secret society Union or Death, pledged to the pursuit of this pan-Serbian ambition. Believing that the Serbs’ cause would be served by the death of the Austrian archduke Franz Ferdinand, heir presumptive to the Austrian emperor Franz Joseph, and learning that the Archduke was about to visit Bosnia on a tour of military inspection, Apis plotted his assassination. Nikola Pašić, the Serbian prime minister and an enemy of Apis, heard of the plot and warned the Austrian government of it, but his message was too cautiously worded to be understood.

Britannica Quiz41 Questions from Britannica’s Most Popular World History Quizzes

At 11:15 am on June 28, 1914, in the Bosnian capital, Sarajevo, Franz Ferdinand and his morganatic wife, Sophie, duch*ess of Hohenberg, were shot dead by a Bosnian Serb, Gavrilo Princip. The chief of the Austro-Hungarian general staff, Franz, Graf (count) Conrad von Hötzendorf, and the foreign minister, Leopold, Graf von Berchtold, saw the crime as the occasion for measures to humiliate Serbia and so to enhance Austria-Hungary’s prestige in the Balkans. Conrad had already (October 1913) been assured by William II of Germany’s support if Austria-Hungary should start a preventive war against Serbia. This assurance was confirmed in the week following the assassination, before William, on July 6, set off upon his annual cruise to the North Cape, off Norway.

The Austrians decided to present an unacceptable ultimatum to Serbia and then to declare war, relying on Germany to deter Russia from intervention. Though the terms of the ultimatum were finally approved on July 19, its delivery was postponed to the evening of July 23, since by that time the French president, Raymond Poincaré, and his premier, René Viviani, who had set off on a state visit to Russia on July 15, would be on their way home and therefore unable to concert an immediate reaction with their Russian allies. When the delivery was announced, on July 24, Russia declared that Austria-Hungary must not be allowed to crush Serbia.

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Serbia replied to the ultimatum on July 25, accepting most of its demands but protesting against two of them—namely, that Serbian officials (unnamed) should be dismissed at Austria-Hungary’s behest and that Austro-Hungarian officials should take part, on Serbian soil, in proceedings against organizations hostile to Austria-Hungary. Though Serbia offered to submit the issue to international arbitration, Austria-Hungary promptly severed diplomatic relations and ordered partial mobilization.

Home from his cruise on July 27, William learned on July 28 how Serbia had replied to the ultimatum. At once he instructed the German Foreign Office to tell Austria-Hungary that there was no longer any justification for war and that it should content itself with a temporary occupation of Belgrade. But, meanwhile, the German Foreign Office had been giving such encouragement to Berchtold that already on July 27 he had persuaded Franz Joseph to authorize war against Serbia. War was in fact declared on July 28, and Austro-Hungarian artillery began to bombard Belgrade the next day. Russia then ordered partial mobilization against Austria-Hungary, and on July 30, when Austria-Hungary was riposting conventionally with an order of mobilization on its Russian frontier, Russia ordered general mobilization. Germany, which since July 28 had still been hoping, in disregard of earlier warning hints from Great Britain, that Austria-Hungary’s war against Serbia could be “localized” to the Balkans, was now disillusioned insofar as eastern Europe was concerned. On July 31 Germany sent a 24-hour ultimatum requiring Russia to halt its mobilization and an 18-hour ultimatum requiring France to promise neutrality in the event of war between Russia and Germany.

Both Russia and France predictably ignored these demands. On August 1 Germany ordered general mobilization and declared war against Russia, and France likewise ordered general mobilization. The next day Germany sent troops into Luxembourg and demanded from Belgium free passage for German troops across its neutral territory. On August 3 Germany declared war against France.

In the night of August 3–4 German forces invaded Belgium. Thereupon, Great Britain, which had no concern with Serbia and no express obligation to fight either for Russia or for France but was expressly committed to defend Belgium, on August 4 declared war against Germany.

Austria-Hungary declared war against Russia on August 5; Serbia against Germany on August 6; Montenegro against Austria-Hungary on August 7 and against Germany on August 12; France and Great Britain against Austria-Hungary on August 10 and on August 12, respectively; Japan against Germany on August 23; Austria-Hungary against Japan on August 25 and against Belgium on August 28.

Romania had renewed its secret anti-Russian alliance of 1883 with the Central Powers on February 26, 1914, but now chose to remain neutral. Italy had confirmed the Triple Alliance on December 7, 1912, but could now propound formal arguments for disregarding it: first, Italy was not obliged to support its allies in a war of aggression; second, the original treaty of 1882 had stated expressly that the alliance was not against England.

On September 5, 1914, Russia, France, and Great Britain concluded the Treaty of London, each promising not to make a separate peace with the Central Powers. Thenceforth, they could be called the Allied, or Entente, powers, or simply the Allies.

The outbreak of war in August 1914 was generally greeted with confidence and jubilation by the peoples of Europe, among whom it inspired a wave of patriotic feeling and celebration. Few people imagined how long or how disastrous a war between the great nations of Europe could be, and most believed that their country’s side would be victorious within a matter of months. The war was welcomed either patriotically, as a defensive one imposed by national necessity, or idealistically, as one for upholding right against might, the sanctity of treaties, and international morality.

World War I | History, Summary, Causes, Combatants, Casualties, Map, & Facts (2024)


What was the summary of the World War 1? ›

World War I was one of the great watersheds of 20th-century geopolitical history. It led to the fall of four great imperial dynasties (in Germany, Russia, Austria-Hungary, and Turkey), resulted in the Bolshevik Revolution in Russia, and, in its destabilization of European society, laid the groundwork for World War II.

What was the main cause of casualties in ww1? ›

Most of the casualties during WWI are due to war related famine and disease. Civilian deaths due to the Spanish flu have been excluded from these figures, whenever possible. Moreover, civilian deaths include the Armenian Genocide.

What were the main causes of World War I? ›

The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary. In June 1914, a Serbian-nationalist terrorist group called the Black Hand sent groups to assassinate the Archduke.

What were the causes of World War 1 National Geographic? ›

World War I had a variety of causes, but its roots were in a complex web of alliances between European powers. At its core was mistrust between—and militarization in—the informal “Triple Entente” (Great Britain, France, and Russia) and the secret “Triple Alliance” (Germany, the Austro-Hungarian Empire, and Italy).

How We Entered World War 1 summary? ›

The US entered World War I because Germany embarked on a deadly gamble. Germany sank many American merchant ships around the British Isles which prompted the American entry into the war.

What was the #1 killer in WW1? ›

By far, artillery was the biggest killer in World War I, and provided the greatest source of war wounded.

Why were deaths so high in WW1? ›

One reason is that, compared to previous conflicts, “warfare had become more technologically advanced,” Green explains. “World War I was the first with trench warfare, large use of submarines and airplanes, and poison gas, as well as flamethrowers and machine guns.”

What battle in ww1 caused the most deaths? ›

The first day of the Somme was a catastrophe for the British Army and a shock for all the Allies. Despite the limited Allied gains, German forces had also suffered horribly. The British pressed the attack for months, well into the fall. By the time the battle ended, each side had suffered more than 600,000 casualties.

What was the main cause of World War 1 essay? ›

The main causes of World War 1 were alliances between countries, militarism, nationalism, imperialism, secret diplomacy, and internationalism. The assassination of Archduke Franz Ferdinand, heir to the throne of Austria-Hungary, by Gavrilo Princip in Bosnia is widely accepted as the starting point for World War I.

Why was Germany blamed for WW1? ›

The largest share of responsibility lies with the German government. Germany's rulers made possible a Balkan war by urging Austria-Hungary to invade Serbia, well understanding that such a conflict might escalate. Without German backing it is unlikely that Austria-Hungary would have acted so drastically.

How did assassination lead to WW1? ›

Just hours after narrowly escaping an assassin's bomb, Archduke Franz Ferdinand, the heir to Austro-Hungarian throne and his wife, the duch*ess of Hohenberg, are killed by Gavrilo Princip. A month later, Austria-Hungary declares war on Serbia and Europe rapidly descends into chaos. Read more about it!

What was the main event that caused World War 1? ›

The spark that ignited World War I was struck in Sarajevo, Bosnia, where Archduke Franz Ferdinand—heir to the Austro-Hungarian Empire—was shot to death along with his wife, Sophie, by the Serbian nationalist Gavrilo Princip on June 28, 1914.

What were the geographic causes of ww1? ›

Due to geographical closeness, Germany, Austria-Hungary, and Italy came together as the Triple Alliance and later became the Central powers due to their central positioning in Europe. France and Britain became allies along with Russia in order to defend their borders and support each other in case of war.

What is World War 1 mainly about? ›

For four years, from 1914 to 1918, World War I raged across Europe's western and eastern fronts after growing tensions and then the assassination of Archduke Franz Ferdinand of Austria ignited the war.

What is World War 1 Short answer? ›

The First World War was the first truly global conflict. From 1914 to 1918, fighting took place across several continents, at sea and, for the first time, in the air. This was war on an unprecedented scale, with battles often lasting months instead of days.

What was the main goal of World War 1? ›

All countries had territorial aims: to evacuate the Germans from Belgium, to restore Alsace-Lorraine to France, for Italy to get the Trentino, and so on. They also wanted to restore their defeated allies, Serbia and Romania, ideally with extra territory.

What was the point of World War 1? ›

Austria-Hungary wanted to conquer Serbia and eliminate the threat of South Slav nationalism to the Hapsburg state. Tsarist Russia wanted to defend Slavic, Orthodox Serbia against the Hapsburgs. The conflict between them drew in their respective allies, Germany and France.


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