First World War I .

"World War One", "Great War", and "WW1" redirect here. For other uses, see World War One (disambiguation), Great War (disambiguation), and WW1 (album).

World War I Clockwise from the top: The aftermath of shelling during the Battle of the Somme, Mark V tanks cross the Hindenburg Line, HMS Irresistible sinks after hitting a mine in the Dardanelles, a British Vickers machine gun crew wears gas masks during the Battle of the Somme, Albatros D.III fighters of Jagdstaffel 11 Date 28 July 1914 – 11 November 1918 (4 years, 3 months and 2 weeks) Peace treaties[show] Location Europe, Africa, the Middle East, the Pacific Islands, China, Indian Ocean, and off the coast of South and North America Result Allied victory Central Powers' victory on the Eastern Front nullified by defeat on the Western Front Fall of the German, Russian, Ottoman, and Austro-Hungarian empires Russian Civil War and foundation of Soviet Union Formation of new countries in Europe and the Middle East Transfer of German colonies and regions of the former Ottoman Empire to other powers Establishment of the League of Nations. (more...) Belligerents Allied Powers  France  British Empire  Russia (until 1917)  Serbia  Montenegro  Belgium  Japan  Italy (1915–18)  Portugal (1916–18)  Romania (1916–18) Hejaz (1916–18)  China (1917–18)  Greece (1917–18) Siam (1917–18)  United States (1917–18) ...and others Central Powers  German Empire  Austria-Hungary  Ottoman Empire  Bulgaria (1915–18) ...and co-belligerents Commanders and leaders Allied leaders Raymond Poincaré Georges Clemenceau George V H. H. Asquith David Lloyd George Nicholas II Victor Emmanuel III Vittorio Orlando Woodrow Wilson Yoshihito Peter I Ferdinand I Duan Qirui Constantine I Eleftherios Venizelos Nicholas I ...and others Central Powers leaders Wilhelm II Franz Joseph I † Karl I Mehmed V † Three Pashas Ferdinand I ...and others Strength 12,000,000 8,841,541[1][2] 8,660,000[3] 5,615,140 4,743,826 1,234,000 800,000 707,343 380,000 250,000 50,000 Total: 42,959,850[4] 13,250,000 7,800,000 2,998,321 1,200,000 Total: 25,248,321[4] Casualties and losses Military dead: 5,525,000 Military wounded: 12,831,500 Military missing: 4,121,000 Total: 22,477,500 KIA, WIA or MIA ...further details. Military dead: 4,386,000 Military wounded: 8,388,000 Military missing: 3,629,000 Total: 16,403,000 KIA, WIA or MIA ...further details.

[show] v t e Theatres of World War I

Events leading to World War I
Triple Alliance 1882 Franco-Russian Alliance 1894 Anglo-German naval arms race 1898–1912 Venezuela Naval Blockade 1902–1903 Entente Cordiale 1904 Russo-Japanese War 1904–1905 First Moroccan Crisis 1905–1906 Anglo-Russian Entente 1907 Bosnian crisis 1908–1909 Agadir Crisis 1911 Italo-Turkish War 1911–1912 Balkan Wars 1912–1913 Assassination of Franz Ferdinand 1914 July Crisis 1914
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World War I (WWI or WW1), also known as the First World War, the Great War, or the War to End All Wars,^[5] was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. More than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history.^[6][7] Over nine million combatants and seven million civilians died as a result of the war (including the victims of a number of genocides), a casualty rate exacerbated by the belligerents' technological and industrial sophistication, and the tactical stalemate caused by gruelling trench warfare. It was one of the deadliest conflicts in history, and paved the way for major political changes, including revolutions in many of the nations involved. Unresolved rivalries still extant at the end of the conflict contributed to the start of the Second World War only twenty-one years later.^[8]
The war drew in all the world's economic great powers,^[9] assembled in two opposing alliances: the Allies (based on the Triple Entente of the Russian Empire, the French Third Republic, and the United Kingdom of Great Britain and Ireland) versus the Central Powers of Germany and Austria-Hungary. Although Italy was a member of the Triple Alliance alongside Germany and Austria-Hungary, it did not join the Central Powers, as Austria-Hungary had taken the offensive against the terms of the alliance.^[10] These alliances were reorganised and expanded as more nations entered the war: Italy, Japan and the United States joined the Allies, while the Ottoman Empire and Bulgaria joined the Central Powers.
The trigger for the war was the assassination of Archduke Franz Ferdinand of Austria, heir to the throne of Austria-Hungary, by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914. This set off a diplomatic crisis when Austria-Hungary delivered an ultimatum to the Kingdom of Serbia,^[11][12] and entangled international alliances formed over the previous decades were invoked. Within weeks the major powers were at war, and the conflict soon spread around the world.
Russia was the first to order a partial mobilization of its armies on 24-25 July, and when on 28 July Austro-Hungary declared war on Serbia, Russia declared general mobilization on 30 July.^[13] Germany presented an ultimatum to Russia to demobilise, and when this was refused, declared war on Russia on 1 August. Being outnumbered on the Eastern Front, Russia urged its Triple Entente ally France to open up a second front in the west. Over forty years earlier in 1870, the Franco-Prussian War had ended the Second French Empire and France had ceded the provinces of Alsace-Lorraine to a unified Germany. Bitterness over that defeat and the determination to retake Alsace-Lorraine made the acceptance of Russia's plea for help an easy choice, so France began full mobilisation on 1 August and, on 3 August, Germany declared war on France. The border between France and Germany was heavily fortified on both sides so, according to the Schlieffen Plan, Germany then invaded neutral Belgium and Luxembourg before moving towards France from the north, leading the United Kingdom to declare war on Germany on 4 August due to their violation of Belgian neutrality.^[14][15] After the German march on Paris was halted in the Battle of the Marne, what became known as the Western Front settled into a battle of attrition, with a trench line that changed little until 1917. On the Eastern Front, the Russian army led a successful campaign against the Austro-Hungarians, but the Germans stopped its invasion of East Prussia in the battles of Tannenberg and the Masurian Lakes. In November 1914, the Ottoman Empire joined the Central Powers, opening fronts in the Caucasus, Mesopotamia and the Sinai. In 1915, Italy joined the Allies and Bulgaria joined the Central Powers; Romania joined the Allies in 1916, as did the United States in 1917.
The Russian government collapsed in March 1917, and a revolution in November followed by a further military defeat brought the Russians to terms with the Central Powers via the Treaty of Brest-Litovsk, which granted the Germans a significant victory. After a stunning German offensive along the Western Front in the spring of 1918, the Allies rallied and drove back the Germans in a series of successful offensives. On 4 November 1918, the Austro-Hungarian empire agreed to an armistice, and Germany, which had its own trouble with revolutionaries, agreed to an armistice on 11 November 1918, ending the war in victory for the Allies.
By the end of the war or soon after, the German Empire, Russian Empire, Austro-Hungarian Empire and the Ottoman Empire ceased to exist. National borders were redrawn, with several independent nations restored or created, and Germany's colonies were parceled out among the victors. During the Paris Peace Conference of 1919, the Big Four (Britain, France, the United States and Italy) imposed their terms in a series of treaties. The League of Nations was formed with the aim of preventing any repetition of such a conflict. This effort failed, and economic depression, renewed nationalism, weakened successor states, and feelings of humiliation (particularly in Germany) eventually contributed to the start of World War II.