World War I
WW1 TitlePicture For Wikipedia Article
Alternate ww1 alliances
Clockwise from top: Trenches on the Western Front; a British Mark IV Tank crossing a trench; Royal Navy battleship HMS Irresistible sinking after striking a mine at the Battle of the Dardanelles; a Vickers machine gun crew with gas masks, and German Albatros D.III biplanes.
Alliances of the war. Green: Allies and their colonies. Orange: Central Powers and their colonies.
Date 28 July 1914 - 7 June 1918 (3 years, 10 months, 10 days)
Location Europe, Africa, the Middle East, the Pacific Islands, China, Indian Ocean, and off the coast of South and North America
Result Central Powers victory
Allied Powers
Flag of the United Kingdom British Empire
Flag of France France
Flag of Russia Russia (1914-1917)
Flag of Serbia (1882-1918) Serbia
Flag of Montenegro (1905-1918 & 1941-1944) Montenegro
Flag of Belgium Belgium
Flag of Japan Japan
Flag of Portugal Portugal (1916-1918)
Flag of Romania Romania (1916-1918)
Hellenic Kingdom Flag 1935 Greece (1916-1918)
Central Powers
Flag of the German Empire Germany
Flag of Austria-Hungary (1869-1918) Austria-Hungary
Flag of the Ottoman Empire Ottoman Empire
Flag of Italy (1861-1946) Italy
Flag of the Netherlands Netherlands
Flag of Bulgaria Bulgaria (1915-1918)
Commanders and leaders
Main Allied leaders
Flag of the United Kingdom H. H. Asquith
Flag of the United Kingdom David Lloyd George
Flag of France Georges Clemenceau
Flag of France Raymond Ponicaré
Flag of Belgium Albert I
Flag of Belgium Charles de Broqueville
Flag of Japan Yoshihito
Flag of RussiaNicholas II
Flag of Serbia (1882-1918) Peter I
Flag of Romania Ferdinand I
Hellenic Kingdom Flag 1935 Eleftherios Venizelos
Main Central Powers leaders
Flag of the German EmpireWilhelm II
Flag of Austria-Hungary (1869-1918)Franz Joseph I
Flag of Austria-Hungary (1869-1918)Karl I
Flag of the Ottoman EmpireMehmed V
Flag of Italy (1861-1946)Antonio Salandra
Flag of Italy (1861-1946)Victor Emmanuel III
Flag of the NetherlandsPieter Cort van der Linden
Flag of Bulgaria Ferdinand I
Allied Powers
Flag of Russia 12,000,000
Flag of the United Kingdom 8,841,541
Flag of France 8,660,000
Flag of Romania 1,234,000
Flag of Japan 800,000
Flag of Serbia (1882-1918) 707,343
Flag of Belgium 380,000
Hellenic Kingdom Flag 1935 250,000
Flag of Portugal 100,000
Flag of Montenegro (1905-1918 & 1941-1944) 50,000
Total: 33,022,884
Central Powers
Flag of the German Empire 13,250,000
Flag of Austria-Hungary (1869-1918) 7,800,000
Flag of Italy (1861-1946) 5,615,140
Flag of the Ottoman Empire 2,998,321
Flag of Bulgaria 1,200,000
Flag of the Netherlands 500,000
Total: 31,363,461
Casualties and losses
Allied Powers
Military dead: 5,129,000
Military wounded: 13,031,500
Military missing: 4,761,000
Total: 22,921,500 KIA,WIA or MIA
Central Powers
Military dead: 4,872,000
Military wounded: 9,105,000
Military missing: 4,299,000
Total: 18,276,000

World War I (WWI or WW1), also known as the First World War, or the Great War, was a global war originating in Europe that lasted from 28 July 1914 to 7 June 1918. More than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. 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.

The war drew in all the world's economic great powers aside from the United States, 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, Austria-Hungary and Italy. These alliances were reorganised and expanded as more nations entered the war: Japan joined the Allies, while the Netherlands, 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, 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.

On 28 July, the Austro-Hungarians declared war on Serbia. As Russia mobilised in support of Serbia, Germany and the Netherlands invaded neutral Belgium and Luxembourg before moving towards France, leading the United Kingdom to declare war on both nations. After the German-Dutch march on Paris was halted, 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 was successful against the Austro-Hungarians, but the Germans stopped its invasion of East Prussia. In November 1914, the Ottoman Empire joined the Central Powers, opening fronts in the Caucasus, Mesopotamia and the Sinai. In 1915, Bulgaria joined the Central Powers; Romania and Greece joined the Allies in 1916.

The Russian government collapsed in March 1917, and a revolution in October 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 Central Powers offensive along the Western Front in the spring of 1918, the Allies crumbled and retreated. On 7 June, the Allies agreed to an armistice, ending the war in victory for the Central Powers.

By the end of the war or soon after, the Russian Empire, Austro-Hungarian Empire and the Ottoman Empire ceased to exist. National borders were redrawn, with several independent nations restored or created, and French and British colonies were parceled out among the winners. During the Vienna Peace Conference of 1919, the Big Four (Germany, Austria-Hungary, Italy and the Netherlands) 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 manifest destiny (particularly in Germany) eventually contributed to World War II.