World War 1

World War 1 or the First World War (28 July 1914 — 11 November 1918), also known as the Great War, was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers. Fighting took place mainly in Europe and the Middle East, as well as in parts of Africa and the Asia-Pacific, and in Europe was characterised by trench warfare; the widespread use of artillery, machine guns, and chemical weapons (gas); and the introductions of tanks and aircraft. World War I was one of the deadliest conflicts in history, resulting in an estimated 10 million military dead and more than 20 million wounded, plus some 10 million civilian dead from causes including genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.

The causes of World War I included the rise of Germany and decline of the Ottoman Empire, which disturbed the long-standing balance of power in Europe, and rising economic competition between nations driven by industrialisation and imperialism. Growing tensions between the great powers and in the Balkans reached a breaking point on 28 June 1914, when Gavrilo Princip, a Bosnian Serb, assassinated the heir to the Austro-Hungarian throne. Austria-Hungary blamed Serbia, and declared war on 28 July. After Russia mobilised in Serbia's defence, Germany declared war on Russia and France, who had an alliance. The United Kingdom entered after Germany invaded Belgium, and the Ottomans joined the Central Powers in November. Germany's strategy in 1914 was to quickly defeat France then transfer its forces to the east, but its advance was halted in September, and by the end of the year the Western Front consisted of a near-continuous line of trenches from the English Channel to Switzerland. The Eastern Front was more dynamic, but neither side gained a decisive advantage, despite costly offensives. Italy, Bulgaria, Romania, Greece and others joined in from 1915 onward.

Major battles, including at Verdun, the Somme, and Passchendaele, failed to break the stalemate on the Western Front. In April 1917, the United States joined the Allies after Germany resumed unrestricted submarine warfare against Atlantic shipping. Later that year, the Bolsheviks seized power in Russia in the October Revolution; Soviet Russia signed an armistice with the Central Powers in December, followed by a separate peace in March 1918. That month, Germany launched a spring offensive in the west, which despite initial successes left the German Army exhausted and demoralised. The Allied Hundred Days Offensive beginning in August 1918 caused a collapse of the German front line. Following the Vardar Offensive, Bulgaria signed an armistice in late September. By early November, the Ottoman Empire and Austria-Hungary had each signed armistices with the Allies, leaving Germany isolated. Facing a revolution at home, Kaiser Wilhelm II abdicated on 9 November, and the war ended with the Armistice of 11 November 1918.

The Paris Peace Conference of 1919—1920 imposed settlements on the defeated powers, most notably the Treaty of Versailles, by which Germany lost significant territories, was disarmed, and was required to pay large war reparations to the Allies. The dissolution of the Russian, German, Austro-Hungarian, and Ottoman Empires redrew national boundaries and resulted in the creation of new independent states, including Poland, Finland, the Baltic states, Czechoslovakia, and Yugoslavia. The League of Nations was established to maintain world peace, but its failure to manage instability during the interwar period contributed to the outbreak of World War II in 1939.

Before World War II, the events of 1914—1918 were generally known as the Great War or simply the World War 1. In August 1914, the magazine The Independent wrote "This is the Great War. It names itself." In October 1914, the Canadian magazine Maclean's similarly wrote, "Some wars name themselves. This is the Great War. Contemporary Europeans also referred to it as "the war to end war" and it was also described as "the war to end all wars" due to their perception of its unparalleled scale, devastation, and loss of life. The first recorded use of the term First World War was in September 1914 by German biologist and philosopher Ernst Haeckel who stated, "There is no doubt that the course and character of the feared 'European War' ... will become the first world war in the full sense of the word.