The First World War (1914-18) was waged between the Central Powers (Germany, Austria-Hungary, Turkey, Bulgaria) and the Allied and Associated Powers led by France, UK and the British Empire, Russia and—later—the USA. The Allied side also included Belgium, Serbia, Montenegro, Japan, Portugal, Italy, Romania and eventually Liberia, China, Brazil, and Guatemala.
It began with a declaration of war by Austria upon Serbia on 28 July 1914; it ended at 11am on 11 November 1918 when the terms of the Armistice granted to the defeated German army came into effect. The greater part of the actual fighting was by land armies. Combatant armies at the outset totalled over 16 million. At the end of the war, the total mobilised strength in service was nearly 26 million. From first to last, Germany mobilised 11 million men; the UK and British Empire nearly 9 million. Nearly 8 million combatants of all nations were killed including over 2 million Germans, 1.7 million Russians, 1.3 million French, 1,2 million Austro-Hungarians and over 1 million from the British Empire. As an immediate or direct result of the war, nearly £40,000 million of debt or expenditure was incurred.
Russia withdrew from the war on 15 December 1917, following the Bolshevik revolution. War was formally ended by the treaties of Versailles which Germany signed on 28 June 1919 and which established the League of Nations.