The outbreak of the First World War

The deeper causes were rivalry among the great powers over colonies, markets and spheres of influence, the arms race, and the division of Europe into two blocs: the Triple Alliance (Germany, Austria-Hungary, Italy) and the Entente (Britain, France, Russia). The trigger was the assassination in Sarajevo on 28 June 1914 (new style) of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, by the Bosnian Serb nationalist Gavrilo Princip. Austria-Hungary sent Serbia an ultimatum and declared war on 28 July; through the chain of alliances Germany declared war on Russia (1 August) and France (3 August), and after Belgian neutrality was violated Britain entered on 4 August. Germany’s Schlieffen Plan aimed at a quick defeat of France through Belgium, but at the Battle of the Marne (6–12 September 1914) French and British forces stopped the Germans and the front turned into trench warfare. Russia attacked in East Prussia and Galicia; in 1915 the Central Powers gained the upper hand in the east and the Russian army withdrew. The Ottoman Empire entered the war on Germany’s side at the end of October 1914; the Entente attacked the Dardanelles from the sea in February–March 1915 and landed troops on the Gallipoli peninsula in April, but the operation failed and the troops were withdrawn in January 1916. Italy joined the Entente on 23 May 1915, and Bulgaria joined the Central Powers in October. Japan declared war on Germany on 23 August 1914. New weapons appeared: submarines and poison gas (Ypres, April 1915).