Outbreak of the Great War
World War I in eastern Europe and the Russian Revolution (3 August 1914)
Historical Map of Russia
The June 28 assassination of Archduke Franz Ferdinand of Austria-Hungary by a Bosnian Serb triggered a series of political crises across Europe. On July 28, Austria-Hungary declared war on Serbia, a country protected by Russian guarantees. Russia responded by mobilizing its armies, which in turn led to war with Austria-Hungary's ally Germany. A few days later, France and then Britain joined the war on the side of Russia.