July 28, 1914
A month after the assassination in Sarajevo on June 28 of the heir to the throne of the Austro-Hungarian Empire, Austria-Hungary declared war on Serbia, and the First World War began. Germany declared war on Russia on August 1, on France on August 3 and on Belgium the next day. Great Britain declared war on Germany on August 4, and on August 6 Austria-Hungary declared war on Russia. Through an alliance with Great Britain, Japan declared war on Germany on August 13, and in late October, 1914, Turkey entered the war in support of Germany, provoking declarations of war from Russia, on November 2, and from Great Britain and France on November 5.