All the leading countries of Europe were drawn into the war. It began when the archduke of Austria- Hungary, Franz Ferdinand, and his wife, Sophia, were assassinated in Bosnia in June 1914. The Austro-Hungarian government claimed that the Bosnian-Serb assassin had the clandestine support of the Serbian government, which the government in Belgrade denied.
How a Terrible War Began and Played Out
Ultimatums and counter-ultimatums soon set in motion a series of European military alliances among the Great Powers. In late July and early August, the now-warring parties issued formal declarations of war. Imperial Germany, the Turkish Empire, and Bulgaria supported Austria-Hungary. Imperial Russia supported Serbia, which soon brought in France and Great Britain because these countries were aligned with the czarist government in St. Petersburg. Italy entered the war in 1915 on the side of the British and the French.