The First World War began on July 28, 1914, when Austria-Hungary formally declared war on Serbia. While tensions had been rising across Europe for many years prior, it was the Serbian assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914 that sparked the declaration.
The main players at the start of the war were the Allies (or Entente Powers), made up of Russia, France and Britain, and the Central Powers, including Germany, Austria-Hungary and Turkey. The United States and Italy joined the Allies in subsequent years. During the course of World War I, over 8 million people died, and the countries involved experienced economic and physical devastation on an enormous scale. The First World War did not end until Germany surrendered on Nov. 11, 1918.