The First World War was a global war involving nearly all the world's nations from 1914 to 1918. It was caused by overlapping alliances that drew the major powers of Europe into war after the assassination of Archduke Franz Ferdinand of Austria-Hungary. While the U.S. initially remained neutral, American involvement was prompted by Germany's unrestricted submarine warfare and the intercepted Zimmerman Telegram. America then provided significant financial and military support to help the Allies defeat the Central Powers. The war had lasting social and political impacts on the United States through the expanded roles of women and African Americans and increased policies enforcing patriotism.