World War 1 began in 1914 after the assassination of Archduke Franz Ferdinand of Austria-Hungary by Serbian nationalists. Major powers formed alliances that split Europe into the Allied and Central Powers. The US initially remained neutral but was drawn into the war in 1917 after Germany resumed unrestricted submarine warfare. Over 2 million American troops deployed to Europe under General Pershing. Key US battles in 1918 helped turn the tide in favor of the Allies. An armistice in November 1918 ended the war. The resulting Treaty of Versailles redrew borders and imposed punitive terms on Germany.