Woodrow Wilson strongly opposed imperialism and wanted honesty and unselfishness in international affairs. Tensions in Europe were rising in the early 1900s due to militarism, alliances, imperialism, and nationalism. The assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian nationalist triggered World War I. Though the U.S. remained neutral at first, events like the sinking of the Lusitania and attacks on American ships drew the country into the war on the side of the Allies in 1917.