United States Declares War on Germany (1917)
On April 6, 1917, the United States declared war on Germany and officially entered World War I. Prior to this, the United States had adopted a policy of isolationism, preferring to avoid conflict. Even after a German U-boat sank the passenger ship Lusitania in 1915, killing most of the 128 American citizens on board, the United States refused to fight. Rather than declaring war, President Woodrow Wilson demanded an end to attacks on passenger ships, and Germany complied.
In January of 1917, a telegram from Germany to Mexico was intercepted and decoded. The telegram proposed that should the United States enter the war, Germany would ally with Mexico against the U.S. In return, Germany would assist Mexico in reclaiming Texas, Arizona, and New Mexico from the United States. At the same time, Germany decided to resume unrestricted submarine warfare. This telegram, combined with the sinking of seven U.S. merchant ships, moved President Wilson to action.
After an impassioned speech by President Wilson on April 2, the United States officially declared war on Germany and entered World War I on April 6, 1917. Though the U.S. only had a small army at the time, it drafted four million men, and by summer 1918 was sending 10,000 fresh soldiers to France every day. The United States became a driving force for the Allied Powers and Germany surrendered on Armistice Day, November 11, 1918.