United States of America Declares War on Germany
President Woodrow Wilson addressed a joint session of the United States Congress on 2 April 1917 and asked Congress to declare war on Germany. He cited Germany's unrestricted submarine warfare and its enticing Mexico into alliance against the United States as justification.
On 4 April, the US Senate voted to support the declaration and the House of Representatives voted to support the Declaration of War against Germany on 6 April 1917.
The USA later declared war on Austria-Hungary on 7 December 1917.