The Joint Resolution below was passed by Congress on April 6, 1917. Therefore be it resolved by the Senate and the House of Representatives of the
United States of America in Congress assembled, that the state of war between the
United States and the Imperial German Government which has thus been thrust
upon the United States is hereby formally declared, and that the President be, and
he is hereby, authorized and directed to employ the entire naval and military forces of
the United States and the resources of the Government to carry on war against the
Imperial German Government.
Which event led to this Joint Resolution?