War Declaration Opponent (s) Date of declaration Votes President Result Senate House War of 1812 Declaration of War upon the U.K. United Kingdom June 18, 1812 19 -- 13 79 -- 49 James Madison Treaty of Ghent (December 24, 1814) Mexican -- American War "An Act providing for the Prosecution of the existing War between the United States and the Republic of Mexico. '' Mexico May 13, 1846 40 -- 2 173 -- 14 James K. Polk Treaty of Guadalupe Hidalgo (February 2, 1848) Spanish -- American War Declaration of War upon Spain Spain April 25, 1898 42 -- 35 310 -- 6 William McKinley Treaty of Paris (December 10, 1898) World War I Declaration of War upon Germany Germany April 6, 1917 82 -- 6 373 -- 50 Woodrow Wilson Treaty of Berlin (August 25, 1921) Declaration of War upon Austria - Hungary Austria - Hungary December 7, 1917 74 -- 0 365 -- 1 1921 U.S. -- Austrian Peace Treaty (August 24, 1921), 1921 U.S. - Hungarian Peace Treaty (August 29, 1921) World War II Declaration of War upon Japan Japan December 8, 1941 82 -- 0 388 -- 1 Franklin D. Roosevelt V-J Day, Japanese Instrument of Surrender (September 2, 1945), Treaty of San Francisco (September 8, 1951) Declaration of War upon Germany Germany December 11, 1941 88 -- 0 393 -- 0 V-E Day, German Instrument of Surrender (May 8, 1945), Treaty on the Final Settlement with Respect to Germany (September 12, 1990), Treaty of Vienna with Austria (May 15, 1955) Declaration of War upon Italy Italy 90 -- 0 399 -- 0 Paris Peace Treaty (February 10, 1947) Declaration of War upon Bulgaria Bulgaria June 5, 1942 73 -- 0 357 -- 0 Declaration of War upon Hungary Hungary 360 -- 0 Declaration of War upon Romania Romania 361 -- 0
when is the last time the us declared war
June 5, 1942