When did the United States declare war?

There have been five formally declared wars in US history:
  1. The War of 1812 with the United Kingdom - Declared 6/18/1812
  2. The Mexican-American War - Declared 5/13/1846
  3. The Spanish-American War - Declared 4/25/1898
  4. WW1 - Declared against Germany 4/6/1917 and Austria-Hungary 12/07/1917
  5. WW2 - Declared against Japan 12/8/1941; against Germany & Italy 12/11/1941; Bulgaria, Hungary, and Romania 6/5/1942

All other military actions were either informal interventions, or policing actions sanctioned in part or whole by Congress. These include:

  1. The Quasi-War (France) - 07/09/1798
  2. First Barbary War (Tripoli) - 02/06/1802
  3. Second Barbary War (Algiers) - 05/10/1815
  4. African Slave Trade Ban - 1819-1823
  5. Engagement of the Paraguayan Navy - 1859
  6. Engagement with Russian forces during the Russian civil War - 1917-1923
  7. Korean War - 07/07/1950
  8. Lebanon Crisis of 1958 - Operation Blue Bat - 07/15/1958
  9. Vietnam War - 08/07/1964
  10. Peace-Keeping operations during the Bosnian War - 03/19/1978
  11. Lebanon Peace-Keeping Coalition - 09/29/1983
  12. Operation Desert Storm - 01/12/1991
  13. Operation Enduring Freedom - 09/14/2001 - Ongoing
  14. Operation Iraqi Freedom - 03/03/2003 - Ongoing
  15. Peace-Keeping Operations during the Second Liberian Civil War - 08/01/2003
  16. The United Nations Stabilization Mission in Haiti - 02/29/2004

Additionally, there are a vast number of military actions and engagements that have taken place as a result of the President exercising his power as the Command-in-Chief.
There have been five formally declared wars in US history:
  1. The War of 1812 with the United Kingdom - Declared 6/18/1812
  2. The Mexican-American War - Declared 5/13/1846
  3. The Spanish-American War - Declared 4/25/1898
  4. WW1 - Declared against Germany 4/6/1917 and Austria-Hungary 12/07/1917
  5. WW2 - Declared against Japan 12/8/1941; against Germany & Italy 12/11/1941; Bulgaria, Hungary, and Romania 6/5/1942

All other military actions were either informal interventions, or policing actions sanctioned in part or whole by Congress. These include:

  1. The Quasi-War (France) - 07/09/1798
  2. First Barbary War (Tripoli) - 02/06/1802
  3. Second Barbary War (Algiers) - 05/10/1815
  4. African Slave Trade Ban - 1819-1823
  5. Engagement of the Paraguayan Navy - 1859
  6. Engagement with Russian forces during the Russian civil War - 1917-1923
  7. Korean War - 07/07/1950
  8. Lebanon Crisis of 1958 - Operation Blue Bat - 07/15/1958
  9. Vietnam War - 08/07/1964
  10. Peace-Keeping operations during the Bosnian War - 03/19/1978
  11. Lebanon Peace-Keeping Coalition - 09/29/1983
  12. Operation Desert Storm - 01/12/1991
  13. Operation Enduring Freedom - 09/14/2001 - Ongoing
  14. Operation Iraqi Freedom - 03/03/2003 - Ongoing
  15. Peace-Keeping Operations during the Second Liberian Civil War - 08/01/2003
  16. The United Nations Stabilization Mission in Haiti - 02/29/2004

Additionally, there are a vast number of military actions and engagements that have taken place as a result of the President exercising his power as the Command-in-Chief.