Timeline of Declarations of War During World War II
The declarations of war during the Second World War involved many countries and occurred at different times throughout the conflict. Below is a list of countries and their respective declarations of war. Note that the dates refer to when countries declared war on another state, which may vary depending on alliances, invasions, and shifting allegiances during the war.
1939
- Germany: Declared war on Poland on September 1.
- United Kingdom: Declared war on Germany on September 3.
- France: Declared war on Germany on September 3.
- Australia: Declared war on Germany on September 3.
- New Zealand: Declared war on Germany on September 3.
- South Africa: Declared war on Germany on September 6.
- Canada: Declared war on Germany on September 10.
- Soviet Union: Invaded Poland on September 17, though not a formal declaration of war.
1940
- Italy: Declared war on France and the United Kingdom on June 10.
- Germany: Declared war on Norway and Denmark on April 9 (through invasion).
- United Kingdom and France: Declared war on Italy on June 10.
1941
- Germany: Declared war on the Soviet Union on June 22.
- Italy: Declared war on the Soviet Union on June 22.
- Japan: Declared war on the United States and the British Empire on December 7-8.
- United States: Declared war on Japan on December 8.
- Germany: Declared war on the United States on December 11.
- Italy: Declared war on the United States on December 11.
- United States: Declared war on Germany and Italy on December 11.
1942
- Brazil: Declared war on Germany and Italy on August 22.
- Mexico: Declared war on Germany, Italy, and Japan on May 22.
1943
- Italy: Declared war on Germany on October 13, after the fall of Mussolini and the armistice with the Allies.
1944
- Declarations were fewer during this time as the war had already spread globally.
Additional Notes
Some countries declared war as part of aligning with the Allies or Axis, and others due to invasions or political pressures. Not all declarations were formal; some actions were effectively declarations of war without formal announcements. For example:
- The Soviet Union was attacked by Germany in 1941, leading to immediate war.
- Countries in Eastern Europe were often invaded without formal declarations.
