War Entry Dates

 

Against the Allies
  Date
Germany 1 September, 1939
Italy 1 June, 1940
Hungary 10 April, 1941
Bulgaria 24 April, 1941
Romania 22 June, 1941
Finland 25 June, 1941
Slovakia 1 December, 1941
Japan 7 December, 1941
Croatia 14 December, 1941
Albania 17 December, 1941
Thailand 25 January, 1942

 

Against the Axis
  Date
Poland 1 September, 1939
United Kingdom 3 September, 1939
France 3 September, 1939
Australia 3 September, 1939
India 3 September, 1939
New Zealand 3 September, 1939
South Africa 3 September, 1939
Canada 10 September, 1939
Denmark 9 April, 1940
Norway 9 April, 1940
Belgium 10 May, 1940
Luxembourg 10 May, 1940
Netherlands 10 May, 1940
Greece 28 October, 1940
Yugoslavia 6 April, 1941
U.S.S.R. 22 June, 1941
United States 7 December, 1941
Panama 7 December, 1941
Philippines 7 December, 1941
Costa Rica 8 December, 1941
Dominican Republic 8 December, 1941
Guatemala 9 December, 1941
Honduras 8 December, 1941
Nicaragua 8 December, 1941
China 9 December, 1941
Brazil 2 May, 1942
Mexico 22 May, 1942
Ethiopia 1 December, 1942
Iraq 16 January, 1943
Bolivia 7 April, 1943
Iran 9 September, 1943
Italy 13 October, 1943
Colombia 26 November, 1943
Liberia 27 January, 1944
Romania 24 August, 1944
Bulgaria 8 September, 1944
Finland 15 September, 1944
Hungary 20 January, 1945
Ecuador 2 February, 1945
Paraguay 8 February, 1945
Peru 11 February, 1945
Chile 12 February, 1945
Venezuela 14 February, 1945
Uruguay 22 February, 1945
Turkey 23 February, 1945
Egypt 26 February, 1945
Syria 26 February, 1945
Lebanon 7 February, 1945
Saudi Arabia 1 March, 1945
Argentina 27 March, 1945
Mongolia 9 August, 1945

 

Notes:

(1) China begins fighting Japanese on 7 July, 1937.

(2) Italy, Finland, Romania, Bulgaria and Hungary switched sides between 1943-45.

Source: The International History Project.