This is LONG!
During the First World War the Alliances were:
"Allies" (Triple Entente):
*Belgium (including Belgian colonial forces)
*British Empire
**Great Britain
*The Dominions of the British Empire:
**Australia
**Canada
**New Zealand
**Newfoundland (not part of Canada at the time)
**South Africa
*British Crown Colonies, including:
**The Indian Empire (later India, Pakistan and Bangladesh)
*Sri Lanka
*Nepal
*Myanmar and
*British Malaya
*France (including French colonial forces)
*Italy (from 23 May 1915)
*Romania (from 27 August 1916)
*Russian Empire (until 1917)
*Serbia
*United States (from 7 April 1917)
*Greece (from 1917)
*Montenegro (until 1916)
*Portugal (from March 1916)
as well as:
Andorra
First Republic of Armenia
Brazil
China (from 1917)
Costa Rica
Czechoslovak Legions
Cuba
Guatemala
Haiti
Honduras
Japan
Liberia
Nicaragua
Panama
San Marino
Siam (now Thailand)
The Central Powers were:
*Germany
*Austria-Hungary
*The Ottoman Empire
*Bulgaria
During the Second World War the Allies were (dates are shown for when they entered the war against the Axis):
Following the German invasion of Poland
Poland: 1 September 1939
United Kingdom: 3 September 1939
France: 3 September 1939
Australia: 3 September 1939
New Zealand: 3 September 1939
The Indian Empire: 4 September 1939
Nepal: 4 September 1939
Newfoundland: 4 September 1939
Tonga: 4 September 1939
South Africa: 6 September 1939
Canada: 10 September 1939
After the end of the Phony War
Denmark: 9 April 1940
Norway: 9 April 1940
Belgium: 10 May 1940
Luxembourg: 10 May 1940
Netherlands: 10 May 1940
Free France: 18 June 1940
Greece: 28 October 1940
Kingdom of Yugoslavia: 6 April 1941
Soviet Union: 22 June 1941
Tannu Tuva: 25 June 1941
After the attack on Pearl Harbor
Panama: 7 December 1941
Philippines: 7 December 1941
Costa Rica: 8 December 1941
Dominican Republic: 8 December 1941
El Salvador: 8 December 1941
Haiti: 8 December 1941
Honduras: 8 December 1941
Nicaragua: 8 December 1941
United States of America: 8 December 1941
Republic of China: 9 December 1941
Guatemala: 9 December 1941
Cuba: 9 December 1941
Czechoslovakia: 16 December 1941
Mexico: 22 May 1942
Brazil: 22 August 1942
Ethiopia: 14 December 1942
Iraq 1943: 17 January
Bolivia: 7 April 1943
Iran 1943: 9 September
Italy: 13 October 1943
Colombia: 26 November 1943
Liberia: 27 January 1944
After D-Day
Romania: 25 August 1944, (formerly a member of the Axis powers)
Bulgaria: 8 September 1944, (formerly a member of the Axis)
San Marino: 21 September 1944
Albania: 26 October 1944
Hungary: 20 January 1945, (formerly a member of the Axis)
Bahawalpur: 2 February 1945
Ecuador: 2 February 1945
Paraguay: 7 February 1945
Peru: 12 February 1945
Uruguay: 15 February 1945
Venezuela: 15 February 1945
Turkey: 23 February 1945
Lebanon: 27 February 1945
Saudi Arabia: 1945 March
Argentina: 27 March 1945
Chile: 11 April 1945
People's Republic of Mongolia: 9 August 1945
The Axis powers were:
*Nazi Germany
*Italy
*Japan
*Thailand
*Hungary
*Bulgaria
*Romania (until 23 August 1944)
*Croatia
*Vichy France
*Finland
The Following Nations were occupied by the Axis powers:
*Albania
*Austria (annexed during the Anschluss)
*Belgium
*Denmark
*Ethiopia
*"Lokot Republic" the occupied areas of Russia
*Luxembourg
*Manchuria (a Japanese client state)
*Provisional Government of Free India (which was a rebel government against the Japanese in the occupied areas of British India)
*Vichy France