List of countries involved in World War II

Axis Powers (signers of the Tripartite Treaty)

• Germany
• Italy
• Japan

co-signers of the Tripartite Treaty

• Bulgaria (March 1st, 1941)
• Hungary (November 20th, 1940)
• Romania (November 23rd, 1940)
• Slovakia⁽¹⁾ (November 24th, 1940)

Countries that were annexed by Axis Powers before the World War II

• Austria (annexed to Germany, "Anschluss", March 13th, 1938)
• Ethiopia (annexed by Italy in 1936, after the Abyssinia crisis[?], independence restored in 1941)

Allied Powers

• Australia
• Brazil
• Canada
• Newfoundland
• New Zealand
• South Africa
• Soviet Union (from June 1941)
• United Kingdom
• United States (from December 1941)

Countries that were at war with Axis Powers before the World War II

• China (at war with Japan since 1931)

Supporters of the Allies

• Argentina
• Bolivia
• Chile
• Colombia
• Costa Rica
• Cuba
• Dominican Republic
• Ecuador
• Egypt⁽²⁾
• El Salvador
• Guatemala
• Haiti
• Honduras
• Iraq
• Lebanon
• Liberia
• Mexico
• Mongolia
• Nicaragua
• Panama
• Paraguay
• Peru
• Saudi Arabia
• Turkey
• Uruguay
• Venezuela

Countries that were attacked, occupied, or switched sides during the war
(Most countries below had declared their neutrality before being assaulted.)

• Algeria
• Albania (occupied by Italy April 7th 1939, by Germany September 26th 1943)
• Belgium (invaded by Germany May 10th 1940)
• Burma
• Czechoslovakia⁽¹⁾ (Bohemia and Moravia occupied by Germany March 15th 1939)
• Denmark (occupied by Germany April 9th 1940, Greenland occupied by USA April 9th 1941)
• Estonia (occupied by the Soviet Union from June 18th 1940, by Germany September 5th 1941, re-annexed by the Soviet Union in 1944)
• Finland (attacked by the Soviet Union November 30th 1939 and June 26th 1941)
• France (surrendered to Germany June 22nd 1940)
• Greece (invaded by Italy October 28th 1940, German occupation from April 6th 1941)
• Iceland (occupied by Great Britain May 10th 1940, by USA from July 1941)
• India
• Iran
• Latvia (occupied by the Soviet Union from June 18th 1940, by Germany June 25th 1941, re-annexed by the Soviet Union in 1944)
• Lithuania (occupied by the Soviet Union from June 18th 1940, by Germany June 22nd 1941, re-annexed by the Soviet Union in 1944)
• Luxembourg (invaded by Germany May 10th 1940)
• Morocco
• The Netherlands (invaded by Germany May 10th 1940)
• New Guinea
• Norway (invaded by Germany April 9th 1940)
• Philippines
• Poland (invaded by Germany and the Soviet Union in September 1939)
• Singapore
• Syria
• Thailand
• Tunisia (Occupied by USA in 1943)
• Yugoslavia⁽³⁾ (German occupation from April 6th 1941)

Countries that remained nominally neutral

• Ireland
• Portugal
• Spain
• Sweden (with exception for the Winter War)
• Switzerland

Notes:

1. Slovakia proclaims independence of Czechoslovakia on March 14th, 1939. Slovakia became a German protectorate. The rest of Czechoslovakia, the provinces Bohemia and Moravia, were occupied by Germany March 15th 1939.
2. Egypt was technically neutral,but Cairo soon became a major military base for the British forces. This was because of a 1936 treaty by which Britain argued it had the right to station troops on Egyptian soil in order to protect the Suez Canal.
3. Yugoslavia began the war as a neutral but Yugoslavia's Regent signed the Tripartite Treaty on March 25th, 1941, and met an anti-Nazi coup d'état when he returned on March 27th. This led to German occupation from April 6th 1941.