Countries Involved In World War Two 2021

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World War II started in 1939 and ended in 1945. More than 100 million people from 30 nations participated in the war, resulting in anywhere from 70 million to 85 million civilian and military casualties. World War II was the deadliest war in history.

Leading up to the war, many countries tried remaining neutral. However, as conflict arose, countries gradually began choosing sides. Countries either joined the Axis Powers or the Allied Powers.

Allied Powers

The chief Allied Powers were Great Britain, France, and the United States. At the start of World War II in 1939, the Allies were France, Poland, and the United Kingdom. Days later, the independent Great Britain dominions of Australia, Canada, New Zealand, and South Africa joined. As the war continued, several other countries began joining the Allies. The Allied Powers generally included all 26 original signatories of the Declaration of the United Nations, signed on January 1, 1942.

The countries that were recognized as being Allied Powers in World War II include:

  • Australia
  • Brazil
  • Canada
  • New Zealand
  • South Africa
  • The Soviet Union
  • The United Kingdom
  • The United States of America

Many countries showed their unwavering support for the Allied Powers. These countries were:

Axis Powers

The leading players in the Axis Powers were Japan, the Kingdom of Italy, and Germany. The three main parties that comprised the Axis Powers entered World War II under the Tripartite Treaty. Four other countries ultimately signed the Tripartite Treaty on their terms. Bulgaria co-signed the document on March 1, 1941, and the three European countries of Hungary, Romania, and Slovakia signed the previous year. Hungary signed the treaty on November 20, 1940, and Romania signed three days later. The following day, Slovakia signed the treaty on November 24, 1940.

The other countries that eventually followed suit and walked in the footsteps of the top three Axis Powers were:

Other Countries

World War II had many changes in who supported who, and countries went from neutrality to solid support for one side over the other. Here is a list of countries that were either battlegrounds during the war or places that up and switched their support:

World War II Timeline

Here is a breakdown of some of the most important dates during World War II, accompanied by the countries involved in the events.


September 1, 1939

  • German troops invaded Poland.
  • Hitler was confronted by France and Britain.

September 3, 1939

  • War erupted on this day.

December 17, 1939

  • Germany attacked Uruguay.


May 10, 1940

  • Belgium, Luxembourg, and the Netherlands were attacked by Nazi Germany.
  • Churchill became the ruler of Britain instead of Chamberlain.

May 12, 1940

  • Germans attacked France.

June 10, 1940

  • Italy attacks Britain and France and ultimately invades French borders.

June 14, 1940

  • Germany invades Paris, France.

June 22, 1940

  • Germany and France come together in the city of Compiegne.

November 14, 1940

  • England is attacked by Nazi Germany.


February 15, 1942

  • Singapore is released from British control.
  • Japan takes control of Singapore.

February 19, 1942

  • Concentration camps are opened all over the United States for retaining Japanese Americans.

April 9, 1942

  • United States of America retreats from the Philippines.

May 6, 1942

  • The United States and the Philippines release control to Japan.

June 10, 1942

  • Nazi Germany invades Czechoslovakia.

November 8, 1942

  • British and American troops invade North Africa.


February 1, 1943

  • Germans surrender in Russia.

May 12, 1943

  • War stops in North Africa.

September 3, 1943

  • Allied Powers take control of Italy.

September 8, 1943

  • Italy gives up control.

September 10, 1943

  • Rome is taken over by Nazi Germany.


January 22, 1944

  • American and British military troops arrive on the Anzio coast.

June 4, 1944

  • British and American troops invade Italy.

June 6, 1944

  • The Allied Powers invade Normandy, which is known as D Day to this day.

July 20, 1944

  • Bomb strikes Hitler in Germany.

August 25, 1944

  • Paris becomes free from outside control.

October 13, 1944

  • The Allied Powers let go of Athens, Greece.

October 20, 1944

  • The Philippines are invaded by America.

December 16, 1944

  • The Battle of the Bulge is calculated by Germany.


February 11, 1945

  • A bit of reorganization takes place among countries.

April 28, 1945

  • Mussolini is murdered during an invasion.

May 1, 1945

  • Hitler dies by suicide.
  • Germany is taken over by other troops.

May 8, 1945

  • V-E Day is declared by the Allied troops of World War II.

July 28, 1945

  • The Potsdam Conference takes place.

August 6, 1945

  • The United States uses nuclear weapons against Japan by dropping a bomb on the Japanese island of Hiroshima.

August 8, 1945

  • Russia invades Japan, too.

August 9, 1945

  • The United States drops another bomb on the Japanese city of Nagasaki.

September 2, 1945

  • V-J Day marks the end of World War II.

Countries Involved In World War Two 2021

Rank Country 2021 Population
United States332,915,073
United Kingdom68,207,116
South Africa60,041,994
New Zealand4,860,643

Countries Involved In World War Two 2021