World war ii has 2 different meanings across 2 categories:
a war between the Allies (Australia, Belgium, Bolivia, Brazil, Canada, China, Colombia, Costa Rica, Cuba, Czechoslovakia, Dominican Republic, El Salvador, Ethiopia, France, Greece, Guatemala, Haiti, Honduras, India, Iran, Iraq, Luxembourg, Mexico, Netherlands, New Zealand, Nicaragua, Norway, Panama, Philippines, Poland, South Africa, United Kingdom, United States, USSR, Yugoslavia) and the Axis (Albania, Bulgaria, Finland, Germany, Hungary, Italy, Japan, Rumania, Slovakia, Thailand) from 1939 to 1945
The war from 1939 to 1945 of the Allied forces, including the United Kingdom, the Soviet Union, the United States, France, and China, against the Axis Powers, including Germany, Italy, and Japan.