World War II had campaigns occurring in Europe.
The Balkan Campaign of World War II began with the Italian invasion of Greece on 28 October 1940 . World War II . Supplied by the Soviet Union , from late 1939 to early 1941 , in a series of campaigns and treaties , Germany conquered or controlled much of continental Europe , and formed the Axis alliance with Italy and Japan . The war continued primarily between the European Axis powers and the coalition of the United Kingdom and the British Commonwealth , with campaigns including the North Africa and East Africa campaigns , the aerial Battle of Britain , the Blitz bombing campaign , the Balkan Campaign as well as the long-running Battle of the Atlantic . In December 1941 , Japan attacked the United States and European colonies in the Pacific Ocean , and quickly conquered much of the Western Pacific .