World War II involved Japan, Germany, and Italy.
Axis powers . The Axis grew out of the diplomatic efforts of Germany , Italy and Japan to secure their own specific expansionist interests in the mid-1930s . World War II . It involved the vast majority of the world 's countries -- including all of the great powers -- eventually forming two opposing military alliances : the Allies and the Axis . 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 . In 1943 , with a series of German defeats on the Eastern Front , the Allied invasion of Sicily and the Allied invasion of Italy which brought about Italian surrender , and Allied victories in the Pacific , the Axis lost the initiative and undertook strategic retreat on all fronts .