The Axis powers, originally called the Rome–Berlin Axis, was a military coalition that initiated World War II and fought against the Allies. Its principal members were Nazi Germany, the Kingdom of Italy, and the Empire of Japan. The Axis were united in their opposition to the Allies, but otherwise lacked comparable coordination and ideological cohesion. Particularly within Europe, the use of the term "the Axis" primarily refers to the alliance between Italy and Germany, though outside Europe it is normally understood as including Japan.