The Axis powers (German: Achsenmächte; Italian: Potenze dell'Asse; Japanese: 枢軸国 Sūjikukoku), also known as "Rome–Berlin–Tokyo Axis" (also nicknamed with the Italian name "Roberto", from the initials of "ROma", "BERlin" and "TOkyo"), were the nations that fought in World War II against the Allies. The Axis powers agreed on their opposition to the Allies, but did not completely coordinate their activity.
The Axis grew out of the diplomatic efforts of Germany, Italy, and Japan to secure their own specific expansionist interests in the mid-1930s. The first step was the treaty signed by Germany and Italy in October 1936. Benito Mussolini declared on 1 November that all other European countries would from then on rotate on the Rome–Berlin axis, thus creating the term "Axis". The almost simultaneous second step was the signing in November 1936 of the Anti-Comintern Pact, an anti-communist treaty between Germany and Japan. Italy joined the Pact in 1937. The "Rome–Berlin Axis" became a military alliance in 1939 under the so-called "Pact of Steel", with the Tripartite Pact of 1940 leading to the integration of the military aims of Germany, Italy and Japan.
At its zenith during World War II, the Axis presided over territories that occupied large parts of Europe, North Africa, and East Asia. There were no three-way summit meetings and cooperation and coordination was minimal, with slightly more between Germany and Italy. The war ended in 1945 with the defeat of the Axis powers and the dissolution of their alliance. As in the case of the Allies, membership of the Axis was fluid, with some nations switching sides or changing their degree of military involvement over the course of the war.