The pact was rounded in September 1940 by the signation of the Tripartite Treaty between the Third Reich (Germany), the Empire of Japan, and the Kingdom of Italy. Several other nations, had adhered to either the 1936 or the 1940 pact.
Three nations are considered the Axis Powers:
After a civil war in 1944, Benito Mussolini was depossed and assassinated. The Third Reich invaded Italy and treated it as occupied territory up to 1948, when souveraignity was restored, and Power status was again granted.
Short after the beginning of the German Civil War, the Third Reich stopped any functional activity as Axis power. In 1982, Japan and Italy agreed to resign from the Axis, seeking better understanding with the United Kingdom and the United States.
While some Axis allies were full sovereign nations that opted in for an alliance with Germany, Italy, and Japan, some other Axis allies were just puppet regimes from any of the Axis powers.