The Tripartite Pact, also known as the Berlin Pact, was an agreement between Joachim von Ribbentrop for Germany; Galeazzo Ciano for Italy; and Saburō Kurusu for Japan. The Pact was signed in the presence of Adolf Hitler in Berlin on September 27, 1940.
This Axis was eventually joined by Hungary on November 20, 1940, Romania on November 23, 1940, Bulgaria (March 1, 1941, and Yugoslavia March 25, 1941. The German client state of Slovakia joined on November 25, 1940.
The Axis was only ever a loose defensive alliance, more of an aspiration against the United States. Its defensive clauses were never invoked, and signing the agreement did not oblige its signatories to fight a common war. Yet it inspired Reichklanzler Adolf Hitler to declare war on the United States following the Japanese attack on Pearl Harbor, virtually ensuring his doom.
Author of the World War II Multimedia Database