Tripartite Pact
The Tripartite Pact, also known as the Berlin Pact, was an agreement between Germany, Italy, and Japan signed in Berlin on 27 September 1940 by, respectively, Joachim von Ribbentrop, Galeazzo Ciano and Saburō Kurusu. It was a defensive military alliance that was eventually joined by Hungary (20 November 1940), Romania (23 November 1940), Bulgaria (1 March 1941) and Yugoslavia (25 March 1941) as well as by the German client state of Slovakia (24 November 1940). Yugoslavia's accession provoked a "coup d'état" in Belgrade two days later. Germany, Italy and Hungary responded by invading Yugoslavia. The resulting Italo-German client state, known as the Independent State of Croatia, joined the pact on 15 June 1941.