The treaty was signed by the Bulgarian prime minister, Hitler’s foreign minister von Ribbentrop, Mussolini’s foreign minister Count Ciano, and Hiroshi Oshima, the Japanese ambassador in Berlin.
Bulgarian joined the Tripartite Pact on this day in 1941, making it an ally of Adolf Hitler and a member of the Axis powers. Bulgaria’s entry into the pact was spurred its pretensions to claim parts of Greek territory (e.g. Thrace, which would allow it access to the Mediterranean Sea). In addition, there existed a fear that the Axis powers would occupy Bulgaria should it refuse to join the Pact. Namely, Bulgaria was blocking their access to Greece, which they wanted to conquer.
The Bulgarian king at the time was Boris III, a member of a German dynasty. Specifically, he was a descendant of the Sachen-Coburg-Gotha dynasty (Prince Albert, the husband of Queen Victoria, came from the same dynasty). In addition, Boris’s mother was the sister of the last Empress of Austria, Zita of Bourbon-Parma, wife of Emperor Charles I (who was later declared a Blessed of the Catholic Church).
The Bulgarian prime minister at the time was Bogdan Filov, who received most of his education in Germany. Apart from him, the treaty was signed by Hitler’s foreign minister von Ribbentrop, Mussolini’s foreign minister Count Ciano, and Hiroshi Oshima, the Japanese ambassador in Berlin.