80 years ago, on February 21, in the house of chairman of the Democratic Party, Nikola Mushanov, the leaders of the united Bulgarian opposition gathered in an attempt to oppose Bulgaria's accession to the Tripartite Pact signed on September 27, 1940 between Germany, Italy and Japan during World War II (1939-1946). Among them were Atanas Burov, Krastyu Pastuhov, Kimon Georgiev, Grigor Vassilev, Dr. G.M. Dimitrov. Their letter, presented in the palace the same day by Nikola Mushanov, pointed out that the country must remain neutral, but the Tsar refused to listen to them. The Treaty of Accession of Bulgaria to the Tripartite Pact was signed on March 1, 1941.

After a decision of the Council of Ministers of December 29, 2016, the anniversary of the meeting has been marked since 2017 as a Day of Gratitude to those who resisted Nazism in Bulgaria.