Bulgaria entered the WWII after signing the The Tripartite Pact (1 March 1941) which subsequently resulted in a long list1 of war declarations, unilaterally or mutually initiated, against Western Allies countries. However, there is a very interesting period of about two months: September 8th - October 28th 1944 through which Bulgaria de jure was at war with all the countries from both the Allies and the Axis.
What events led to that strange foreign policy situation?
Is there any other known example of a country at war with the "whole world"?
1. List of WWII declarations involving Bulgaria:
1941-04-06 Bulgaria declares war on Yugoslavia.
1941-12-12 Bulgaria declares war on United States, United Kingdom.
1941-12-13 New Zealand, South Africa declare war on Bulgaria.
1941-12-19 Nicaragua declares war on Bulgaria.
1942-01-06 Australia declares war on Bulgaria.
1943-04-02 Bolivia declares war on Bulgaria.
1944-09-05 Soviet Union declares war on Bulgaria.
1944-09-08 Bulgaria declares war on Germany.