Military history of Bulgaria during World War II

The military history of Bulgaria during World War II encompasses an initial period of neutrality until 1 March 1941, a period of alliance with the Axis Powers until 9 September 1944 (on 8 September, the Red Army entered Bulgaria) and a period of alignment with the Allies in the final year of the war. Bulgaria functioned as a constitutional monarchy during most of World War II. Tsar Boris III (reigned 1918-1943) ruled with a Prime Minister and a Parliament.