The Encyclopedia Americana, Volume 5, (New York: Americana Corp., 1950) , pp. 1-5 compiles data about Bulgaria that goes as recent as 1944-5. It mentions (p.5):
"Allied air raids on Bulgaria in the winter and spring of 1944 effectively undermined national morale,
and Russian military successes gave further evidence as to the probable outcome of the war.
By this time the weakness of the German position had become so obvious, that the attempt of
subsequent governments to sue for peace without making any essential concessions met with no
success. Only after a Russian declaration of war on Bulgaria (5 Sept. 1944), followed by
invasion, did a leftist regime under Kimon Georgiev come to power which was in a position to
sue successfully for peace."
There is a map of Bulgaria between pp. 2 & 3. On the reverse of the map is a list of sites in the nation. It lists
"Sofiya, (Sofia) (capital), 213, 162"
It IS possible that the population of Sofiya may have been greatly increased by refugees. E.g;, the population of Dresden, Germany was about 660,000 in 1939. It is believed to have swollen to more than 1 million prior to its bombing in Feb. 1945.