Bulgaria asked by Soviet Union to increase the fleet according to a Cia report dated 29 May 1951

An item reported that in January 1951 a naval section was added to the Academy of War at Sofia, Bulgaria with the purpose of training officers for the naval staff. Such a section was brand new for Bulgaria and which seemed to be an initiative of the Soviet Union. Several Bulgarian officers believed that the Soviet Union asked the Bulgarian cabinet to increase the fleet.

Source
The report was published on www.archive.org, document number CIA-RDP82-00457R007600470023-6