Geographically isolated from the strategically more important northern-tier countries of the alliance, Bulgaria participated in a few joint exercises of the Warsaw Pact along the central front opposite NATO in the German Democratic Republic (East Germany) and Czechoslovakia. Participation in that front usually was limited to small contingents. Small-scale maneuvers or command and staff exercises were held in Bulgaria in 1964 and 1972. Shield-82, the first major Warsaw Pact exercise in Bulgaria, was not conducted until 1982. That exercise involved 60,000 allied troops and included units from the northern-tier Warsaw Pact countries for the first time. The majority of participants were Soviet soldiers, however. The use of air or sea transportation instead of ground transportation across Romania, which allowed no foreign troops on its territory, constrained participation by the northern-tier Warsaw Pact countries. Part of the rationale for the Varna-Odessa ferry completed in the late 1970s was to bypass this obstacle and provide direct Soviet-Bulgarian transport of equipment and troops. The Warsaw Pact conducted a major command and staff exercise for its Southwestern Theater of Military Operations in Bulgaria in March 1984. Union-84 included general staff elements from the Soviet Union, Hungary, Romania, and Bulgaria in simulated coordination of their respective ground and naval forces.
Data as of June 1992