This study examines the role of clandestine reporting in CIA's analysis of the Warsaw Pact from 1955 to 1985. The Soviet Union established itself as a threat to the West at the end of World War II by its military occupation of eastern European countries and the attempts of its armed proxies to capture Greece and South Korea. The West countered with the formation of NATO. While the West welcomed West Germany into NATO, the Soviets established a military bloc of Communist nations with the Warsaw Treaty of May 1955. This study continues CIA's efforts to provide a detailed record of the intelligence derived from clandestine human and technical sources from that period. This intelligence was provided to US policy makers and used to assess the political and military balances and confrontations in Central Europe between the Warsaw Pact and NATO during the Cold War. As considered in this estimate, Soviet general purpose forces include: (a) theater forces, i.e., ground combat and tactical air forces plus their associated command, support, and service elements, up through the level of military districts and groups of forces; (b) naval general purpose forces, i.e., naval forces subordinate to fleets and separate flotillas, including naval air forces, but excluding ballistic missile submarine forces; and (c) military airlift and sealift elements. In addition, Soviet command and service elements providing general support to all components of the Soviet military establishment are considered where appropriate. Those Soviet forces which perform other military missions, namely strategic attack and strategic defense forces, are the subject of other National Intelligence Estimates and are discussed herein only insofar as they might be used in support of theater operations.