The article reveals the work of the Soviet authorities (NKGB-KGB) on the unification of the All-Ukrainian Union of Christians of the Pentecostal Evangelical Faith (UCPEF/KhEV) with the All-Union Council of Evangelical Baptist Christians (ACEBC/VSEKhB).The article also is devoted to the study of the role of the bodies of Soviet state security in carrying out of religious policy in Protestant environment in the territory of Soviet Ukraine on the example of their creation of a «legendary» religious center – All-Union Council of Evangelical Baptist Christians, as well as the apparatus of its republican and regional representatives (i.e. senior elders/presbyters). The article also highlights the plans of the Soviet state security agencies for the use of the leadership of ACEBC in the implementation of agent-operational measures to absorb other related to ACEBC protestant movements of the USSR (Pentecostals, Darbists, reformists etc.), to reduce their numbers, to subordinate influence to the organs of Soviet authorities and, ultimately, to lead to moral and physical decay. For the first time, the article publishes the name of undercover operations («FANATICS» and «PROPHETS»), which were carried out by the NKGB-KGB bodies in the protestant milieu of the Ukrainian SSR in 1943-1957, and also indicates, for the first time, the operational pseudonyms of secret agents of the NKGB-KGB, who were involved in these operations. For example M. Melnikov – agent “MIRGORODSKIY”, G. Ponurko – agent “GOROSHKO”, M. Boot – agent “LYSOV” and others, who operated in a Protestant religious environment with the decryption of their operational pseudonymsand also indicates the intelligence and operational activities that were carried out by the Soviet security organs in the Protestant environment, which were aimed at subordinating this environment to the influence of the Soviet special services.