The Central State Archive of the City of Moscow (TsGA of Moscow) holds documents that expand existing notions on the Soviet military construction of 1918-19, the formation of military intelligence and counterintelligence in Soviet Russia, and the “third wave” of mass Red terror in 1919. These documents are mostly found in the seemingly insignificant fond of the Serpukhov uezd committee of the Russian Communist Party (Bolsheviks). Since in the autumn 1918 – summer 1919, the Field Staff of the Revolutionary Military Council of the Republic was located in Serpukhov and its military commissar, head of the registration department, and founder of the Soviet military intelligence, S. I. Aralov actively worked in the Serpukhov uezd committee, the committee protocols are of great importance for studying the formation of the Red Army and its special services. The documents on admission to the Russian Communist Party (Bolsheviks) and party registration of the Field Staff senior officials, brothers Alexei and Pavel Vasiliev contain new information on the personnel continuity in the Operational Department of the People's Commissariat for Military Affairs of the RSFSR and the Field Staff. Protocols of the reports of the old Bolshevik A.A. Antonov at sessions of the Serpukhov uezd bodies of the Russian Communist Party (Bolsheviks) clarify the existing notions on the calamity of June 1919, which took place on the eve of the events associated with the arrest of the first Commander-in-Chief of all the armed forces of the Republic J. J. V?cietis and some of his employees in July 1919, the cleaning of the Field Staff initiated by the old Bolshevik, longtime associate of Lenin S.I. Gusev who replaced S.I. Aralov at his posts. There are also documents containing information on the Bolshevik leadership reaction to the events related to the explosion in the building of the Moscow Committee of the Russian Communist Party (Bolsheviks) on September 25, 1919, when 12 Bolsheviks were killed and 55 received wounds of varying severity. These materials complement and correct data from the documents stored in the federal archives, in particular, in the Russian State Military Archive, which keeps documents on the history of the Red Army in 1918-41. For instance, it turns out that it was decided to arrest the bourgeoisie and other “counter-revolutionaries” with their subsequent imprisonment in a concentration camp created specifically for this purpose in Serpukhov district.