This publication presents extensive factual material, including information on the history of the creation and development of the Workers' and Peasants' Navy. A special place in the book is given to the coverage of the pre-war period in its life. The author has attempted, on the basis of available archival material and the memoirs of direct participants in military operations in various naval theaters of the country, to analyze the state and level of training of Soviet fleets and flotillas, their combat readiness to repel possible aggression.