The official and personal correspondence of the leaders of the Bolshevik Party is one of the most interesting and little-studied sources on the history of the USSR. As a source of vital informal information, letters are unique. Soviet leaders did not keep diaries, and therefore, mainly from letters, one can glean information about those informal aspects of “big politics” (personal relationships of the Bolshevik leaders, their preferences and logic of actions, the procedure for preliminary approval of decisions, etc.) that are absent in official documents . When studying the highly centralized Soviet political system, these problems acquire special significance. Without taking them into account, it is impossible to understand the real mechanism of decision-making and the functioning of the party-state apparatus. All this is doubly true in relation to the period covered by the present volume. The documents published in it date back to the time of the Civil War and the New Economic Policy. It was a time of struggle for power both with an external enemy and within the party itself. Various factions in the Bolshevik leadership, which began to form during the civil war, openly clashed after Lenin's death. The decisive stage of this confrontation ended mainly in 1927. At this same point, which was chosen as the final point of the collection, there was an obvious departure from the new economic policy.