The publication presents previously unknown letters to Sergey Ozhegov of the late 1940s – early 1960s, which reveal facts of his scientific biography. The aim of this work is to introduce into scientific discourse rare archival documents on the history of Russian linguistics, and also to study linguistic polemics in the USSR in the era of the onslaught of the Marrism of the end of the 1940s. The main methods of studying the material are historical-linguistic, lexicographic, sociolinguistic and linguistic source analysis (search, decoding and commenting on archival texts). In the course of the research of documentary materials, the author has revealed new facts testifying to the change of a vector of scientific views on explanatory lexicography as a whole which, unlike the previous dictionary projects, was not adapted to academic needs, and first of all solved practical problems of explaining the actual lexicon of the 20th century. The article notes that one of the key issues of the dictionary work of that time was the interpretation of Sovietisms, on the one hand, and religious words and expressions, on the other. The archaic vocabulary (“merchant” and church elements) became the object of fierce criticism of Ozhegov’s opponents. Scholars and non-philological readers, polemicizing with Ozhegov, paid special attention to reviews and analysis of semantic, stylistic and cultural-historical realities of dictionary entries. Ozhegov’s respondents also discussed the difficult fate of the dictionary. The published letters contain semi-official reviews from both famous scholars (A.P. Evgenieva, Ya.M. Endzelin, R.R. Gel’gardt, J.V. Loja) and ordinary readers of The Dictionary, they reveal Ozhegov as a person of special gift loving his native language. These letters provide valuable material for the analysis of linguistic homeland studies of the period of struggle between the two ideologies in science. The letters reveal new facts of Ozhegov’s editorial work, discuss the criticism of the publication in the press, note its strengths and weaknesses. The article emphasizes the sociocultural aspect of Ozhegov’s interpretations and the ambiguity of their perception by contemporaries. The Dictionary is included in the context of general linguistic ideas by D.N. Ushakov and L.V. Shcherba. The high pedagogical value of this source is indicated. The published archival materials confirm a unique fact in the scientific practice of the mid-20th century: the emergence of a popular explanatory dictionary reflecting the cultural constants of the time and serving as a reliable tool for self-education. The article is of interest to historiographers of science, lexicologists and lexicographers, linguaculturologists, sociolinguists.