This article presents a review of the diary entries of Kaluga physician Mikhail Vasilyevich Ustryalov (1892–1944), the younger brother of the renowned philosopher and one of the ideologists of the «Smena Vekh» movement Nikolai Vasilyevich Ustryalov (1890–1937). The entries cover the periods of the First Russian Revolution of 1905–1907, the First World War and the revolutionary events of 1917–1918, and the Great Patriotic War (from November 1941 to August 1943). The entries, made in Kaluga, Moscow, and on the Southwestern Front, reflect the author’s perception of major political events, everyday life in a provincial town, and the situation at the front in 1917. Of particular interest are the entries made in Kaluga during the Nazi occupation in 1941 and in the first months after the city’s liberation.

The article deals, based on the archival documents and published materials, with the contribution of the well-known folklorist and literary critic Yuri Matveyevich Sokolov (1889–1941) to the development and formation of the Library of the State Historical Museum in the post-revolutionary period, and his activities as head of the museum library in 1922–1929, as well, as the circumstances of his forced departure from the Historical Museum due to the conflict with the Museum's management. A number of published documents are being introduced into scientific circulation for the first time.

Based on a wide range of archival documents, the biographies of Siberian “fiery revolutionaries” – Alexander Vasilievich Tsytovich (1873–1942) and his wife – Anna Pavlovna, nee Tarelkina (1879 – after 1957), active participants in the Irkutsk Social Democratic underground of 1904–1912, then – of political emigrants. Information is presented on the activities of A.V.Tsytovich after returning to Soviet Russia in 1919, on his work as director of the Library of the State Historical Museum (1929–1933).