However, there was a break of several years in his post–graduate studies because of his commission in the Soviet military's technical forces during the second world war.

[4] In June 1939, he completed his graduation in history at the Leningrad State University, with a recommendation for post–graduation at the Institute of Ethnography of the Academy of Sciences of the USSR.

[4] He completed the Doktor Nauk in Historical Sciences[3] at the academy in 1952, with the thesis titled "Происхождение Мусульманского Населения Северной Индии" (The Origin of the Muslim Population of Northern India).

The Soviet military units had benefited in some of their onerous combat tasks from his knowledge as a topographer.

[9] During his service years in the Soviet Military, he visited Romania, Poland, Germany, and Czechoslovakia.

[7] Kudryavtsev was a "senior scientific worker" at the Institute of Ethnography of the Academy of Sciences of the Soviet Union.

[14] He concurred with M. N. Srinivas's categorization of relationships in the Indian society in two categories — vertical (inter-caste) and horizontal (intra-caste).

According to Kudryavtsev, "the core of the caste system, in the form of the varnas, took shape over 2,000 years ago — almost in the Vedic period.

The caste system became increasingly sophisticated with the development of technology, the growing division of labor, and the emergence of new occupations.