ENThe article dwells on the issues of the inquiry into the stratum of dukes as faced by modern historiography when trying to answer the question where the ample stratum of tribal aristocracy that was active in the 13th century had disappeared and why it became indistinguishable in the 14th century. The following alternatives are the most feasible among the possible answers to the said questions: the sources had changed which led to the change in the concepts used. Equally important were the qualitative changes of the state as with the consolidation of the central authority and expansion of the territory the space for the activities of individual dukes became limited. This is partially accountable for the fact that representatives of the stratum of dukes were losing their significance. It was not until the late 14th century that with the increase in the scope of the source base pertaining to the internal affairs of the GDL representatives of the stratum of dukes came back in view of the researchers. [From the publication]