Introduction. The study of Peter the Great’s Russian naval personnel is a long-living tradition. The presence of Rear Admiral Denis S. Kalmykov — an ethnic Kalmyk — among the Emperor’s officers has so far been perceived only as an anecdote, and in the 1930s–1970s served a starting point for the creation of a novel, play and films. Goals. The paper seeks to specify and actualize biographical data of D. Kalmykov and J. Brant, and examine the latter’s paths in corresponding historical contexts. Materials and methods. The work deals with documents that make it possible to significantly clarify the biography of D. Kalmykov, prove his Kalmyk origin. So, in youth he had been a slave of N. G. Spafaria-Milescu and attended the Navigation School with the latter’s son M. N. Spafariev. However, during his studies abroad D. Kalmykov was no longer a lackey, and the most dramatic element of the anecdote about a servant who had been taking classes instead of his master — namely, an exam administered by Peter I which promoted the servant to an officer’s rank and defined his master as sailor — is fiction. Results. The article sheds light on details of D. Kalmykov’s biography, in particular, the analysis of his handwriting patterns presumes he may have been apprentice to a highly qualified book copyist, and refutes a number of falsehoods, such as that it was D. Kalmykov who introduced the ‘Kalmyk’ knot into Russian naval practices. It also supports Kalmyk origin of another officer — colonel-rank Captain Jacob Brant, and specifies some details of his life. Conclusions. The fact D. Kalmykov had been an ethnic Kalmyk serf to the remarkable statesman N. G. Spafaria-Milescu may be considered well proved. The former had also obtained excellent writing skills from a qualified book copyist in youth. And his ‘servant-to-admiral’ career was unique enough to the eighteenth-and nineteenth-century Russian Navy. Furthermore, J. Brant might also have been an ethnic Kalmyk servant of the Dutch merchant K. Brant, and in view of his non-noble backgrounds his colonel-rank captainship can definitely be viewed as a most significant achievement.