The article discusses issues related to the history of the Semirechensk Cossacks during the 19th and 20th centuries. The author focuses on the problem of the transformation of the identity of the Cossacks during this period. The author makes an attempt to show how, under the influence of various factors and conditions, the Cossacks passed a difficult and contradictory path: from a military, privileged class in the Tsarist period to an ethnic minority, then dissolution among the Russian ethnos in the Soviet epoch, and at the end of the 20th century their pursuit to be an ethno-cultural community. According to the author, the self-identification of the Cossacks and their external identification by the state did not always coincide in different historical periods. There were periods when self-identification and external identification of the Cossacks did not contradict each other and, on the contrary, there were moments when the state, based on its interests and goals, acted as a determining force influencing the formation of the group identity of the Cossacks, using various mechanisms and tools.