The article investigates the role of historical writing of participants in “Free Cossackdom” movement in the process of construction of the Cossack nation in the context of post 1917 emigration. Amateur historians under scrutiny viewed their intellectual pursuits in the emigration as a means to assert a distinct Cossack national identity and contribute to a national revival of the Cossacks. The author suggests that the outcome of the break up of the empire and the Civil War forced leaders of the Cossack diaspora reassess the history of the Cossackdom and its relationship to the Russian state and Russian nation. The ideologues of the “Free Cossackdom” movement criticized the Russian mainstream historiography (“the state school”) for ignoring the history of Cossacks, maintained that Cossacks constituted a separate Slavic nationality apart from the Great Russians, Belorussians, and Ukrainians, and even possessed a unique statehood republican tradition in early modern time. Stressing cultural and political differences between the Russians and the Cossacks, the Cossack émigré leaders stopped short of calling on to develop a separate national language. Cossack historians suggested a different perspective on the nature of the Civil war in Russia. According to this perspective, it was the war between the reestablished Cossack states and a new Russian colonialism in the disguise of Bolshevism. The author concludes that although Cossack historical writing in the emigration was informed by politics and the goals of nation-building, it could provide valuable insights about the history of Cossacks and contribute to a diverse picture of Russian historiographic tradition.