Recently history of the Russian Cossacks attracts domestic historians# attention more and more. Both Cossacks as a whole society, and the separate groups which because of historical tradition bear the name of Cossack armies scattered along Russian borders, mainly in southern regions are investigated in this work. The author considers that studying the Cossack society as unique historical strata, arisen during genesis and development of the Russian state and Russian people is very actual. Here it is necessary to note that Cossacks had the special form of social-political organization # an army during all period of the historical development as subethnos. This institute of the Cossack#s self-management closely cooperated with all forms of the Cossack life and was a relict of military democracy.