It was a strange mix of fugitive peasants of various nationalities, but in first turn they were russians, nevertheless. Fugitive peasants and robbers, they were a real problem not only for Poles and Turks, but for Russians as well.
Is that true?
There seems to be different versions...
...Cossacks are a group of several peoples living in the southern steppe regions of Eastern Europe and Asiatic Russia, famous for their self-reliance and military skill, particularly horsemanship. Cossack may also refer to a member of a Cossack military unit. They are a non-exclusive ethnic group...
Could it be that because they weren't so taken with the upcoming Stalinism/Bolshevism that they got a bad name by the new rulers?
...Following the defeat of the White Army, a policy of Decossackization (Raskazachivaniye) took place on the surviving Cossacks and their homelands since they were viewed as potential threat to the new regime. This mostly involved dividing their territory amongst other divisions and giving it to new autonomous republics of minorities, and then actively encouraging settlement of these territories with those peoples. This was especially true for the Terek Cossacks land.
The Cossack homelands were often very fertile, and during the collectivization campaign many Cossacks shared the fate of kulaks. The famine of 1933 hit the Don and Kuban territory the hardest. According to Michael Kort, "During 1919 and 1920, out of a population of approximately 3 million, the Bolshevik regime killed or deported an estimated 300,000 to 500,000 Cossacks" [2]....