The rise of the Cossacks, whose origins go back to the period of Lithuanian rule in Ukraine, ushered in a new era in Ukrainian history.
Because of its importance, the Cossack era has received extensive treatment in Ukrainian historiography. Most Ukrainian historians (Kostomarov, Hrushevs'kyi, Lypyns'kyi, Doroshenko), and for that matter nineteenth-century literary figures and nurturers of the national psyche (Shevchenko, Franko), consider that the phenomenon of Cos- sackdom embodied the best characteristics of Ukrainians, which are supposedly reflected in the Cossack desire for freedom, independence, and a democratic way of life.
Others, while admitting that the Cossacks played an important historical role, criticize their tendencies toward destructive rebellion and the rejection of state formations (Kulish) or their inability to create a high standard of civilization and express an all-national purpose (Antonovych), so that Ukrainians were unable to create their own state. Whatever judgments have subsequently been passed, all Ukrainian historians agree that the Cossack phenomenon occupies a central position in the Ukrainian historical process.The Cossacks and the steppe
The Cossack phenomenon is part of the history of the steppe. During the period of Kievan Rus', large portions of southern Ukraine, in particular the steppe zone, remained only sparsely settled. This was because that region kept its age-old reputation as a stamping ground for nomadic peoples, the most recent of whom during Kievan times were the Pechenegs and Polovtsians. Following the Mongol invasion of the mid-thirteenth century, the line where towns, villages, and farming communities ended receded even farther north. The result was a marked decrease in the number of inhabitants in the former principalities of Kiev and Pereiaslav, which by the fourteenth century had been annexed by Lithuania but were still subject to destructive raids from Mongolo-Tatar-held territory farther south. Although the Kiev and Pereiaslav regions were never entirely depopulated, by the fifteenth century they had an average of a mere 8 inhabitants per square mile (3 inhabitants per square kilometer), whereas in western Ukrainian lands such as parts of Galicia, Volhynia, and Podolia the average density at times