Based on new archival sources, the monograph describes the armed forces of Ukraine in the first half of the 18th century, examines the acquisition, mobilization, organization, armament and support of the Ukrainian Cossack army, guard and auxiliary service in Ukraine. The state of the Zaporizhzhya army during this period is separately covered. The author shows the dependence of the structure, material and technical equipment of the Ukrainian armed forces on the level of development of the Cossack economy, differentiation of the Cossacks, the development of serfdom, class and social struggle and the policy of the tsarist government in Ukraine.