ENThe issues of organization of state defenсe in according to the Statutes of the Grand Duchy of Lithuania 1529, 1566, 1588 are considered. The prerequisites for the formation of military legislation, based on the norms of customary law and the decrees of the supreme authority, are characterized. It is noted that in the XVI century principles of organization and activities of the army were systematized by the Statutes of the Grand Duchy of Lithuania. The important role of the pospolite ruszenie in the structure of the armed forces of the state is shown. Based on the analysis of the texts of the Statutes of the Grand Duchy of Lithuania, the norms of compulsory military service and categories of the people liable for service, features of the mobilization of the troops and powers of the officers are revealed. The questions of military discipline, as well as the order of formation and maintenance of the mercenary army are being investigated.