Throughout Vietnam's medieval history, the military aristocracy has always played a crucial role in government, relying on private armies that formed the basis of the armed forces. Nevertheless, in the second half of the 17th –– first quarter of the 18th centuries in the northern part of Vietnam, with the temporary cessation of wars, there has been a transition from military dictatorship and related forms of government to a state in which, at least formally, the first place would be given to civilian officials. This transition required a major reorganization of the army, which was carried out in two stages. At the first stage, in 1674, under the ruler Trinh Tac, the administration of the northern part of the country finally ceased campaigns against the separatists in the south and significantly limited the military's ability to interfere in the affairs of the civilian government. At the same time, private military armies and the principle of recruiting professional military personnel, mainly from the South, were preserved. At the second stage, in the 1720s, under Trinh Cuong, it was decided to abandon professional detachments as the basis of the armed forces completely, and troops began to be formed through recruitment and centralized training of senior and middle-level commanders at the military schools. The latter of these reforms caused significant damage to the combat capability of the troops, which clearly manifested during the civil wars that broke out in the country in the 1730s–40s.