The historiography on civil–military relations in the early years of the Weimar Republic has concentrated on issues such as the soldiers' councils, the threat of a radical left-wing uprising and the difficulties of demobilization. This article broadens the perspective on co-operation between the officer corps and the government, arguing that the collapse of the Kaiserreich provided an opportunity to remake the state. For very different reasons, liberal and socialist politicians and officers shared a community of interests in centralizing the Reich. Officers believed that a more centralized state was more effective in military and foreign policy terms. Whereas other incidents of co-operation were due to urgent necessity, the establishment of the Reichswehr Ministry showed that the new state could potentially serve the longer term agenda of the officer corps. However the plans for a centralized Reichswehr Ministry were opposed by those who held power in the federal states, particularly in southern Germany. With support from the National Assembly and the cabinet, opposition from the states was overcome. This episode in Weimar history shows that the view of antagonistic civil–military relations must be modified to take account of the ways in which the officer corps sought to exploit the possibilities opened up by the German revolution of 1918.