This article uses the case of the professionalization of the French armies, especially the recent modernising reform, to support the hypothesis that public institutions of State are changing and are in tension, by the process transformation, with their organizational side. On the one hand, the reform takes an institutional perspective: the missions of the institution do not change but the means are rationalised (reduction of loans, structural and territorial reorganization). On the other hand, the reform adopts a more organizational perspective: the missions are affected by the politics but the means are not appropriate (new strategic framework, trivialization of the institution). The article aims to lay the foundations of this diagnosis and show that this slide to an organizational logic calls for a restructuring of the institution on a new basis for action.