The period of the Weimar Republic constitutes an interesting example of the state's approach to the issue of building of the country's security, while being at the same time subject to international military restrictions. In this field East Prussia played a very important role. Reasons of ideological and historical nature as well as the location of the province, turned it into the object of interest of both German and Polish staff officers. Separated from the rest of the state by the sea and the so-called 'Polish corridor', East Prussia had to rely mainly on its own defensive potential. That is the reason of the permanent care for modernization and development of the existing system of stable and field fortifications. This concern with defensive potential of the 'East Prussia bastion', was not determined only by the defensive strategy. In the planning layer, the conspicuous role that East Prussia played in the engagement of Polish armed forces was noticed. Yet, above all, offensive values pertaining to the possibility of capturing of Pomerania or conducting attacks in the rear of the main Polish forces, concentrated in the belt of Great Poland and Pomerania, were appreciated.