sentences:  In the period between the two World Wars the Reichsmarine of the Weimar Republic was not allowed to build submarines according to the Treaty of Versailles; development was undertaken secretly through a Dutch company NV Ingenieurskantoor voor Scheepsbouw before the mid-1930s.The terms of the Anglo-German naval agreement acknowledged the official building of new U-boats.This list contains the German U-boats types prior or during the First World War.