Adolf Hitler had decided by early November 1939 on forcing an end to the war by invading France. In order to avoid the heavily-defended Maginot Line the Germans had to invade Belgium, the Netherlands and Luxembourg in order to invade France. With the prospect of the Channel ports falling under Kriegsmarine (the German Navy) control, and attempting to anticipate the obvious next step that might entail, Grand Admiral (Großadmiral) Erich Raeder (head of the Kriegsmarine) instructed his operations officer, Kapitän Hans Jürgen Reinicke, to draw up a document examining "the possibility of troop landings in England should the future progress of the war make the problem arise." Reinicke spent five days on this study and set forth the following prerequisites