INFORMATION:
The large deep water port of Brest was large enough to receive battle ships like the Tirpitz. Also a U-boat pen was constructed inside the harbour. That meant that the whole area around the entrance to the Rade de Brest had to be defended.

After the attack on the lock gate at St Nazaire the defence was again increased. A batterie of four 28.0cm SKL/40 guns were placed in three open emplacements and one in a large casemate. These guns were targeted from a very large fire control post (PDT).