"The Allied Campaign in North-west Europe, 6 June 1944 - 7 May 1945" Crossing the Seine and the advance to the Siegfried Line 24 August - December 1944: A forty-foot circle hole in the roof of a U-boat pen in Brest which had received a direct hit during the Allied bombardment. The capture of the deep water ports of Brittany did not greatly help the Allies, however, since the Germans had, as in Cherbourg, carried out thorough demolition of the port facilities before surrendering.