By the end of 1943 the German submarine war on Atlantic convoys was all but defeated, beaten by superior technology, code breaking and air power. With losses mounting Donitz withdrew the wolfpacks but, in a surprise change of strategy, following the D-Day landings in June 1944 he sent his U-boats into coastal waters, closer to home, where they could harass the crucial Allied supply lines to Europe. 

This offensive was, perhaps, Germany's last chance of turning the tide yet, surprisingly, this important element of the U-boat war has never been told in detail before.