The Devil's Rock - Region 0 DVD

Two Kiwi commandos are assigned to the Channel Islands to blow up a giant gun at a beach head fortress. But once inside the foreboding structure they hear unearthly screams and investigate the dark tunnel system to discover the cause. There they find the head of Hitler's occult Gestapo squadron who has been experimenting with incantations from an ancient tome to allow a succubus to cross over from Hell. It's all part of a master plan to win the war on the eve of D-Day.