Overview: The convoys that sailed across the Atlantic Ocean bringing vital supplies to Britain faced one of the most deadly threats of the war. Hidden deep beneath the waves were German U-boats. This program follows the evolution of the Atlantic War, from the beginnings of the U-Boat war, to the "Happy Time" when German submarines almost brought Britain to her knees, to the eventual Allied triumph for control of the Atlantic sea-lanes. Also see the critical role that superior Allied technology played in winning the war and how British cryptographers successfully broke the German naval codes.