The military dominance of the Atlantic was a defining strategic issue of WWII. Since the invasion of France by the Nazi armies in June 1940, five French ports - Brest, Lorient, Saint-Nazaire, La Rochelle and Bordeaux - became the operational bases of the Kriegsmarine for the control of the North Atlantic. At the price of a monumental war effort, the Nazis build, in record time, gigantic fortifications that protected and rearmed returning U-Boat fleet after attacking British supply ships. Five U-Bunker networks become the nightmare of the Allies. These five superstructures remain the most important works built by the 3rd Reich outside German territory, and a crucial unknown aspect of WWII.
Now, equipped with previously unknown German national archive documents, historians Luc and Marc Braueur reveal the secrets of these super-structures for the very first time in 75 years. Meanwhile, they uncover how the Allies utilized spying and decryption to organize radically different anti-submarine counter-measures which would defeat Hitler's navy and eventually win the war.

Written and Directed by Kevin Accart ; A Galaxie Presse Production with RMC Decouverte and Cineflix Rights