Between 1944 and 1945, German troops built important military facilities in the area of ​​Alto Garda, exploiting military works dating back to the Great War and the imposing Adige-Garda river tunnel.

An emblematic example of this infrastructure and its operational results is given by the design and construction, carried out by Caproni industries, of the Campini-De Bernardi submarine prototype. The assault vehicle ensured attack effectiveness superior to that of traditional aircraft or naval means, thanks to technical characteristics largely derived from aeronautical experience. An innovative propulsion system, based on oxygen, guaranteed the ability to approach enemy vessels silently and without producing bubbles on the surface, and to attack them by launching two torpedoes.

The maximum speed that could be reached is surprising. The designer clearly aimed for a speed of around 30 knots (about 54 km/h) when the boat was completely submerged. An enormity for that time. The absolutely brilliant part of the entire project was the operation of the propeller during the immersion phase, powered by large oxygen cylinders. The experimentation took place at Forte San Nicolò in Riva del Garda, a place equipped with a port and protected from air attacks.

The program also interested the Japanese Navy, which tried to acquire the designs. Shortly before the arrival of the Allies, the SS destroyed much of the archives and sank one of the prototypes. The other is said to have been transported to the United States by American intelligence services.