Two officers of the Regia Marina's "Genio Navale" (engineering) generated the most popular submarine designs in use by the Italian Navy's submarine fleet: Cavallini and Bernardis. The "Bernardis" were produced in several classes and they all evolved from the "Vector Pisani Class", built starting in 1925. Three years later came the "Bandiera Class" and two years later, in 1930, the almost identical “Squalo Class”. Later evolutions, namely the “Glauco Class” in 1932, the “Marcello Class” in 1937”, and the “Marconi Class” in 1939, made the Bernardis true oceanic submarines and they are covered in a different section of this site.

Colonel Curio Bernardis, later General, began the design of a new class of submarines merging the previous design by Laurenti with new, and quite innovative ideas. The goal was to create boats capable of reaching greater depths relying more on the structural integrity of the external part of the resistant hull, rather than the thickness of the internal beans. Bernardis’ design called for a traditional circular hull enclosed at both ends by a semispherical cup. Whiel the ballast tanks were positioned at the end of the resistant hull, inside this there was an additional tank which allowed for high dept operations since it could be emptied both utilizing compressed air and pumps.

The original Bernardis were not very successful, but their evolution gave birth to the Marcello and Marconi classes, some of the most successful products of the Italian submarine shipbuilding effort. The Vector Pisani Class included four boats built between 1925 and 1929, and as soon as they underwent testing at sea a serious flaw was immediately discovered: the boat tended to roll quite heavily. To overcome this serious deficiency, the shipyard added some small saddle tanks which, while partially solving the problem, caused the surface speed to drop from 17 to 15 knots, and the submerged one from 10 to 8. To improve stability, some of the equipment was rearranged within the delicate balance allowed by submarine construction.

Eventually, these saddle tanks were integrated in the project and become part of the Bernardis design. Unfortunately, while the problem was still undergoing studying on the Pisani, the Bandiera were already in advanced state of completion, thus they also had to be retrofitted. Furthermore, on the Bandiera another problem had to be corrected, the boat tendency to dip down by the bow. This problem was resolved by installing a special auto-filling tank which, while the unit was on the surface, would stay empty and give extra buoyancy, while in immersion would fill itself up. Further modifications to the Bardiera gave this class the unique bow which earned the four boats the nickname of “big nose”, or “nasone”. Unfortunately, even the third evolution of this series of submarines, the “Squalo Class”, was laid down too soon and they had to be heavily modified. Eventually, the first 12 boat of the Bernardis type laid the foundations for future design, first the 2 “Glauco” and then the 11 Marcello and 6 Marconi.