The Mediterranean setting did not eliminate Italy's need for large boats. Reaching the Atlantic demanded a submerged passage through Gibraltar against a current of roughly seven knots, making official underwater speeds near eight knots operationally valuable. Published endurance figures of about 110 nautical miles at three knots also reveal how tightly battery capacity constrained the passage. The boats' endurance and speed nevertheless allowed Italian submarines to serve from Atlantic bases and, unlike many German U-boats entering the Mediterranean, retain a practical route home.
Chapter · 6:08-9:52
Large Italian submarines and the Gibraltar current
Italy's unusually large ocean-going submarines combined endurance with enough underwater speed to fight the current through the Strait of Gibraltar.