Luigi Torelli was a Marconi-class submarine of the Italian navy during World War II. The vessel operated in the Atlantic from late-summer 1940 until mid-1943, then was sent to the Far East. After Italy’s surrender in 1943, the Torelli was taken over by Nazi Germany's Kriegsmarine, then, in the waning months of the war, the Japanese Imperial Navy. It was one of only two ships to serve in all three major Axis navies, the other being the Italian submarine Comandante Cappellini.
Luigi Torelli was built at the Oto shipyard in La Spezia, Italy. One of six boats of the Marconi-class submarine, which were laid down in 1938-39, Luigi Torelli was launched in January 1940. Designed as an ocean-going vessel, she was intended for operations both in the Mediterranean and in the Atlantic.
When Italy entered World War II in June 1940 the Luigi Torelli was still completing its training and shakedown period. Afterward, it conducted a short reconnaissance mission in the Gulf of Genoa, and was then dispatched to the Atlantic to Bordeaux in occupied France to serve in the Italian submarine flotilla there.
Between 11–29 September 1940, the Luigi Torelli was assigned to patrol an area just off the Azores Islands. On 5 October 1940, she reached Bordeaux. In the following weeks, the boat left port several times and made short practice missions.
On 15 January 1941, the Luigi Torelli sighted a small convoy and sank the Greek vessel Nemea, the Norwegian vessel Brask and the Greek vessel Nicolas Filinis. A fourth vessel was also damaged, but escaped due to the foul weather. This was one of the few examples of an Italian submarine achieving great results while participating in a Wolfpack attack, according to Regia Marina Italiana. Two weeks later, the Luigi Torelli sank the British vessel Urla. In July 1941, she sank the Norwegian tanker Ida Knudsen. A year later, she sank the British vessel Scottish Star and the Panamanian motor tanker Esso Copenhagen.
The Torelli had the distinction of being the first submarine to be attacked by an Allied Vickers Wellington using the Leigh light, on the night of 3 June 1942 at roughly 70 miles off the Spanish coast, suffering considerable damage but managing to reach the port of Avilés and, after an attempt to reach Bordeaux ended when an Australian Short Sunderland attacked the submarine and inflicted further damage upon it, it ended up in Santander; after emergency repairs, the submarine managed to exit the port (where the Spanish authorities intended to intern it) with a stratagem, and safely reached Bordeaux on July 15.
In 1943, the Luigi Torelli, after surviving at least two serious air attacks, was one of seven Italian submarines designated to be transformed into transports. The Italian boats, due to their dimensions, were deemed better suited for long voyages to the Far East on missions to acquire precious and rare material. The Luigi Torelli left for the Far East on 14 June 1943. The operation was under German control but the Luigi Torelli retained its Italian crew.
The Luigi Torelli was one of four Italian submarines in the Far East in 1943 when the new Italian government agreed to an armistice with the Allies. Of the four, the Luigi Torelli, Comandante Cappellini and Giuliani and their crews were temporarily interned by the Japanese. The Luigi Torelli and two other boats then passed to German U-boat command and, with mixed German and Italian crews, continued to fight against the Allies. The Kriegsmarine assigned new officers to the Luigi Torelli, renamed her the U.IT.25 and had her take part in German war operations in the Pacific.
Following the German surrender in 1945, the Luigi Torelli was again given a new name, the I-504, by the Japanese, and operated with the Imperial Japanese Navy until 30 August 1945. It retained a number of Italian submariners among its complement. The Luigi Torelli and sister submarine Comandante Cappellini were the only two ships to fly the flags of all three main Axis powers during World War II.
As the I-504, the Torelli shot down a B-25 Mitchell bomber while under Japanese flag near the very end of the war in the Pacific, allegedly the last success by an Axis naval vessel in the conflict.
Captured by the U.S. in Kobe, Japan, at the conclusion of the war, the Luigi Torelli was scuttled by the US Navy in the Kii Suido on 16 April 1946.