cylinders were able to withstand depths up to 90 meters, triple the depth the first system that was installed on . On 21 September 1940 Gondar, under command of captain Francesco Brunetti, sailed from La Spezia to raid the naval base of Alexandria, after the first attempt by Iride had failed. In the evening of September 23, 1940 Gondar arrived in Messina, where she embarked on an SLC unit of six officers, one NCO and 3 sailors. On 25 September 1940 she secretly left for Alexandria. On 29 September Gondar was ordered to head to Tobruk, as the British naval force had sortied from Alexandria. While on her way to Tobruk, at 20:30 on the same day, Gondar spotted an enemy ship, about 1,500 meters away. The submarine tried to disengage by diving to 80 meters, however, she was almost immediately detected by ASDIC of destroyer who immediately attacked the submarine with depth charges. In two hours, at 22:30 two more ships joined the hunt, an armed trawler Sindonis, and , with additional units coming to help as the hunt went on, including Sunderland flying boats. The ongoing depth charge attacks caused serious damage to the submarine and especially to the SLC units which were beginning to flood. At 8:30 on September 30, 1940, Gondar had to surface, due to sustained damage and almost completely exhausted reserves of oxygen. Upon surfacing, the crew scuttled the boat with explosive charges. Except for electrician Luigi Longobardi, who was killed by one of the bombs dropped by a Sunderland flying boat, the entire crew was rescued and imprisoned by the British. With sinking of Gondar, the British intelligence noted the three cylinders on the deck of the submarine, and a presence of numerous divers among the crew. That raised questions about existence of special units in Regia Marina responsible for penetration into enemy ports. Notes References Adua-class submarines World War II submarines of Italy Lost submarines of Italy Maritime incidents in September 1940 World War II shipwrecks in the Mediterranean Sea 1937 ships Ships built by OTO Melara Ships built in La Spezia Submarines sunk by British warships Submarines sunk by Australian warships