The 'Raid on Algiers' was made by Italian manned torpedoes and frogmen on Allied shipping in the harbour of Algiers (11 December 1942).
Italian manned torpedoes and commando frogmen of the 10a Flottiglia MAS were delivered to the waters just off Algiers by the 'Perla' class submarine Ambra, which was commanded by Mario Arillo. All of the Italians who entered the harbour were taken prisoner, although only after they had set limpet mines which sank two Allied ships and damaged two more.
On 4 December 1942, Ambra departed the Italian naval base of La Spezia carrying three manned torpedoes and 10 commando frogmen. Air reconnaissance had established that the port of Algiers was crowded with Allied cargo ships, so the Italian high command decided to launch an operation involving both human torpedoes and combat swimmers carrying limpet mines.
During the evening of 10 December, Ambra reached the area of Algiers, and at a depth of 59 ft (18 m) deployed one of the frogmen to scout on the surface and guided the submarine toward a position 2,185 yards (2000 m) from the southern entrance to the harbour. The scout spotted six vessels at 21.45, and used a phone connection to inform Ambra of the possible targets' locations. The other swimmers and the manned torpedoes begun to emerge at 23.45 after some delay. The scout reported an intense reaction from the harbour defences, and the submarine waited until 03.00, one hour later than planned, to recover the men. The scout was then recalled on board and Ambra departed back to La Spezia.
Meanwhile, at 05.00, explosions started to rock the freighters. The 1,493-ton Norwegian Berta was sunk, while the British 7,174-ton Ocean Vanquisher, 7,041-ton Empire Centaur and 4,587-ton Armatan were severely damaged. The US landing ship LSM-59 became stranded on the beach.
All 16 of the Italian attackers survived and were taken prisoner.