The 'Raid on Algiers' was an Italian attack on Allied shipping in the harbour of Algiers by manned torpedoes and commando frogmen of the 10a Flottiglia MAS delivered to Algiers by the submarine Ambra (11 December 1941).

On 4 December, Ambra departed the naval base at La Spezia, carrying three manned torpedoes and 10 commando frogmen after aerial reconnaissance had revealed that the port of Algiers was crowded with Allied cargo ships. The Italian naval high command decided to launch a combined operation involving both human torpedoes and combat swimmers carrying limpet mines.

On the evening of 10 December, Ambra approached Algiers at a depth of 59 ft (18 m). One of the swimmers was employed as scout on the surface, and guided the submarine toward a position 2,185 yards (2000 m) from the harbour’s southern entrance. He spotted six ships at 21.45, and used a telephone to inform the submarine’s captain of presence of targets. The other swimmers and the manned torpedoes began to emerge at 23.45 after some delay.

The observer reported an intense reaction from the harbour defences, and the submarine waited until 03.00 to recover the Italian frogmen. This was one hour after the original time set. The scout swimmer was then recalled into the submarine, which headed back toward La Spezia.

Meanwhile, at 05.00 explosions started to rock the freighters. The 1,493-tin Norwegian Berta was sunk, while the 7,174-ton British Ocean Vanquisher, 7,041-ton British Empire Centaur and 4,587-ton British Armatan were severely damaged. The US landing ship LSM-59 became stranded on the beach.

All of the Italian frogmen were taken prisoner.