| Conflict: | Raid on Algiers |
| Partof: | the Battle of the Mediterranean of Second World War |
| Date: | 11 December 1942 |
| Place: | Algiers, Mediterranean Sea |
| Result: | Italian victory |
| Combatant1: |  United Kingdom United States Norway |
| Commander1: | Morgan Morgan-Giles |
| Commander2: | Mario Arillo |
| Strength1: | Harbour defences |
| Strength2: | 1 submarine 3 Human torpedoes 10 frogmen |
| Casualties1: | 1 cargo ship sunk 1 tanker damaged 2 cargo ships damaged 1 military transport ship damaged[1] |
| Casualties2: | 16 captured |
The Raid on Algiers took place on 11 December 1942, in the Algiers harbour. Italian manned torpedoes and commando frogmen from the Decima Flottiglia MAS were brought to Algiers aboard the . The participating commandos were captured after setting limpet mines which sank two Allied ships and damaged two more.
On 4 December 1942,, a submarine of the Italian Royal Navy (Regia Marina), left the naval base of La Spezia, carrying three manned torpedoes and 10 commando frogmen. Air reconnaissance had discovered 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.[2] On the evening of 10 December, Ambra reached Algiers at a depth of 18m (59feet). One of the swimmers was employed as scout on the surface, and he guided the submarine toward a position 2000m (7,000feet) from the southern entrance to the harbour. He spotted six steamers at 21:45, and informed the presence of targets to Ambra by phone. The other swimmers and the manned torpedoes begun to emerge at 23:45 after some delay. The observer reported an intense reaction from the harbour defences.[3] The submarine awaited to recover the operators until 03:00, an hour after the original time set. Then the scout swimmer was recalled on board and Ambra departed back to La Spezia.[4] Meanwhile, at 05:00, the explosions started to rock the freighters. The Norwegian[5] Berta (1,493 tons) was sunk, while Ocean Vanquisher (7,174 tons),[6] Empire Centaur (7,041 tons) and Armatan (4,587 tons) were heavily damaged. The American landing ship LSM-59 became stranded on the beach. Sixteen Italian divers were captured.[7]