The 'Raid on Alexandria' was an Italian attack by frogmen of the 10a Flottiglia MAS on British warships in the harbour of Alexandria on the north coast of Egypt (19 December 1941).

On 3 December, the Italian submarine Scirè, under the command of Tenente di Vascello Junio Valerio Borghese, departed the naval base of La Spezia carrying three manned torpedoes, generally known as maiali (pigs) by the Italians. At the island of Léros, which was the Italian navy’s main base in the Aegean Sea, the submarine secretly took on board the six men to crew the manned torpedoes.

On 19 December Scirè, at a depth of some 50 ft (15 m), released the manned torpedoes at a distance of some 1.3 miles (2.1 km) from Alexandria’s commercial harbour, and these entered the naval base when the British opened their defences to let three of their destroyers pass. There were many difficulties for Luigi Durand de la Penne and Emilio Bianchi on maiale no. 221. Firstly, the engine of their torpedo stopped and the two frogmen had to push it manually; and secondly, Bianchi had to surface as a result of problems with his oxygen provider, so that de la Penne had to push the maiale on his own to the position where the battleship Valiant lay. There he successfully placed the limpet mine just under the hull of the battleship. Both men had then to surface, and as Bianchi was hurt they were discovered and taken prisoner.

Under interrogation, both men kept silent and were confined in a compartment aboard Valiant, below the water line, and coincidentally just over the place where their mine had been placed. Some 15 minutes before the explosion, de la Penne asked to meet with Valiant's Captain C. E. Morgan, informed the British officer of the imminent explosion but refused to give further information. The Italian was then returned to the compartment. When the mine exploded just beneath them, neither of the Italians was severely injured, de la Penne receiving only a minor injury to the head.

Meanwhile, Antonio Marceglia and Spartaco Schergat on maiale no. 223 had attached their device 5 ft (1.5 m) below the battleship Queen Elizabeth's keel as planned. They successfully left the harbour area at 04.30, and slipped through Alexandria posing as French sailors. They were captured two days later at Rosetta by the Egyptian police while awaiting rescue by Scirè and handed over to the British.

Vincenzo Martellotta and Mario Marino on maiale nº 222 searched in vain for an aircraft carrier purportedly moored at Alexandria, but after some time decided to attack the 7,554-ton Norwegian tanker Sagona. Marino fixed the mine under the tanker’s stern at 02.55. Both divers managed to land unmolested, but were eventually arrested at an Egyptian police checkpoint.

In the end, all the frogmen was taken prisoner, but had succeeded in severely damaging both Queen Elizabeth and Valiant, disabling them for nine and six months respectively. Eight members of Queen Elizabeth's crew were killed. Sagona lost her stern section and the destroyer Jervis, one of four alongside to refuel, was badly damaged.

This Italian success marked a major, albeit temporary, change of fortune against the Allies from the strategic point of view during the next six months. The Italian fleet had temporarily wrested naval supremacy in the east-central Mediterranean from the Royal Navy.

Valiant was towed to Admiralty Floating Dock No. 5 on 21 December for temporary repairs and was under repair at Alexandria until April 1942, when she sailed to Durban in South Africa for more permanent repair. By August, she was operating with Force 'B' off Africa in exercises for the defence of East Africa and for the 'Ironclad' battle for Madagascar.

Queen Elizabeth drydocked in Alexandria for temporary repairs until late in June, when she sailed for the USA for repairs and refit in a programme which ended the following June, when the ship sailed to the UK for the completion of her refit.

Jervis was repaired and operational again by the end of January, and Sagona was towed back to the UK, where her repair was not completed until 1946.