The 'Battle of Cape Passero' was a naval action fought between the British light cruiser Ajax and a force of seven Italian destroyers and torpedo boats off Cape Passero, to the south-east of Sicily, within the context of the British 'MB6' operation to deliver supplies to Malta (12 October 1940).

In October 1940, Admiral Sir Andrew Cunningham’s Mediterranean Fleet mounted the 'MB6' resupply operation to Malta from Alexandria. The convoy comprised four cargo ships escorted by two anti-aircraft light cruisers and four destroyers. The screening force was led by Cunningham’s flagship, the battleship Warspite, and included three other battleships, two aircraft carriers, six cruisers and 16 destroyers. The only remarkable incident during the convoy was some damage to the destroyer Imperial when she ran into a minefield. The merchantmen reached their destination on 11 October. Until that time, adverse weather had prevented any Italian intervention, but an aeroplane spotted the British ships, as they returned toward Alexandria shortly after departing Malta. Meanwhile, the light cruiser Ajax had been detached from the other cruisers for a scouting mission.

The Italian commander-in-chief, Ammiraglio di Squadra Inigo Campioni, ordered a force of destroyers to the area of Cape Bon, in the north-east of Tunisia, in case the British warships were making passage to Gibraltar. In Campioni’s view, it was too late for the Italian battleships and cruisers to operate against the convoy. A flotilla of four destroyers and three torpedo boats was, at the same time, patrolling between 35° N and 35° N, about 3.5 miles (5.6 km) apart, in full moonlight. The Italian destroyers were Artigliere, Camicia Nera, Aviere and Geniere, and the torpedo boats Ariel, Alcione and Airone.

At 01.37, Ajax was sighted by Alcione steaming to the east 19,575 yards (17900 m) distant on the port side. At 01.48, the three torpedo boats were at full speed closing the British cruiser, which was completely unaware of the approaching Italian ships. At 01.57, Alcione launched two torpedoes at a range of 1,860 yards (1700 m), and Capitano di Fregata Banfi, commander of the Italian formation, ordered his flagship Airone to open fire with her 100-mm (3.94-in) main guns, followed by her sister ships. Three of the Italian rounds hit home, two on the light cruiser’s bridge and the third 6 ft (1.8 m) below the waterline.

Realising that she was being attacked, Ajax and opened fire on the nearest torpedo boat, Ariel, while at full speed. Ariel was shattered by the 6-in (152.4-mm) salvoes and sank 20 minutes later, although she may have been able to fire a torpedo. Capitano di Fregata Mario Ruta, his second in command, and most of the crew were killed. Airone was the next Italian ship to be hit, but managed to launch two torpedoes before being disabled, catching fire almost immediately, her bridge and upper deck machine gunned by Ajax at short range. Airone sank a few hours later, Banfi being among the survivors. Alcione, the only undamaged Italian warship, then broke contact at 02.03.

Meanwhile, after manoeuvring during the fighting, Ajax resumed her course to the east. At 02.15, her fire-control radar detected two Italian destroyers, whose commander, Capitano di Vascello Carlo Margottini, had sighted the firing from the south. A radio malfunction had prevented Margottini from attacking in full strength, when three of his destroyers had headed to the north-west instead of north as ordered. Aviere was battered by a sudden broadside from the British cruiser, preventing a torpedo attack and forcing her to withdraw to the south with heavy damage. Artigliere managed to fire a torpedo and four full 120-mm (4.72-in) gun salvoes at a range of 2,845 yards (2600 m) before being hit and crippled. The torpedo missed, but four rounds struck two of Ajax's 4-in (101.6-mm) secondary gun turrets, destroyed her port whaler and disabled her radar. After unsuccessfully firing at Camicia Nera, Ajax broke off the action. She had fired 490 rounds of different calibres and four torpedoes; 13 of her ship’s company had been killed and 22 wounded, while the cruiser required a month of repairs before she returned to active service.

The disabled Artigliere, with her captain and most staff officers killed, was taken in tow by Camicia Nera. The two ships were surprised at first light by the heavy cruiser York, which drove off Camicia Nera before sinking the drifting Artigliere with a torpedo. The survivors were rescued on the next day by Italian ships.

The 'Battle of Cape Bon' had been the Regia Marina’s first experience of the Royal Navy’s superior skills and equipment in night actions. The extensive use of starshells, searchlights and incendiary rounds by the Royal Navy had to be countered before the Italians could close the technical gap. The Italians also suspected the British use of radar, but at this time this was only a speculation. The Italians came to the conclusion that poor Italian air surveillance had prevented a quick reaction by the Italian heavy units, handing the tactical advantage to the British of avoiding contact in unfavourable tactical situations.