The 'Battle of Cape Matapan was a naval battle fought between British and Italian force off Cape Matapan on the south-western coast of Greece’s Peloponnesian peninsula (27/29 March 1941).

After the interception and decryption of Italian signals by the Government Code and Cypher School at Bletchley Park and the very limited dissemination of the resulting 'Ultra' intelligence, Royal Navy and Royal Australian Navy ships of Admiral Sir Andrew Cunningham’s Mediterranean Fleet intercepted and sank or severely damaged several major Italian warships of Ammiraglio di Squadra Angelo Iachino’s fleet in a battle whose opening phase is known in Italy as the 'Battle of Gaudo'.

Late in March 1941, as British ships of the Mediterranean Fleet covered convoys of men, equipment and supplies to Greece, which was under Italian attack in 'Esigenza G', Mavis Batey, a cryptanalyst at Bletchley Park, made a breakthrough, reading the Italian naval 'Enigma' code for the first time. The first message, the cryptic 'Today is the day minus three' was followed three days later by a second message reporting the sailing of an Italian battle fleet of one battleship, six heavy heavy cruisers, two light cruisers and a number of destroyers to attack the merchant convoys supplying the British forces on the Italian mainland. As always with the decryption of 'Enigma' signals traffic, the resulting intelligence breakthrough was concealed from the Italians by ensuring there was a plausible, visible reason for the Allies to have detected and intercepted their fleet. In this case, it was a carefully directed reconnaissance aeroplane.

As a further deception, Cunningham made a surreptitious exit after the fall of night from a golf club in Alexandria to avoid being seen boarding his flagship, the battleship Warspite. He had made a point of arriving at the club during the afternoon with his suitcase as if for an overnight stay, and spent some time on the course within sight of the Japanese consul. An evening party on his flagship was advertised for that night, but was never meant to take place.

At the same time, there was a failure of intelligence on the Axis side. The Italians had been incorrectly informed by the Germans that the Mediterranean Fleet had only one operational battleship and no aircraft carriers. In fact this fleet possessed had three operational battleships, while the damaged aircraft carrier Illustrious had been replaced by Formidable.

Thus the Mediterranean Fleet was centred on the fleet carrier Formidable and the 'Queen Elizabeth'-class battleships Barham, Valiant and Warspite. The main fleet was accompanied by the 10^th Destroyer Flotilla (the British Greyhound and Griffin and the Australian Stuart) under the command of Commander M. L. Waller, and the 14^th Destroyer Flotilla (the British Jervis, Janus, Mohawk and Nubian) under the command of Captain P. J. Mack. Also present were the destroyers Hotspur and Havock. Force 'B', commanded by Vice Admiral H. D. Pridham-Wippell, comprised the British light cruisers Ajax, Gloucester and Orion, the Australian light cruiser Perth, and the British destroyers Hasty, Hereward and Ilex. The Australian destroyer Vendetta had returned to Alexandria. Allied warships attached to convoys were also available: the British destroyers Defender, Jaguar and Juno waited in the Kithira Channel. and the British destroyer Decoy, British light cruisers Carlisle, Calcutta and Bonaventure, and the Australian destroyer Vampire[ were also in the vicinity.

The Italian fleet was led by Iachino’s flagship, the modern battleship Vittorio Veneto, screened by the destroyers Alpino, Bersagliere, Fuciliere and Granatiere of the 13a Squadriglia Cacciatorpediniere. The fleet also included most of the Italian heavy cruiser force, namely Ammiraglio di Divisione Carlo Cattaneo’s Zara, Fiume and Pola of the 1a Divisione Incrociatori accompanied by the destroyers Alfredo Oriani, Giosuè Carducci, Vincenzo Gioberti and Vittorio Alfieri of the 9a Squadriglia Cacciatorpediniere; and Ammiraglio di Divisione Luigi Sansonetti’s heavy cruisers Trieste, Trento and Bolzano of the 3a Divisione Incrociatori accompanied by the destroyers Ascari, Corazziere and Carabiniere of the 12a Squadriglia Cacciatorpediniere. Joining these ships were Ammiraglio di Divisione Antonio Legnani’s light cruisers Luigi di Savoia Duca degli Abruzzi and Giuseppe Garibaldi of the 8a Divisione Incrociatori and the destroyers Emanuele Pessagno and Nicoloso da Recco of the 16a Squadriglia Cacciatorpediniere from Brindisi. Significantly, none of the Italian ships had radar, whereas several of the Allied ships did possess this invaluable sensor.

On 27 March, Pridham-Wippell led the cruisers Ajax, Gloucester, Orion and Perth, together with a number of destroyers, departed Greek waters for a position to the south of Crete. Cunningham departed Alexandria on the same day with Formidable, Warspite, Barham and Valiant to meet the cruiser force.

The Italian fleet was spotted by a Short Sunderland four-engined flying boat at 12.00, depriving Iachino of any advantage of surprise. As a result of the work of the decryption team on board Vittorio Veneto, the Italian admiral also learned that Formidable was at sea. Even so, after some discussion, the Italian headquarters decided to go ahead with the operation, to show the Germans their will to fight and in light of the confidence it had in the higher speed of its warships.

At 06.35 on 28 March, a Meridionali Ro.43 single-engined scouting floatplane launched by Vittorio Veneto spotted the British cruiser squadron, and at 07.55, the Trento group encountered Pridham-Wippell’s cruiser group to the south of the Greek island of Gavdos. The British squadron was heading to the south-east and, believing that they were attempting to run from their larger ships, the Italians gave chase, opening fire at 08.12 at a range of 24,060 yd (22000 m). The three heavy cruisers fired repeatedly until 08.55, with Trieste firing 132 armour-piercing rounds, Trento 204 armour-piercing and 10 high explosive shells, and Bolzano 189 armour-piercing shells, but the Italians experienced trouble with their rangefinding equipment and scored no significant hits. Gloucester fired three salvoes in return, but though these fell short they did cause the Italians to make a course change.

As they had not reduced the range significantly after one hour of pursuit, the Italian cruisers broke off the chase, turning to the north-west on a course to rejoin Vittorio Veneto. The Allied ships changed course in turn, following the Italian cruisers at extreme range. Iachino allowed the British approach in the hope of luring them within the range of Vittorio Veneto's guns.

The Italians intercepted Orion's signal that she had sighted an unknown warship and was about to investigate. At 10.55, Vittorio Veneto joined the Italian cruisers and immediately opened fire on the shadowing Allied cruisers. She fired 94 rounds in 29 salvoes from a range of 25,155 yards (23000 m), all well aimed but again with an excessive dispersal of her salvoes. (Another 11 rounds became jammed in the gun barrels.) The Allied cruisers, until then unaware of the presence of a battleship, withdrew, suffering slight damage from fragments of the 381-mm (15-in) shells.

Cunningham’s force, which had been attempting to rendezvous with Pridham-Wippell’s ships, launched an attack by Fairey Albacore single-engined torpedo bombers from Formidable at 09.38. The aircraft attacked Vittorio Veneto without direct effect, but the manoeuvring required to evade the torpedoes made it difficult for the Italian ships to maintain their pursuit. The Italian ships fired 152-, 100- and 90-mm (6-, 3.94- and 3.54-in) guns, and also 37- and 20-mm cannon as well as 13.2-mm (0.52-in) machine guns when at close range as they repelled the attack, while one of the two Junkers Ju 88 twin-engined bombers escorting the Italian fleet was shot down by a Fulmar. Iachino broke off the pursuit at 12.20, retiring towards his own air cover at Taranto.

A second British air attack at 15.09 surprised the Italians, and Lieutenant Commander J. Dalyell-Stead was able to fly his Albacore to within 1,095 yards (1000 m) of Vittorio Veneto before releasing a torpedo which hit the battleship’s outer port propeller and caused 4,000 tons of flooding. Dalyell-Stead and his crew were killed when their aeroplane was shot down by the battleship’s anti-aircraft fire. The ship stopped while the damage was repaired, but was able to get under way again at 16.42, making 19 kt. Cunningham heard of the damage to Vittorio Veneto and started a pursuit.

A third attack by six Albacore and two Swordfish aircraft of Nos 826 and 828 Naval Air Squadrons from Formidable and two Swordfish aircraft of No. 815 squadron from Crete took place between 19.36 and 19.50. Iachino deployed his ships in three columns and used smoke, searchlights and a heavy barrage to protect Vittorio Veneto. The tactic prevented further damage to the battleship, but one torpedo hit Pola, which had nearly stopped to avoid running into Fiume and could take no evasive action. This blow knocked out five boilers and the main steam line, causing Pola to lose electrical power and drift to a stop. Unaware of Cunningham’s pursuit, a squadron of cruisers and destroyers was ordered to return and help Pola. This squadron included Pola's sister ships, Zara and Fiume. The squadron did not start to return toward Pola until about one hour after Iachino’s order had been given, officially as a result of communication problems, while Vittorio Veneto and the other Italian ships continued toward Taranto.

At 20.15, Orion's radar detected a ship 6 miles (9.7 km) to port, apparently dead in the water. This was the crippled Pola. Most of the Allied force detected the Italian squadron on radar shortly after 22.00, and were able to close without being detected. The Italian ships lacked radar and could therefore detect the British ships by no means other than sight: Italian tactical thinking did not envisage night actions and their main gun batteries were not prepared for action. At 22.20 the Italians spotted the Allied squadron, but thought them to be Italian ships. The battleships Barham, Valiant and Warspite were able to close to 3,800 yards (3475 m), which was point-blank range for battleships' 15-in (381-mm) guns, at which point they opened fire. The Allied searchlights illuminated their opponent. Some British gunners saw Italian main turrets flying dozens of metres into the air. Fiume and Zara were destroyed in minutes: Fiume sank at 23.30, while Zara was finished by a torpedo from the destroyer Jervis at 02.40 of 29 March.

Two Italian destroyers, Vittorio Alfieri (flagship of the flotilla commander, Capitano di Vascello Salvatore Toscano) and Giosuè Carducci, were sunk in the first five minutes. The other two destroyers, Gioberti and Oriani, managed to escape in a smoke screen, the former with heavy damage after being chased and engaged by the British destroyers Griffin and Greyhound. Towing Pola to Alexandria as a prize was considered, but daylight was approaching, and it was thought that the danger of Axis air attack was too high. British boarding parties seized a number of much-needed Breda anti-aircraft machine guns, Pola's crew was taken off and the cruiser was then sunk by torpedoes from the destroyers Jervis and Nubian shortly after 04.00. The only known Italian reaction after the shocking surprise was a fruitless torpedo charge by Oriani and Gioberti, and the aimless fire of one of Zara's 40-mm guns in the direction of the British warships.

The Allied ships rescued Italian survivors but left the scene in the morning, fearing Axis air attack. Cunningham ordered a signal to be made on the merchant marine emergency band, and this signal was received by the Italian high command: the signal informed them that, as a result of the threat of air attack, the Allied ships had ceased their rescue operations and granted safe passage to a hospital ship for rescue purposes. The location of the remaining survivors was broadcast, and the Italian hospital ship Gradisca came to recover them. Allied casualties during the battle were a single torpedo bomber shot down by Vittorio Veneto's 90-mm (3.54-in) anti-aircraft batteries, with the loss of its three-man crew. Italian losses were up to 2,303 men, most of them from Zara and Fiume. The Allies rescued 1,015 survivors, while the Italians saved another 160.

While the 'Battle of Cape Matapan' had been described as 'Italy’s greatest defeat at sea, subtracting from its order of battle a cruiser division', it was not decisive. The British naval forces in the Mediterranean lost the heavy cruiser York and the new light cruiser Bonaventure in the same period (26/31 March), but while in the course of the war the Royal Navy lost the heavy cruisers York, Exeter, Cornwall and Dorsetshire, the latter pair in a single engagement, in the 'Battle of Cape Matapan' the Regia Marina lost three heavy cruisers in one night. That the Italians had sortied so far to the east established a potential threat that forced the British to keep their battleships ready to face another sortie during the operations off Greece and Crete.

The Italian fleet did not venture into the eastern part of the Mediterranean Sea again until the fall of Crete two months later, and it did not come out in full force until the British 'Vigorous' undertaking in the middle of June 1942. Despite his impressive victory, Cunningham was somewhat disappointed with the failure of the destroyers to make contact with Vittorio Veneto, and the fact that the Italian battleship had escaped intact was, in Cunningham’s words, 'much to be regretted'.

For reasons of secrecy, the Bletchley Park codebreakers were very rarely informed of the operational effects of their work, but their impact on the 'Battle of Cape Matapan' was an exception. A few weeks after the battle, Cunningham visited Bletchley Park to congratulate Dilly and his team, with a positive impact on morale. Rear Admiral J. C. Godfrey, the director of Naval Intelligence, stated: 'Tell Dilly that we have won a great victory in the Mediterranean and it is entirely due to his girls.'