'Hats' was a British naval undertaking by Vice Admiral Sir James Somerville’s Force 'H' to deliver supplies from Gibraltar to Malta and to reinforce Admiral Sir Andrew Cunningham’s Mediterranean Fleet at the eastern end of the Mediterranean (30 August/5 September 1940).

The operation was undertaken in concert with the MF.2 convoy and its 'MB' (iii) naval support despatched from Alexandria to Malta. 'Hats' was therefore one of a series of complex operations carried out by the Royal Navy after the entry of Italy into World War II had effectively split the Mediterranean Fleet into two as Cunningham’s Mediterranean Fleet based in the east at Alexandria in Egypt and Somerville’s Force 'H' based in the west at Gibraltar.

There were several objectives for 'Hats', these including the reinforcement of the Mediterranean Fleet with the new fleet carrier Illustrious, the modernised battleship Valiant, the light anti-aircraft cruisers Coventry and Calcutta, and the destroyers Gallant, Greyhound, Griffin and Hotspur (Force 'F' bound for Alexandria), the delivery of supplies to Malta, and the launching of the 'Smash' (i) and 'Grab' attacks on the airfield at Elmas and power station at Cagliari on the southern end of Sardinia by carrierborne aircraft Force 'H', and an air attack on Rhodes by carrierborne aircraft of the Mediterranean Fleet.

Prime Minister Winston Churchill had also hoped to take this chance to move a number of infantry tanks to Egypt, but this idea was strongly opposed by all relevant naval authorities and gained no support from General Sir Archibald Wavell, the commander-in-chief in the Middle East, and was abandoned. It is worth noting that later in the same year, merchant ships were safely passed through the Mediterranean as part of 'Collar', suggesting that the Admiralty had overestimated the danger from Italian air power.

The operation began on 30 August, when Force 'H' departed Gibraltar and the Mediterranean Fleet departed Alexandria. At this time Force 'H' was the core of the largest British fleet to enter the Mediterranean since the start of the war with Italy, and comprised the fleet carrier Ark Royal, the battle-cruiser Renown, the light cruiser Sheffield, and the destroyers Encounter, Faulknor, Firedrake, Foresight, Forester, Fortune and Fury supporting Force 'F' heading for Malta and Alexandria, the destroyers Velox and Wishart to carry out the 'Squawk' radio deception operation to the north of the Balearic islands to suggest that Force 'H' was planning an assault on Genoa, and the destroyers Hero, Janus, Mohawk and Nubian (Force 'A' detached from the Mediterranean Fleet to reinforce Force 'H' in escorting Force 'F').

The first contact with the Italians came on 31 August, when Blackburn Skua warplanes from Ark Royal shot down two Italian floatplanes. At 21.50 on 31 August the destroyers Velox and Wishart were detached to the north-east in 'Squawk'. The main fleet then turned to the south-east in the direction of Cagliari. At 03.25 on 1 September nine Fairey Swordfish flew off Ark Royal from a position 115 miles (185 km) from Cagliari, attacked Cagliari at 06.00 in 'Smash' and returned to the carrier by 08.00. Somerville then made a second change of direction, this time south-west in an attempt to convince the Italians he was heading back to Gibraltar. This deception measure apparently had no effect, as the Italians were not then shadowing the fleet.

At 10.30 Somerville turned back to the east and shaped course toward the Sicilian Narrows. At 22.00 on 1 September, half way between the south-eastern tip of Sardinia and the western tip of Sicily, Somerville divided his strength into two. Force 'H' turned north, in preparation for a second attack on Cagliari ('Grab' attempted on 2 September but foiled by haze and low cloud), while Cunningham’s reinforcements (Force 'F') continued to the south-east, heading for Malta and their rendezvous with the Mediterranean Fleet.

Force 'H' returned to Gibraltar early on 3 September.

At the other end of the Mediterranean, the Mediterranean Fleet departed Alexandria with the battleships Warspite and Malaya, the fleet carrier Eagle, the light cruisers Orion and Australian Sydney, and the destroyers Decoy, Defender, Hereward, Imperial, Australian Stuart, Vampire and Vendetta, and Polish Garland.

This fleet was sighted at 14.30 by a Cant Z.510 reconnaissance floatplane, which was soon shot down, but a second aeroplane was later heard overhead and escaped intact. On 31 August, off the south coast of Greece, Cunningham was joined by Vice Admiral J. C. Tovey, second-in-command of the Mediterranean Fleet, with the 3^rd Cruiser Squadron (heavy cruiser Kent and light cruisers Gloucester and Liverpool).

On 31 August the Italians had sortied from Taranto and Messina with five battleships (including the new Littorio and Vittorio Veneto), 13 heavy and light cruisers, and 39 destroyers. For lack of adequate air reconnaissance, the Italians were unable to locate any of the British forces, and turned back prematurely.

The British ships were also not discovered by any of the Italian submarines on patrol in the relevant areas: these boats comprised Corallo and Sirena to the south of Crete, and Berillo, Pier Capponi and Durbo off Malta.

On the same day, 31 August, a convoy of three British merchant ships (10,605-ton Cornwall, 5,916-ton Plumleaf and 1,587-ton Volo), with a weak escort of the destroyers Dainty, Diamond, Jervis and Juno, heading toward Malta with 36,000 tons of supplies, was attacked by Italian aircraft and Cornwall became the only British ship to suffer serious damage during this complex of operations, although the ship nonetheless reached Malta.

At about the same time one of Eagle's aircraft discovered part the Italian battle fleet, reported as two battleships and seven cruisers, 180 miles (290 km) from Cunningham’s current position. Cunningham’s natural instinct was to head for the Italian fleet in the hope of securing a major fleet action, but on the next day the Italian ships were sighted heading for Taranto and home.

At 08.00 on 2 September the Mediterranean Fleet sighted Valiant, and the halves of the operation finally came together. Valiant, Coventry and Calcutta were each carrying supplies for Malta, and so while the main strength of the Mediterranean Fleet waited 35 miles (55 km) to the south of Malta, these three ships sailed into the Grand Harbour. Among the supplies they were carrying were eight 3.7-in (94-mm) anti-aircraft guns, predictors and height-finders to support the anti-aircraft guns, replacement gun barrels, 10,000 rounds of Bofors ammunition, 100 light machine guns, and mail. Two air raids hit Malta while the ships were unloading, but by 19.00 the three warships were able to leave Malta.

Rather than return directly to Egypt, Cunningham decided to attack the Italian airfields on Rhodes. At this date the Aegean Sea was still relatively safe for British ships, and so the fleet was able to sail to the north of Crete, collecting a convoy on the way. Early on 4 September Swordfish bombers from Illustrious attacked the Italian airfields at Maritiza and Callato, while Sydney bombarded the island of Kárpathos (known to its Italian occupiers as Scarpanto) between Rhodes and Crete.

The operation ended on 5 September when the Mediterranean Fleet reached Alexandria. 'Hats' was one of a number of occasions during 1940 when the presence of a British carrier convinced a potentially strong Italian fleet not to risk combat, and played a part in reducing the effectiveness of the otherwise powerful Italian fleet.