This was a British naval undertaking off the coast of north-western Italy by Vice Admiral Sir James Somerville’s Gibraltar-based Force ‘H’ to mine the approaches to Livorno (17/30 August 1941).
Aided by diversions such as a carrierborne air attack, using incendiary bombs, against the cork forest outside Tempio Pausania in northern Sardinia and a surface force demonstration off Valencia on the east coast of Spain, the operation used the cruiser minelayer Manxman disguised as a French ‘Léopard’ class large destroyer between the time she sailed from the UK and returned, except for the period in which she laid her mines on 25 August, and was also used to provide cover for the return of two of the transport vessels of the GM.1 convoy.
The 10,891-ton fast freighter Durham departed Malta after dark on 21 August and, despite suffering mine damage forward, reached Gibraltar on 24 August. The 9,513-ton freighter Deucalion sailed on 26 August, accompanied by the escort destroyer Farndale which had been detained at Malta with mechanical problems, and both ships arrived safely at Gibraltar on 26 August.
A diversion for this operation was provided by the battleship Nelson, fleet carrier Ark Royal, light anti-aircraft cruiser Hermione and destroyers Encounter, Foresight, Forester, Fury and Nestor, which made a diversionary sweep off the coast of Valencia in eastern Spain and then flew carrierborne air attacks against the cork forest outside Tempio on the Italian island of Sardinia.
The departure of Force ‘H’ from Gibraltar was reported by Italian agents at Algeciras in neutral Spain, and allowed the Italian navy to consider a number of options. On 23 August the Italian navy’s 9a Divisione Navi di Battaglia, under the command of Ammiraglio di Squadra Angelo Iachino and comprising the battleships Littorio and Vittorio Veneto, escorted by five destroyers, sortied for an attack on a British convoy and joined forces at a location to the east of Sardinia with the 3a Divisione Incrociatori (heavy cruisers Bolzano, Gorizia, Trento and Trieste), which had sortied from Messina with 14 destroyers (four escorting the cruisers and the other 10 in other detachments). On the following day the Italian forces moved into the area to the south of Sardinia, where they were assured of Italian air cover, as distant cover for the planned attack on the Malta convoy, which was to be delivered by the ships of the 8a Divisione Incrociatori (light cruisers Luigi di Savoia Duca degli Abruzzi, Muzio Attendolo and Raimondo Montecuccoli) supported by another five destroyers despatched from Palermo to operate in the waters north of Tunisia.
To the south-west of Sardinia the submarines Alagi, Serpente, Aradam and Diaspro were on patrol, and in the Sicilian Narrows were the submarines Squalo, Fratelli Bandiera, Tricheco, Topazio and Zaffiro as well as 13 MAS motor torpedo boats.
None of these Italian groupings detected the British warships, whose approach to their target area was made to the east of the Balearic Islands and then to the north-east. There were several British submarines operating in the area between between Sardinia and Sicily as well as in the Strait of Messina, and of these Upholder discovered and reported the Italian fleet before delivering an unsuccessful attack on the light cruiser Luigi di Savoia Duca degli Abruzzi.
On the same day Manxman laid 70 magnetic mines and 70 moored mines off Livorno, and 10 Fairey Swordfish carrierborne bombers attacked the airfield outside Tempio Pausania. Their tasks accomplished, the British ships then turned back to Gibraltar, still without being discovered by the Italians. Iachino’s forces were still searching for the convoy heading for Malta, but turned for home on 25 August.
To the north of Messina the British submarine Triumph torpedoed and severely damaged the cruiser Bolzano.