'Grog' (i) was British naval undertaking against the north-west coast of Italy, in which Genoa was shelled in a repeat of the cancelled 'Result', Livorno was subjected to an attack by aircraft of the fleet carrier Ark Royal, and the approaches to La Spezia were mined (6/11 February 1941).
For this undertaking, Vice Admiral Sir James Somerville’s Force 'H' departed Gibraltar in three groups. Group 1 comprised the battleship Malaya, the battle-cruiser Renown, the fleet carrier Ark Royal and the light cruiser Sheffield; Group 2 comprised the destroyers Encounter, Fearless, Foxhound, Foresight, Fury and Jersey; and Group 3 comprised the destroyers Duncan, Firedrake, Isis and Jupiter.
Groups 1 and 2 departed Gibraltar initially as decoys shortly after the westbound HG.53 convoy and headed out into the Atlantic, but reversed course in the night and passed through the Strait of Gibraltar on an easterly course. Group 3 had meanwhile headed to the east out of Gibraltar and conducted anti-submarine operations along the expected course of Force 'H' before linking with the other two groups.
On 8 February an intercepted transmission from a carrierborne aeroplane to the south of the Balearic islands group led the Supermarina (Italian admiralty) to believe that the British were attempting to pass an eastward convoy to Malta, and this persuaded the Italian command authority to despatch Ammiraglio di Squadra Angelo Iachino’s main Italian fleet with the battleships Vittorio Veneto, Andrea Doria and Giulio Cesare, together with eight destroyers, from La Spezia, and the heavy cruisers Trieste, Trento and Bolzano, together with two destroyers, from Messina with orders to join forces during the evening of 9 February in an area to the north-west of Sardinia.
To add further deception, Force 'H' shaped an easterly course toward Sardinia after daybreak on 8 February. In the morning of 9 February Malaya, Renown and Sheffield arrived off Genoa and fired 273 15-in (381-in), 782 6-in (152-mm) and 400 4.5-in (114-mm) shells into the city’s port area and other naval and military targets. In the harbour there were 55 ships, and the bombardment sank four freighters and an old training ship, damaged 18 other ships with near misses and shell splinters, sank 14 lighters and killed 144 persons as well as wounding another 272 persons. There was also severe damage in the city. The docked battleship Caio Duilio was not damaged.
During the bombardment the Italian coastal batteries responded, but achieved no hits as the visibility was too poor for accurate fire on moving targets.
At the same time Ark Royal and three destroyers were operating independently in a carrierborne air attack on Livorno: 14 Fairey Swordfish bombers mined La Spezia harbour and bombed an oil refinery in Livorno. Two Italian reconnaissance aircraft tried to shadow the retiring British forces, but were short down by Fairey Fulmar carrierborne fighters.
Meanwhile the Italian fleet, informed of events to the north, turned back from the Strait of Bonifacio, separating Corsica and Sardinia, in an attempt to intercept the British forces. The Italian effort was stymied by a number of factors including fog, which prevented reconnaissance aircraft from spotting Somerville’s vessels. Force 'H' thus returned safely to Gibraltar on 11 February.