'Gibbon' was the Allied transfer of the Italian fleet to British control as one of the terms of the Allied armistice with Italy (9/10 September 1943).

When, during the afternoon of 8 September General Dwight D. Eisenhower, the Supreme Commander Allied Force of the North African Theatre of Operations, announced the armistice between the Allies and Italy, the Germans launched their pre-planned 'Achse' (ii) to seize as much of Italy as they could and also to disarm the Italian forces.

However, in accordance with the terms of the armistice, Ammiraglio di Armata Carlo Bergamini’s Italian fleet departed La Spezia with the battleships Roma, Vittorio Veneto and Italia (Ammiraglio di Divisione Marchese Enrico Accoretti’s 9a Divisione Navi di Battaglia), the light cruisers Eugenio di Savoia, Emanuele Filiberto Duca d’Aosta and Raimondo Montecuccoli (Ammiraglio di Divisione Romeo Oliva’s 7a Divisione Incrociatori), and the destroyers Mitragliere, Fuciliere, Carabiniere and Velite (Capitano di Vascello Marini’s 12a Flottiglia Cacciatorpediniere) and Legionario, Alfredo Oriani, Artigliere and Grecale (Capitano di Vascello Baldo’s 14a Flottiglia Cacciatorpediniere) and joined the light cruisers Luigi di Savoia Duca degli Abruzzi, Giuseppe Garibaldi and Attilio Regolo (Ammiraglio di Squadra Luigi Bianchieri’s 8a Divisione Incrociatori) as well as the torpedo boat Libra from Genoa.

The combined force was located by German reconnaissance aircraft and came under attack to the west of the Strait of Bonifacio during the afternoon of 9 September by 11 Dornier Do 217 bombers of Hauptmann Bernhard Joppe’s III/Kampfgeschwader 100, a specialist anti-shipping unit using FX-1400 'Fritz X' radio-controlled armour-piercing bombs, from Istres near Marseille. One Do 217 scored two direct hits on Roma, which sank, and Italia (ex-Littorio) was damaged by another hit. The destroyers Antonio da Noli and Ugolino Vivaldi, coming from Castellamare, were shelled by German coastal batteries in the Strait of Bonifacio and lost to mines and gunfire respectively, the crew of Ugolino Vivaldi being rescued by the British submarine Sportsman. Attilio Regolo, Mitragliere, Fuciliere and Carabiniere were detached to rescue survivors, and the torpedo boats Libra, Orione, Orsa, Impetuoso and Pegaso were also called to the scene: Libra and Orione then steamed to Bône, and the others reached Port Mahon in the Spanish Balearic islands where they were interned, though Pegaso and Impetuoso sank after colliding just outside the harbour.

The rest of the Italian fleet steamed toward Malta under Oliva’s command, and was met on 10 September off Bône by a detachment of Vice Admiral A. U. Willis’s Force 'H' (British battleships Warspite and Valiant and the destroyers Echo, Faulknor, Fury, Intrepid, Raider, Free French Terrible and Free Greek Vasilissa Olga).

On 9 September Ammiraglio di Squadra Alberto da Zara departed Taranto with the battleships Andrea Doria and Caio Duilio (5a Divisione Navi di Battaglia), the light cruisers Luigi Cadorna and Pompeo Magno, and the destroyer Nicoloso da Recco, and these ships reached Malta on 10 September escorted by the battleship King George V.

In addition, the battleship Giulio Cesare, seaplane tender Giuseppe Miraglia, destroyer Riboty and torpedo boat Sagittario reached Malta from Adriatic ports.

Some 33 serviceable Italian submarines, which were concentrated off Salerno in expectation of the Allied 'Avalanche' landing or were in Italian harbours, also made their way to Allied-held harbours. By 12 September 11 torpedo boats, eight corvettes and smaller craft reached Palermo on the north coast of Allied-controlled Sicily from harbours in the Tyrrhenian Sea. At the same time 101 Italian merchant vessels were surrendered, while another 168 were scuttled to avoid seizure by the Germans.