This was an Allied programme of naval measures, the maritime counterpart of 'Flax', against the Axis shipping involved in the attempted withdrawal of the German and Italian land forces from Tunisia (7/13 May 1943).
The operation was codenamed 'Retribution' specifically to recognise the losses which the Mediterranean Fleet’s cruisers, destroyers and smaller warships, as well as merchant marine vessels, had suffered during the naval undertakings to evacuate the British and allied forces from Greece and Crete in the aftermath of 'Marita' and 'Merkur'.
Undertaken at the end of the North African campaign, the operation was controlled by Admiral Sir Andrew Cunningham, the Allied naval commander-in-chief in the Mediterranean, who used a force of 18 British destroyers and a number of Malta-based coastal flotillas to intercept Italian surface forces attempting any evacuation of the Axis powers’ crumbling lodgement in Tunisia.
The predicament of the Axis forces in Tunisia had been recognised as the Allies prepared an implemented their 'Vulcan' final offensive in Tunisia, and expected that the Axis commands would attempt a major effort to evacuate their personnel. Thus all available naval light forces were ordered to concentrate at Malta or Bône and then to patrol specified areas. In order to achieve this, convoy movements were restricted to release their escorts. It was also expected that the Italian fleet would try to intervene, so the battleships Nelson and Rodney, together with the fleet carrier Formidable, were moved to Algiers in readiness for commitment in a major action.
As it was, the Italian fleet did not leave port and there was no organised attempt to evacuate Axis forces by sea. Two supply ships en route to Tunisia were intercepted and sunk, and the craft of British motor torpedo boat and US PT-boat flotillas intercepted a number of small craft and also raided the waters around Ras Idda and Kelibia.
The only significant threat to the sea forces was 'friendly fire' attacks by Allied aircraft: after three destroyers had been damaged by such air attacks, Cunningham ordered that their upperworks should be painted red as an identifying mark.
During this interdiction of the passage between Tunisia and Sicily, the Allies captured 897 men, 653 Germans are thought to have escaped to Italy, and an unknown number were drowned.
The Axis forces in North Africa, squeezed into an ever smaller area with minimal supplies and facing well-supplied opponents, surrendered on 13 May. The North African ports were rapidly cleared and readied to support the planned invasions of southern Europe. The 12th, 13th and 14th Minesweeping Flotillas from Malta, two groups of minesweeping trawlers and smaller vessels cleared a channel through the minefields of the Sicilian Channel to Tripoli, removing nearly 200 moored mines.
On 15 May, Cunningham was able to signal that with the passage through the Mediterranean now cleared, convoys from Gibraltar to Alexandria could be resumed. Thus the direct route between Gibraltar and Alexandria, which had been closed since May 1941, was reopened, resulting in huge savings of merchant shipping and its naval escorts, which had been compelled to make the long passage round the Cape of Good Hope at great expense in fuel, wear and tear, and time.