Convoy SC 143 SC 143 was a North Atlantic convoy of the SC series which ran during the battle of the Atlantic in World War II . It was the second battle in the German Navy ’ s ( ’ ’ Kriegsmarine ’ ’ ) ( KM ) ’ s autumn offensive in the North Atlantic . Background . Following the attack on convoys ONS 18 and ON 202 by the wolfpack " Leuthen " , U - boat Control ( " Befehlshaber der Unterseeboote " , BdU ) was convinced of success and eager to continue the offensive . Accordingly they re - organized the boats then in the North Atlantic into a new patrol line , the 12 remaining " Leuthen " boats being joined by 9 new - comers , from bases in France and Germany . Code - named " Rossbach " , the group was stationed at the western edge of the Greenland Air Gap to intercept the expected east - bound convoys , carrying materiel for the invasion of Europe . For their part , the Allies were also encouraged by the outcome of the battle for ONS 18 / ON 202 , and were keen to seek battle with group " Rossbach " . While forming , " Rossbach " came under attack by air patrols ; 4 boats were destroyed , and another 4 were damaged and forced to return to base . 3 others were damaged , but were able to continue operations , while a further 2 boats arrived from base as re - inforcement . Protagonists . SC 143 left Halifax on 28 September 1943 bound for Liverpool It was composed of 39 ships and was escorted by C - 2 escort group comprising the destroyer " Icarus " , frigate " Duckworth " and 5 corvettes . Also accompanying the convoy was the MAC carrier " Rapana " . By 6 October " Rossbach " , comprising 14 U - boats at this point , was deployed to intercept the expected west - bound convoys , HX 259 and SC 143 . Western Approaches Command became aware of " Rossbach " ’ s position via intelligence , principally Enigma decrypts , but decided to engage the wolfpack and force a battle . Diverting HX 259 to the south , SC 143 was reinforced with 10th Support Group , of 4 destroyers , " Musketeer " , " Oribi " , " Orkan " and " Orwell " , and allowed to continue towards " Rossbach " as bait . Action . SC 143 was sighted on 8 October by " U - 731 " , which was returning to base following an air attack ; she sent a sighting report , and throughout the day the " Rossbach " boats converged on the position . 7 boats had gathered by evening , and at nightfall mounted their attack . During the night of 8 / 9 October the 7 " Rossbach " boats were able to attack ; " U - 645 " torpedoed and sank " Yorkmar " , and " U - 378 " hit " Orkan " which sank with the loss of 157 men . This was the worst naval loss suffered by the Polish Navy during the war . During the day the convoys air cover was able to mount several successful attacks ; 3 U - boats were attacked by aircraft during the day . " U - 419 " was attacked and sunk by a Liberator from RAF 86 Squadron ; " U - 643 " was damaged by 2 other Liberators , from RAF 86 Sqdn and RAF 120 Sqdn ; it was later caught on the surface by another Liberator of RAF 86 Sqdn and sunk . " U - 610 " was attacked by a Sunderland from RCAF 423 Sqdn and sunk . 2 other boats were damaged in air attacks and forced to return to base ; " U - 539 " by an unidentified aircraft , and " U - 762 " by a Liberator of RAF 120 Sqdn . Following this the attack was discontinued by BdU and " Rossbach " , now reduced to 6 boats , was disbanded . SC 143 continued its voyage , and arrived without further loss at Liverpool on 12 October 1943 . Conclusion . Un - deterred by the poor result of this attack , and the losses suffered by " Rossbach " , BdU wished to press on with the offensive ; the remaining " Rossbach " boats were re - inforced to form a new group code - named " Schlieffen " . Tables . Allied ships sunk Allied warships sunk Axis submarines destroyed