Convoy HX 237 HX 237 was a North Atlantic convoy of the HX series which ran during the battle of the Atlantic in World War II . It was one of several convoy battles that occurred during the crisis month of May 1943 . Background . HX 237 was an east bound convoy of 47 ships , plus local contingents , which sailed from New York on 1 May 1943 bound for Liverpool and carrying war materials . Convoy commodore was Capt . R Gill RNR in " Pacific Enterprise " . Mid - Ocean Escort Force group C2 joined the convoy from St Johns on 7 May . Escort group C2 was led by Cdr EH Chavasse in destroyer " Broadway " ; other ships of this group were frigate " Lagan " and three corvettes . These were joined on the same day by a Support Group , SG 5 , comprising escort carrier " Biter " and four destroyers . Arrayed against them in the North Atlantic were the patrol lines " Rhein " , " Elbe " and " Drossel " , though although in the event only " Rhein " and " Drossel " , comprising 19 U - boats , engaged HX 237 . Action . First contact was made on 9 May by " U - 359 " , which called up other boats from " Rhein " and commenced shadowing . " U - 359 " was attacked by an escort , and lost contact , but the following day , 10 May , contact was regained by " U - 454 " . She also was driven off , by aircraft from " Biter " , but by evening a number of U - boats from both groups were in contact and began their attack . These were unable to penetrate the escort screen , though three ships that had become separated were sunk ; the Liberty ship " Fort Concord " , sunk by " U - 403 " and " U - 456 " in the early hours of 11 May ; the Norwegian tanker " Sandanger " , sunk by " U - 221 " on 12 May , and Norwegian freighter " Brand " , sunk by " U - 603 " on the night of 12 / 13 May . On 12 May " U - 89 " was sighted by a Swordfish from " Biter " and destroyed by " Broadway " and " Lagan " . Later the same day HX 237 came within range of Coastal Command aircraft , and " Biter " and her group detached to go to the aid of SC 129 , which was coming under attack 200 miles to the south - west . That night " U - 456 " was attacked by a Liberator flying at long range . The aircraft used FIDO , a new and secret homing torpedo , on the rapidly diving U - boat ; she was damaged , but was able to surface and drive off the aircraft with anti - aircraft fire . The Liberator was able to summon help , however , and the next morning the destroyer " Opportune " found " U - 456 " and attacked . The U - boat crash - dived , but was not seen again ; it was later presumed she had been fatally damaged by the aircraft attack , the first instance of a U - boat being sunk by FIDO . On 13 May " U - 753 " was found and attacked by a Sunderland , but the U - boat chose not to dive to escape , driving off the aircraft with flak . The Sunderland commenced circling and summoned help , which came in the form of " Lagan " and " Drumheller " . As " U - 753 " dived away the Sunderland attacked with depth - charges , followed by depth - charges from the two ships . Nothing more was heard from " U - 753 " and post - war analysis credited the aircraft and two ships with her destruction . With these losses , and little success in breaching the convoy ’ s defences , BdU called off the attack . HX 237 continued without further interference and arrived at Liverpool on 17 May 1943 . Aftermath . HX 237 was seen as a success by the Allies . Three ships had been lost , but 38 ships arrived safely ; another four had been forced to return and two had detached to other destinations . In return , three U - boats had been destroyed , though two of these were unconfirmed at the time . Several others had been damaged and forced to return to base . The convoy was another in a series of set - backs suffered by the U - boat Arm , collectively known as Black May .