Convoy ON 207 ON 207 was a North Atlantic convoy of the ONS / ON series which ran during the battle of the Atlantic in World War II . It was the subject of a major U - boat attack in October 1943 , the fourth battle in the German Navy ’ s ( " Kriegsmarine " KM ’ s ) autumn offensive . Background . Still believing their new weapons and tactics gave them an advantage , despite the losses suffered by wolfpack " Schlieffen " and unaware of the poor results achieved during its attack on convoys ONS 20 and ON 206 , BdU ( " Befehlshaber der Unterseeboote " , Commander of the Submarines ) re - organized the boats then in the North Atlantic into patrol line " Siegfried " to continue the offensive . The next convoy subjected to an attack was ON 207 . Protagonists . ON 207 departed Liverpool on 18 October 1943 , bound for New York . Composed of 52 ships it was escorted by Canadian escort group C - 1 , which comprised 3 destroyers ; " Forester " ( Cdr JA Burnett as Senior Officer Escort ) , " St Laurent " and " Assiniboine " , frigate " Ettrick " and 3 corvettes ; " Agassiz " , " Galt " and " Celandine " . The escort was augmented by the escort carrier " Biter " , with 3 sloops ( " Crane " , " Pheasant " and " Chanticleer " ) as escort , and the MAC carrier " Amastra " , though she had to return to base early in the voyage with storm damage . BdU had established the patrol line " Seigfried " of 18 boats . It consisted of 7 boats from the disbanded group " Schlieffen " , plus 11 others from bases in France and Germany . All the reinforcements were commanded by new skippers ; 6 from Norway were also new boats , while the 5 from France were experienced boats with new commanders . The " Siegfried " boats had fuel problems , so a re - fueling group was established north of the Azores , of 3 U - tankers and a flak boat as escort . When Allied intelligence learned of the position of " Seigfried " , it was decided to force an engagement with the wolfpack ; several HX and SC convoys in the area were diverted away , whilst ON 207 was left to continue on course , as a bait convoy for the U - boats . ON 207 was massively reinforced by two support groups , 2nd EG commanded by Capt FJ Walker , and B - 7 EG , commanded by Cdr P Gretton , which detached from a successful trip with ON 206 . 2 EG comprised 4 sloops ( " Starling " , " Magpie " , " Wild Goose " and " Woodcock " ) and was accompanied by the escort carrier " Tracker " . ( Two of 2EG ' s sloops were absent at the time ) . B 7 group at this point comprised 2 destroyers ( " Duncan " and " Vidette " ) , and 2 corvettes ( " Loosestrife " and " Sunflower " ) . B - 7 also had 2 corvettes detached . The Action . On 23 October 1943 " U - 274 " was sighted by an air patrol , a Liberator of 224 squadron RAF , attempting to make contact with the convoy . The Liberator attacked , and was joined by escorts " Vidette " and " Duncan " of B - 7 . They also attacked with depth charges , and " U - 274 " was destroyed with all hands . On 26th " U - 91 " was attacked by a Liberator of 10 sqdn RCAF , but she escaped with little damage . Later in the day , another Liberator of 10 sqdn attacked and destroyed " U - 420 " . On 29th B 7 detached to join ON 208 , which was following several days behind ; the group found " U - 282 " shadowing the convoy . " Duncan " , " Vidette " and " Sunflower " attacked with depth charge and Hedgehog , and " U - 282 " was destroyed with all hands . During the time ON 207 was in " Siegfried " s patrol area , none of its boats were able to launch an attack , and none of ON 207s ships were harmed by enemy action . While this action was taking place , " Seigfried " ’ s refuelling group was also under attack , from two USN Hunter - killer groups centred on the escort carriers " Block Island " and " Card " . On the night of 25 / 26 October they attacked the U - tanker " U - 488 " , though she escaped with no damage ; on 28th they attacked two U - boats , " U - 220 " , which was destroyed , and " U - 256 " which was damaged and forced to return to base . On 31st two more boats were attacked , " U - 91 " which escaped again , and " U - 584 " , which was destroyed . Later that day destroyer " Borie " destroyed " U - 405 " in a 72 minute duel , that also saw " Borie " fatally damaged , sinking later that day . ON 207 continued to its destination , arriving at New York on 4 November 1943 . Conclusion . With 3 U - boats destroyed for no ships lost ON 207 was undoubtedly an Allied victory ; but if Admiralty was hoping to inflict a crushing blow to UbW by wiping out an entire wolf pack , this success eluded them . Most of the U - boats were unable to make contact , and those that did were unable to shadow effectively in order to bring the pack together . Possibly the escorts were unfamiliar with their role as bait , and were too efficient at keeping the pack away from the convoy . Following ON 207 BdU re - configured " Siegfried " to form 3 sub - groups to cover a wider area , but this failed to produce results . Also BdU was realizing that the new weapons and tactics underpinning the Autumn offensive were not being successful ; and following the attack on ON 207 no further North Atlantic convoys were seriously harmed . Table . U - boats destroyed