Convoys ONS 20/ON 206
Part ofWorld War II
Date 15–18 October 1943 Location North Atlantic Result Allied victory
Belligerents
Germany	United Kingdom  Canada
Commanders and leaders
AdmiralKarl Dönitz	ONS 20 : Comm: Escort :Cdr HR Paramor ON 206 : Comm : Escort :Cdr RA Currie
Strength
Schlieffen: 14 U-boats	ONS 20: 52 ships 6 escortsON 206 : 62 ships 5 escorts Support group B7 : 7 warships
Casualties and losses
6 U-boats destroyed	1 ship sunk

ONS 20 andON 206 wereNorth Atlanticconvoys of theONS/ON series which ran during thebattle of the Atlantic inWorld War II.They were the subject of a major U-boat attack in October 1943, the third battle in theKriegsmarine's autumn offensive.

Despite the losses suffered byRossbach and poor results achieved during its attack onSC 143, andstill believing their new weapons and tactics gave them an advantage, BdU (Befehlshaber der Unterseeboote Commander of the Submarines) re-organized the boats then in the North Atlantic into patrol lineSchlieffen with the intention of intercepting the expected west-bound convoys. These were ONS 20 and ON 206.

ONS 20 departed Liverpool on 9 October 1943.Composed of 52 ships it was bound for Halifax, and was escorted by B-4 escort group, which comprised 6destroyer escorts led byHMSBentinck (Cdr HR Paramor as Senior Officer Escort).

ON 206 departed Liverpool on 11 October 1943;Composed of 62 ships, mainly in ballast, it was bound for New York and was escorted byB-6 escort group, comprising 2destroyers,Fame (Cdr RA Currie SOE) andVanquisher, thefrigateDeveron, and 3corvettes.

Also in the vicinity was Escort groupB-7, in the role of a support group; it comprised 2 destroyers,Duncan (Cdr P Gretton) andVidette, and 4 corvettes.

GroupSchlieffen comprised a number of U-boats from groupRossbach, re-inforced by newcomers from bases inFrance andGermany. It had already come under attack whilst re-fueling by aircraft from USSCard; one boat was damaged and forced to retire, and 2 boats (U-402 andU-603 ) had been sunk. Another 2 boats had collided, and one of these was also forced to return to base for repair.At the time of the attack on convoysSchlieffen consisted of 14 boats, with a mix of experience and type.

When Allied intelligence learned of the position ofSchlieffen,Western Approaches Command decided to seek battle, increasing the defence by joining the two convoys and their escorts, and sending B-7 as reinforcement.

On 15 October 1943 the convoys were sighted byU-844, and groupSchlieffen was direct to converge on the position. By evening a number of boats were in position and commenced the attack, which became one of the most calamitous of the entire campaign for theU-boat Arm (U-Bootwaffe, UBW). During the night of 15/16 October the U-boats attacked but were repulsed;U-844 was damaged byDuncan andVanquisher and driven off. Later on 16 OctoberU-844 was attacked and sunk by twoLiberators from86 Squadron and59 Squadron (Royal Air Force); one Liberator was shot down and the crew was rescued by the corvettePink.U-964 was sunk by a Liberator of 86 Squadron; her survivors were later picked up byU-231. Early that dayU-470 was damaged by aSunderland of422 Squadron (Royal Canadian Air Force); the Sunderland was also damaged, ditching later near the ships of ONS 20 and its crew was rescued by HMSDrury. Later,U-470 was attacked again by two Liberators from RAF120 Squadron and another from 59 Squadron and sunk; two of her crew were picked up byDuncan. The only success for theSchlieffen boats that day was whenU-426 sank the freighterEssex Lance, which was straggling from ONS 20.

During the night of 16/17 October the attack was renewed but repulsed with no success;U-540 was attacked and damaged by a Liberator of 59 Squadron; later that day she was attacked again and sunk by two Liberators from 59 and 120 squadrons. Also on 17 October U-841 was sunk byByard of B-4 Group. During the night of 17/18 October the shadowerU-631 was sunk byHMS Sunflower of B-7 Group. The convoys made a drastic alteration in course, to shake off any shadowers; this was successful in that BdU received conflicting reports from U-91 and U-413, leading toSchlieffen being sent in the wrong direction.Schlieffen was unable to re-gain contact and in view of the losses sustained BdU ordered the group to retire. On 20 October, with no further attack developing, B-7 Group detached from the convoys to joinON 207, which was following; ONS 20 was handed over to its Western Local Escort Group on 22 October and arrived at Halifax without further loss on 26 October 1943. ON 206 met its Local Escort Group on 24 October and arrived at New York on 27 October 1943.

BdU regarded this operation as a setback but remained confident that their new weapons and tactics would achieve success. The loss of six U-boats for the sinking of one ship was a big defeat for the UbW and is seen as a victory for the Allies.

Allied ships sunk

Axis submarines destroyed

• List of shipwrecks in October 1943

• Clay, Blair (2000) [1998].Hitler's U-Boat War: The Hunted 1942–1945. Vol. II (pbk. repr. Cassell, London ed.). New York: Random House.ISBN 0-304-35261-6.
• Peter Gretton : Convoy Escort Commander (1964) ISBN (none)
• Arnold Hague :The Allied Convoy System 1939–1945 (2000) ISBN (Canada) 1 55125 033 0 : ISBN (UK) 1 86176 147 3
• Kemp, Paul (1997).U-Boats Destroyed, German submarine losses in the World Wars. Arms and Armour.ISBN 1-85409-515-3.
• Niestle, Axel (1998).German U-Boat Losses During World War II. Greenhill.ISBN 1-85367-352-8.
• Stephen Roskill :The War at Sea 1939–1945 Vol III (1960) ISBN (none)
• Jak P M ShowellU-Boat Warfare: The Evolution of the Wolf-Pack (2002)ISBN 0-7110-2887-7

• ONS 20 on convoyweb
• ON 206 on convoyweb

• North Atlantic convoys of World War II
• Naval battles of World War II involving the United Kingdom

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