The U-Boats versus Convoy SC121

On March 6, 1943, 59 ships formed up as SC121 and sailed out of Sydney, Breton Island in Canada, bound for Liverpool UK.

This large convoy was escorted by a threadbare escort comprising the US cutter Spencer, the US destroyer Greer, British corvettes Dauphin, Dianthus, and Canadian corvettes Rosthern, and Trillum.

Three of these escorts had defective Sonar and a further three inoperative Radar.

All in all, a poor escort for so many ships, who needed protection from U-Boat attacks as they are sheperded across the North Atlantic ocean, one of the nastiest pieces of storm swept water in the world.


U-Boat Patrol lines await, Wolfpack Westmark with 17 boats and Wolfpack Ostmark with 9 boats.

The Wolfpack Westmark of 17 boats:

U-228 (Kptlt. Christophersen), U-230 (Kptlt. Siegmann) *, U-332 (Oblt. Hüttemann), U-359 (Oblt. Förster), U-405 (Korvkpt. Hopmann) *, U-409 (Oblt. Massmann) *, U-432 (Kptlt. Eckhardt), U-448 (Oblt. Dauter), U-523 (Kptlt. Pietzsch), U-526 (Kptlt. Möglich) *, U-527 (Kptlt. Uhlig) *, U-566 (Kptlt. Hornkohl), U-591 (Kptlt. Zetsche) *, U-616 (Oblt. Koitschka) *, U-634 (Oblt. Dalhaus), U-659 (Kptlt. Stock), U-709 (Oblt. Weber)

The Wolfpack Ostmark of 9 boats:

U-190 (Kptlt. Wintermeyer) *, U-229 (Oblt. Schetelig) *, U-439 (Oblt. Tippelskirch), U-447 (Kptlt. Bothe), U-530 (Kptlt. Lange) *, U-618 (Kptlt. Baberg), U-641 (Kptlt. Rendtel), U-642 (Kptlt. Brünning) *, U-665 (Oblt. Haupt)

* U-boats that fired torpedo or used the deck gun.

At first the convoy avoided these two Patrol lines,but it was sighted by U-405, and when Bdu received this intelligence it set up Patrol Lines Ostmark and on March 8 Westmark.

Due to the bad weather the convoy had many stragglers and its A3 escort was in bad shape when it became the escort of Convoy SC121 after just a few days of the disaster of Convoy ON 166 who had 14 ships sunk by attacking U-Boats.

Becoming aware of the U-Boat build up the Escort Commander sent out his fast escorts towards the HF/DF contacts. Just before nightfall a change of course was ordered, trying to Shake off the U-Boats, but U-556 and U-230 made contact with SC121 sinking one ship.

In the heavy gale conditions the loss of this ship went largely unnoticed, one merchant ship did recover survivors, but became straggler to be picked off by U-591 on March 7th.

Five U-Boats maintained contact and four of these each sank a straggler.

On the the 9th. Of March the ocean escort was added to by the Cutters Bibb and Ingham plus the Destroyer Babbitt and air cover came from Squadron 120.

They drive off the contact keeper U-566, and repulse six more U-Boats preparing to attack at night.

During the evening of March 9, U-503 disposes of a straggler, U-405 and U-409 attack at night and sink three more ships.

U-229 sinks one ship and damages another.

The weather again deteriorates on the10th. Five U-Boats are still able to remain in contact with SC121, U-229 and U-616 attack but fail, and then lose contact with the convoy.

Further escorts reinforce the convoy with British Corvettes Campion and Mallow.

Come March 11 the battered convoy limped into Liverpool.

Too few escorts caused SC121 to lose fourteen ships with one more damaged, I.e., 23.7% of the total coming in at 56,248 tons are sunk with a further ship of 3,670 Tons damaged.

After two more convoys are badly mauled by Wolfpacks, Churchill at last comes to the realisation that if convoys are to cross the North Atlantic Ocean both East and West in safety, he must increase the escorts that guard them.


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