Convoy SC 100

Convoy SC 100 was a North Atlantic convoy, one of the SC series which ran during the battle of the Atlantic in World War II. It was the 100th of the numbered series of slow convoys of merchant ships from Sydney, Cape Breton Island to Liverpool. It came under attack, one of several convoy battles that occurred during the autumn and winter of 1942, losing five ships.

Background
SC 100, comprised twenty six merchant ships and deoarted Halifax for the UK under local escort on 12 September 1942. The Convoy Commodore was Capt. NH Gale in Athelsultan. SC 100 was met by its Ocean Escort, Group A-3, led by US Coast Guard cutter USCGC Campbell (WPG-32), under Cdr. P Heineman. Also in the group was the cutter USCGC Spencer (WPG-36) and four RCN corvettes. A-3 was joined by the corvette HMCS Trillium (K172), escorting ships from Wabana, and by three corvettes travelling in convoy for refit in the UK. During the action SC 100 was joined by several units as re-inforcement, including the newly formed convoy support group, 20EG, led by Comm. FJ Walker.

SC 100 was attacked by units of two U-boat patrol lines, Lohs, of 18 boats, and Pfiel, of 11 Uboats, under the guidance of U-boat Commander (BdU) Adm K Dönitz.

Action
The convoy departed Halifax on 12 September 1942 and was joined on 16 September by Mid-Ocean Escort Force Group A-3. Ahead of the convoy were three U-boat patrol lines; Vorwarts, of 18 boats, off the east of North America; Lohs, of 19 boats, south of Greenland, and Pfeil, 11 boats, moving west from bases in Occupied France. SC 100 passed through the Vorwarts patrol line without being detected, and these boats took no further part in the action, but on 18 September the convoy was found and reported by GS U-599, of Lohs. U-599 commenced shadowing, while other U-boats of the group joined; first GS U-755, which had sunk the USCG weather ship Muskeget the previous week, then GS U-259 and  GS U-569. These boats began their attack, but U-259 collided with a merchant ship and was forced to break off. Both boats were vigorously attacked by escort ships, but suffered no damage. Two more Lohs boats, GS U-373 and GS U-596 joined; the latter attacked and sank the freighter Empire Hartebeeste, but a claim by U-373 to have torpedoed a corvette was not substantiated.

At this point a massive storm blew up (described by U-boat reports as "a hurricane"), making further attempts impossible. Faced with this BdU called off the operation, but several boats remained in contact and on the third day GS U-617, of Pfeil made contact and torpedoed Athelsultan, the commodores ship. U-617 also sank the stragglers Tennessee and Roumanie, which had become separated in the storm. Meanwhile, SC 100 had been re-inforced by ships from nearby convoys, and from 20 EG, bringing the total number of warships to 15. On 24 September two more U-boats made contact; GS U-432 sank the freighter Penmar, but a claim by GS U-258 of two freighters sunk was mistaken. The next day, as the weather cleared, aircraft of RAF Coastal Command were able to give saturation cover, forcing all U-boats still in contact to break off contact. With this BdU dropped plans to re-engage with SC 100 and moved the U-boats present to other tasks. With no further attacks SC 100 arrived safely at Liverpool on 28 September.

Assessment
Despite the number of U-boats called to this action few were able to make contact, due to the storm. Those that did were driven off by the escorts; of the five ships sunk by enemy action only two were in convoy at the time. It has been suggested that the ships of Group A-3 were not fast enough to catch surfaced U-boats; but Donitz attributed the failure of the attack on the aggressive handling of the escorts as well as the appalling weather. The U-boats sank five scattered ships before losing contact on 25 September; another was lost in a collision. Twenty ships arrived safely.

SC 100 was one of three North Atlantic convoys attacked during September; in the same period the Allies sailed nineteen convoys comprising some 580 ships. Total losses were 19 ships and two escorts, (some 3% of ships involved); the cost to the U-Boat Arm was five boats lost, and another four damaged sufficiently to be returned to base.

U-boats
The convoy was attacked by both Wolfpack Lohs comprising 9 U-boats, and 8 U-boats from Wolfpack Pfeil, namely

Wolfpack Lohs

 * GS U-135 (1941)
 * GS U-176
 * GS U-259
 * GS U-373
 * GS U-410
 * GS U-432
 * GS U-569
 * GS U-599
 * GS U-755

Wolfpack Pfeil

 * GS U-216
 * GS U-221
 * GS U-258
 * GS U-356
 * GS U-595
 * GS U-607
 * GS U-615
 * GS U-617