SC 48 was an east-bound convoy of 52 ships, carrying war materials and sailed from Sydney, Cape Breton on 5 October 1941 bound for Liverpool.

At this point in time SC 48 was in some disarray; 11 of its ships, including Castalia, were straggling following heavy weather on the night of 9/10 October.

On 14 October SC 48's escort comprised just four corvettes; Wetaskiwin (as Acting SOE), Baddeck, Gladiolus and Mimosa.

On 15 October Enigma was re-acquired and Western Approaches Command realized a major attack was building; a number of escorts from nearby convoys were diverted to reinforce SC 48.

During the day U-558 joined, having encountered the ship Vancouver Island sailing independently ; she was sunk with the loss of all 73 crew and 32 passengers.

Gladiolus then detached to pick up survivors, but never rejoined the convoy; she was lost with all hands, reportedly sunk by U-568 on the 17th, but more probably much earlier.

Though he had seniority, Thebaud had little experience in escort work, and a number of mistakes were made allowing the U-boats to mount a successful attack that night.

The RCN group departed at this point, being low on fuel; also DesRon 13 left to follow Kearny to Iceland.

On the night of 17/18 October the pack tried again; all attacks were repelled but U-101 fired on Broadwater, causing her mortal damage; she remained afloat for another 12 hours, but had to be abandoned and sunk.

Led by Commodore Sanders in Castalia and with just two corvettes as escort this group was able to make the crossing without interference, arriving in Britain 10 days after the main body.

This, and other cases, led to the practice of leaving the escort group commander of the convoy in charge of its defence, regardless of seniority; a major break with tradition.

The attack on Kearny and the loss of American lives was seen as an affront to the United States, and was another step out of her isolation in World War II.