The U-boat had earlier torpedoed the 5,196 GRT steamer Aymeric,[4][5] the last British cargo ship in the Atlantic to be sunk that month, claiming the lives of 53 men.

[7] On 10 July 1943 Swale sailed Gibraltar to rendezvous with the small, fast Convoy Faith (one of the 'Winston Specials')[8] en route from Greenock in Scotland to Freetown, Sierra Leone.

[9] The convoy had comprised two troopships, the California and the Canadian Pacific liner Duchess of York, and the transport Port Fairy, (which was carrying ammunition), escorted by three warships.

At about 2000 hrs on 11 July while 300 miles (480 km) west of Vigo, the convoy was subjected to a devastating air attack by three Focke-Wulf Fw 200 Condor aircraft from Merignac airfield near Bordeaux.

By the time Swale arrived at 2235 hrs, both California and Duchess of York had been hit, set on fire, and abandoned, to be sunk later by torpedoes from their escorts.