On the night of 9 September 1941, Convoy SC-42 had sailed past the south coast of Greenland. Four Royal Canadian Navy (RCN) corvettes, HMCS Moose Jaw , HMCS Chambly , HMCS Kenogami , and HMCS Skeena , escorted the convoy. That night, a well-coordinated German submarine attack claimed seven merchant vessels and an eighth was torpedoed as the sun rose.
The attacks subsided during the day of 10 September, but, as dusk fell, the German submarines renewed their assault on Convoy SC-42. Captain Chummy Prentice of the RCN corvette HMCS Chambly anticipated that the enemy would attack the convoy from the south. Together with the corvette HMCS Moose Jaw , the Chambly moved to intercept the German submarines. Almost immediately, Prentice's ASDIC (a type of sonar that used sound to locate submerged submarines) team reported the location and depth of a U-boat. Prentice ordered the crew of the Chambly to execute a fast attack with five depth charges. Within minutes, the heavily damaged German submarine U-501 struggled to the surface.
The captain of the Moose Jaw , Freddie Grubb, ordered his crew to ram the damaged vessel, but the small corvette merely glanced off the submarine's hull. As the Moose Jaw pulled back, the Chambly drew alongside the stricken submarine, and Lieutenant Ted Simmons led a boarding party onto U-501. Simmon's goal was to seize the German code books and code machines. The German captain, however, had already opened the submarine's hatches, and U-501 quickly sank. The incident claimed the lives of 11 German sailors and a member of the Canadian boarding party.
Although U-501 was the first confirmed sinking of German submarine by a RCN corvette, the situation of Convoy SC-42 continued to be dire. The German U-boats continued their relentless attacks, and the convoy lost an additional eight ships the following night.