SC 42 is one of the better-known convoys of World War II. Its story is told in many of the histories of the Battle of the Atlantic. SC were the code letters that the Admiralty assigned to convoys that were sent from Nova Scotia to the United Kingdom and 42 was the sequential number given to the convoy as it left port. SC 42 was therefore traveling on the most important trade route of the war during one of the most important times in the conflict, September 1941. It was a large convoy composed of sixty-four merchant ships with a combined total of 500,000 tons, many of which were old, slow bulk carriers carrying raw materials for Britain's factories, such as lumber, iron ore and phosphates. However, for such a large convoy it had a relatively small, if seasoned, escort force of one destroyer and three corvettes, all Royal Canadian Navy (RCN) vessels. There were also two other destroyers training in the North Atlantic at the same time which could conceivably be called upon if the convoy ran into trouble.

And run into trouble it did. As SC 42 had a top speed of only 7 knots, it was ideally suited for U-boat attacks. The importance of convoy speed had become well understood by the summer of 1941. U-boats of the Type VII class could only travel at 8 knots while submerged, so a convoy of this speed or lower could be hunted by German submarines which could remain hidden until the last possible moment. On September 9, 1941, as SC 42 was running very close to the east coast of Greenland, it crossed paths with a large U-boat wolfpack, codenamed Markgraf, at first composed of eight boats. On that evening, when the U-boats could operate on the ocean surface free from air attack and able to reach high speeds, Markgraf started to rip into SC 42’s flesh. Sometimes darting between the mostly helpless merchant ships, the U-boats sank seven vessels the first night.