The Battle of the Gulf of St. Lawrence, which saw German U-boats penetrate the Cabot Strait and the Strait of Belle Isle to sink 23 ships between 1942 and 1944, marked the only time since the War of 1812 that enemy warships inflicted death within Canada's inland waters. The battle advanced to within 300 kilometres of Québec City. A war that pervaded people's lives but was still somehow remote, had become immediate, threatening, and very real. This site outlines the story of this battle.

In 1944 German U-boats returned to the Gulf of St. Lawrence, which had been re-opened to trans-Atlantic vessels, intent on repeating their successes of 1942. By this time the Royal Canadian Navy was more adept at anti-submarine warfare, and its convoy procedures were much improved. Maritime air patrols were more proficient too. The U-boats returned with a potentially deadly advantage, however: the newly invented schnorkel mast.

This report discusses the measures taken by the Army to safeguard the civil population and vital installations in the Lower St. Lawrence region as a result of the incursion of German submarines into the Gulf and River in 1942. After Japanese forces struck at Pearl Harbour, the whole
perspective of the war was changed and the Allied powers had to redistribute their naval resources to cover the new areas in the Pacific and Indian Oceans. The German enemy's response to this new situation was to mount more agressive U-boat attacks from the Atlantic and heading westward.

During the Battle of the St. Lawrence, the last loss of the 1942 season was the largest, and perhaps the most tragic. It was the Sydney to Port aux Basques ferry Caribou, which was sunk by a German U-boat in Cabot Strait during the early morning hours of October 14, 1942. More than any other event, the loss of the Caribou revealed to all Canadians our vulnerability to seaward attack and brought home the fact that the war wasn't just a European show.

In January 1943 the Canadian Mid-Atlantic Escort Force was withdrawn for re-equipping and training following the disastrous German submarine campaign in the Gulf of St. Lawrence. The weakness shown by the Canadian Navy forced the closure of the St. Lawrence to Canadian shipping and a re-examination of the Navy’s role.

Despite early growing pains, the Royal Canadian Navy grew into a formidable anti-submarine force. The R.C.N. sank 28 enemy submarines and escorted Allied shipping across the Atlantic and along the northeastern seaboard of North America.

Faced with a rising toll on lives and shipping, the Canadian government closed the St. Lawrence to all trans-Atlantic shipping on September 9, 1942, and limited coastal convoys to essential levels. This site gives an account of the battle of the St. Lawrence during the month of September 1942.

The HMC Prince David, Prince Henry and Prince Robert ships were built at Birkenhead in the United Kingdom by Cammell Laird for the Canadian National Steamships Company. By the 1930s they sat idly much of the time because of the decade's decline in trade. When war broke out in September of 1939, the Naval Service lost no time in making arrangements for the conversion of the Princes, adding anti-submarine weaponry for armed merchant cruiser operations.

The Canadian solution to the German submarine threat were corvettes – small ships which were very manoeuvrable and equipped with ASDIC (Sonar). The small size of the Canadian navy was not able to meet the need for a vast expansion, and new ships were often ill-equipped with untrained crews and inexperienced officers. The escort force suffered serious losses calling into question the Navy's ability to carry out its job.