Although not crippling to the Canadian war effort, given the country's rail network to the east coast ports, but possibly more destructive to the morale of the Canadian public, was the Battle of the St. Lawrence, when U-boats began to venture upriver and attack domestic coastal shipping along Canada's east coast in the St. Lawrence River and Gulf of St. Lawrence from early 1942 through to the end of the shipping season in late 1944. From a German perspective this area contained most of the military assets in North America that could realistically be targeted for attack, and therefore the St. Lawrence was the only zone that saw consistent warfare—albeit on a limited scale—in North America during World War II. Residents along the Gaspé coast and the St. Lawrence River and Gulf of St. Lawrence were startled at the sight of maritime warfare off their shores, with ships on fire and explosions rattling their communities, while bodies and debris floated ashore. The number of military losses is not known, although loose estimates can be made based on the number of surface units and submarines sunk.