From the start of the war in 1939 until VE Day, several of Canada's Atlantic coast ports became important to the resupply effort for the United Kingdom and later for the Allied land offensive on the Western Front. Halifax and Sydney, Nova Scotia, became the primary convoy assembly ports, with Halifax being assigned the fast or priority convoys (largely troops and essential material) with the more modern merchant ships, while Sydney was given slow convoys which conveyed bulkier material on older and more vulnerable merchant ships. Both ports were heavily fortified with shore radar emplacements, searchlight batteries, and extensive coastal artillery stations all manned by RCN and Canadian Army regular and reserve personnel. Military intelligence agents enforced strict blackouts throughout the areas and anti-torpedo nets were in place at the harbor entrances, making a direct attack on those facilities unfeasible because it was impossible for Germany to provide air support. Even though no landings of German personnel took place near these ports, there were frequent attacks by U-boats on convoys departing for Europe once these had reached the mouth of the St. Lawrence. Less extensively used, but no less important, was the port of Saint John which also saw matériel funneled through the port, largely after the United States entered the war in December 1941. The port's location within the protected waters of the Bay of Fundy made it a difficult target for attack. The Canadian Pacific Railway mainline from central Canada (which crossed the state of Maine) could be used to transport in aid of the war effort.