Halifax grew in importance, particularly as Germany introduced use of submarines for the first time to a large-scale conflict, requiring the Royal Canadian Navy and the Royal Navy to institute the use of convoys for protecting ships. Halifax's protected harbour allowed ships to load and form up into convoy formations under protection due to torpedo nets strung across the harbour entrance. The ICR swelled in its ranks of employees and equipment as it struggled to carry the burden of military supplies from central Canada to the Atlantic coast. After 1915, the busy wartime railway officially operated under the name Canadian Government Railways but continued to be widely known as the Intercolonial. An equally important connection was the line from Cape Breton where the largest private employer in Canada, the Dominion Steel and Coal Company (through its predecessors) produced vast quantities of steel and coal for the war effort, much of which was carried by the ICR westward to other industrial centres, before returning via Halifax for shipment overseas.