The Battle of the Atlantic, the longest single engagement of the Second World War, resulted in the coming-of-age of the Royal Canadian Navy. By 1945, the Canadian Navy had transformed from a small force of a mere 3,500 personnel and 13 vessels, into the third-largest naval power in the world, all in order to face the threat of the infamous German U-boats. As these submarines threatened to weaken the Allied war effort by targeting shipping vessels, the Canadian Navy was put to work protecting convoys across the Atlantic and hunting for submarines just off the coast of Atlantic Canada. War at Sea describes the history of this engagement through a detailed catalogue of the technology, weapons, and ships, including frigates, corvettes, and fairmiles, that the Canadian Navy depended on. Author Ken Smith tells the stories of the danger and action faced by the RCN, such as the torpedoed HMCS Levis, the first Canadian warship lost to enemy fire. Smith further recognizes the contribution of Atlantic Canadians, who worked in shipyards targeted by submarine attack, and who alerted police to German spies in their midst. The history of these events is supplemented by first-hand accounts from the veterans who survived these encounters and 25 historical photos.