Canada and Antisubmarine Warfare during the Cold War

During the Cold War, the Canadian Navy played a crucial role in antisubmarine warfare (ASW), working closely with its allies to patrol and monitor the North Atlantic and Pacific Oceans for Soviet submarine activity. Canada invested in new technology and continually modernized its fleet of ships and aircraft to better detect and counter Soviet submarines. It also operated strategic warning systems with its allies, particularly the United States. By the end of the Cold War, Canada had developed a very high reputation in the field.

During the Cold War, the Canadian Navy played a crucial role in antisubmarine warfare (ASW), working closely with its allies to patrol and monitor the North Atlantic and Pacific Oceans for Soviet submarine activity. Canada invested in new technology and continually modernized its fleet of ships and aircraft to better detect and counter Soviet submarines. It also operated strategic warning systems with its allies, particularly the United States. By the end of the Cold War, Canada had developed a very high reputation in the field.

HMCS Bonaventure


During the Cold War (from about 1946 to 1991), much of the world was divided into two ideological camps. The capitalist “West” was led by the United States while the communist “East” was dominated by the Soviet Union. Canada was allied with other Western countries, including membership in the North Atlantic Treaty Organization (NATO) and the North American Aerospace Defence Command (NORAD). The Cold War never developed into open, “hot” warfare. But the threat was real and the stakes high. The threat of enemy submarines to Canada and its allies was even higher than during the Second World War (see U-Boat Operations).

The Second World War ended with ASW still in its infancy. German U-boats were primarily surface vessels that could submerge only for short periods; sonar ranges were limited to a few thousand metres, and initial contact largely was visual or by radar on the surface. This soon changed in what historians have labelled “the postwar naval revolution,” which included the development of nuclear-powered submarines. Compared to conventional submarines, nuclear vessels were faster and could operate underwater for longer periods and at a much greater range. During the Cold War, Western and Soviet submarines were also equipped with long-range torpedoes and anti-ship missiles, and eventually intercontinental ballistic missiles which now threatened the cities of continental North America. At the same time, the Western allies, particularly the United States Navy (USN), gained a better understanding of oceanographic conditions, which in turn guided the development of long-range sensors. They also developed weapon systems with higher accuracy and longer range, and purpose-built ships and aircraft to deliver them.

SSBN de la classe Hotel 1972

Antisubmarine Warfare, 1946–62

By 1947, Western intelligence had identified the Soviet Union as the only foreseeable naval threat. The Soviets had a negligible ocean-going surface fleet but were already adapting captured German submarine technology to produce large numbers of advanced conventional attack submarines.

In 1949, NATO was established to counter the rising Soviet threat. Around the same time, the Royal Canadian Navy (RCN) began work on the first major class of warship to be designed and built in Canada: the St Laurent-class “destroyer escorts” were purpose-built for antisubmarine warfare, incorporated the latest ASW sensors and weapons and could remain at sea for extended periods without need for refuelling. They quickly became known as the “Cadillac” destroyers. The lead ship, however, was not launched until 1955. In the interim, 21 Second World War-vintage River-class frigates were taken out of reserve, upgraded with similar equipment, and designated the Prestonian-class “ocean escorts.”

In the 1950s, the USN established the Sound Surveillance System (SOSUS), a network of passive sonar devices laid on the ocean bottom capable of “listening” for submarines at ranges of hundreds of kilometres. The network was set up as a web of stations up and down the east and west coasts of North America. The RCN operated one at Shelburne, Nova Scotia, and helped run two others, at Argentia, Newfoundland, and Whidbey Island, Washington.

The Royal Canadian Air Force (RCAF) played an important role in ASW as well. Beginning in 1951, Second World War-era Lancaster bombers were converted for ASW. In 1955, the RCAF purchased 33 medium-range Lockheed P2V Neptune aircraft, while developing their own long-range maritime patrol aircraft, the Canadair CL-28 (later CP-107) Argus. The first Argus entered service in 1958, and a total of 33 were produced.


Together with SOSUS, these ships and aircraft were the pinnacle of ASW capability in the Western alliance — and hence the world. The RCN and RCAF also set up a joint “Maritime Command” in 1957 to better coordinate ASW during the early Cold War. (Maritime Command became the model for unification of the Canadian Armed Forces a decade later.)

This was the state of Canadian ASW forces at the time of the Cuban Missile Crisis in October 1962, when the US discovered that Soviet ballistic missiles were being installed on the island. Maritime Command joined the United States’ embargo of Cuba, deploying ships and aircraft to their war stations to patrol the North Atlantic. The resolution of the crisis was the withdrawal of Soviet missiles from Cuba — and of their ships and submarines from the quarantine zone.

Cuban Missile Crisis

Antisubmarine Warfare, 1962–91

The Cuban Missile Crisis, however, had underscored the limitations of Canadian ASW. The Soviets had sent conventional submarines to Cuba. The outcome could have been very different if they had sent nuclear-powered vessels, which were faster and could dive much deeper. Canadian warships weren’t fast enough and their ship-mounted weapons had too short a range. These shortcomings had become obvious during exercises with USN submarines in the mid-1950s, so Canada had already started to address them by the time of the Cuban Missile Crisis. In the remaining decades of the Cold War, the navy would focus on improving its ASW capacity.

The height of the peacetime RCN

The most important realization was that aircraft had the speed and versatility to attack nuclear submarines, and that ship-based aircraft could respond faster than shore-based ones. In 1959, the RCN acquired the CS2F-1 Grumman Tracker to operate from the aircraft carrier HMCS Bonaventure. Early in 1962, the Bonaventure was also outfitted with Sikorsky HO4S ASW helicopters. This made her one of the earliest allied fleet carriers to be focussed on the ASW mission. In 1964, the HO4Ss were replaced with the very capable Sikorsky CHSS-2 (later CH-124) Sea King helicopters. HMCS Bonaventure was widely expected to be a fundamental part of Canadian ASW operations for decades. This came to a sudden end in 1970, however, when the carrier was taken out of service as a cost-saving measure following unification of the armed forces.

With the decommissioning of the Bonaventure, the Trackers were transferred ashore. Yet the navy had another platform for the Sea King helicopters. The RCN began investigating the operation of ASW helicopters from smaller escorts in the mid-1950s. By 1959, they had proven the value of a Canadian-designed “Beartrap” haul-down system for use in the heavy seas of the northern oceans. Between 1962 and 1966, all seven of the original St Laurents were converted to “helicopter-carrying destroyers” (DDH), each fitted with a hangar and landing deck for a Sea King helicopter.

The St Laurents were also fitted with another pioneering technology, variable depth sonar (VDS), which allowed ships to detect submarines at a greater range. VDS became a standard feature of all Canadian warships until overtaken by later innovations in the 1980s. Importantly, the combination of VDS with helicopter-carrying destroyers quickly proved powerful, and soon would be adopted by most other Western (and eventually Soviet) navies.

These innovations were just a sub-set (albeit a large one) of Canadian naval research, as the RCN tried to remain a general-purpose fleet. However, unification of the Canadian Armed Forces in 1968 coincided with significant growth in government social programs, resulting in drastic cuts to the defence budget. Consequently, ASW became Canada’s primary maritime contribution to NATO.

Meanwhile, Soviet naval capabilities were improving as well. New classes of nuclear-powered attack and ballistic missile-firing submarines were entering service, along with a growing fleet of surface ships and long-range bombers designed to seek out and attack allied convoys. In addition to submarine torpedo attack, allied warships now had to contend with the “air” threat from missiles fired by Soviet ships, aircraft, and soon also submarines. Even VDS couldn’t detect the new threats at a safe distance.

The most effective immediate counter response was the air force’s replacement of the Argus in the early-1980s with the CP-140 Aurora. The answer for naval vessels would prove to be the towed array sonar (TASS): a mobile version of the SOSUS-type passive array, adjustable for towing at varying lengths and depths from a ship or submarine. The Canadian navy’s contribution to the system was the adoption of a powerful onboard signal processing computer. CANTASS had detection ranges in the hundreds of kilometres and was fitted operationally in the late-1980s to the DDHs Fraser, Annapolis and Nipigon. CANTASS was the primary sensor for the Halifax-class frigates that entered service in the early-1990s, just after the Cold War ended.

No discussion of Cold War ASW is complete without acknowledging that, in the age of highly manoeuvrable, deep-diving and long-submerging vessels, the best antisubmarine weapon is another submarine. The Canadian Navy made several attempts to create an ASW submarine fleet during the Cold War but was unsuccessful. In the late 1950s, the navy considered buying USN Thresher-class nuclear-powered or Barbel-class conventional attack submarines but decided that it was too costly. Instead, it commissioned three conventional British Oberon-class submarines, but for training purposes only. These were upgraded in the early 1980s with Mk 48 torpedoes and an improved fire control system and enjoyed some success on operational patrols off the east coast. In 1987, the Progressive Conservative government under Brian Mulroney tabled the 1987 Defence White Paper, an ambitious defence policy proposal that included the acquisition of 10–12 nuclear-powered submarines. The Cold War ended soon after, however, and the idea was abandoned.