Summary and Key Points: A nuclear-powered Nimitz-class aircraft carrier costs roughly $5,500,000,000 in today’s money. The Canadian diesel submarine that “sank” one in a NATO exercise was worth about $80,000,000, ran on batteries, and had been bought in the 1960s mostly for training. Canada’s three Oberon-class boats — HMCS Ojibwa, Onondaga and Okanagan — were upgraded through the 1980s with anechoic tiling and modernized systems, and their real advantage was simple: on battery power a diesel boat makes almost no noise at all. One of them was assigned to play the enemy against a carrier group centered on USS Dwight D. Eisenhower and screened by destroyers, cruisers, submarines, and carrier aircraft. It got inside all of it, simulated a torpedo launch, and the US Navy officer umpiring the exercise ruled the carrier destroyed.
How Canada Managed to ‘Sink’ A US Navy Aircraft Carrier in Mock Combat
The Canadian Royal Armed Forces maintains a modest navy compared to the United States. However, even with a significantly smaller budget and a smaller overall size, any navy with decent submarine capabilities can pose a credible threat.
However, there have been multiple occasions in which Canadian or other NATO submarines have successfully managed to sneak past entire carrier strike groups and simulate a successful attack against an American supercarrier.
The Canadian Navy vs the USS Eisenhower
The Canadian Navy, though modest in size and budget compared to its American counterpart, had long maintained a reputation for professionalism and tactical skill. Its Oberon-class submarines (HMCS Ojibwa, Onondaga, and Okanagan) were originally acquired in the 1960s primarily for training purposes.
However, by the 1980s, these submarines had undergone significant upgrades that enhanced their combat capabilities. Their hulls were fitted with anechoic tiles to reduce sonar detection, and their systems were modernized to improve underwater endurance and stealth. Though not nuclear-powered, these submarines had a distinct advantage: they could operate almost silently on battery power, making them exceptionally difficult to detect.
USS Dwight D. Eisenhower. Image Credit: Creative Commons.
USS Dwight D. Eisenhower. Image Credit: U.S. Navy.
In 1981, NATO and other Western allies held Ocean Venture, a joint naval exercise in the Atlantic Ocean. During the exercise, one of these Canadian submarines (details are so scarce on this exercise that we don’t even know which one it was) was assigned the role of an enemy vessel attempting to infiltrate the carrier group’s defenses.
The carrier group itself was a formidable formation, centered around a U.S. Navy supercarrier, the USS Eisenhower (CVN-69), and protected by a screen of destroyers, cruisers, and submarines, along with air support from carrier-based aircraft. The group’s mission was to detect and neutralize any underwater threats before they could reach the carrier.
When an Antiquated Canadian Diesel Submarine Took Out an American Super Aircraft Carrier
The Canadian submarine’s mission was simple in concept but extraordinarily difficult in execution: approach the carrier undetected and simulate a torpedo attack.
What followed was a masterclass in stealth and tactical maneuvering. Using the natural acoustic conditions of the ocean and its own quiet propulsion system, the submarine slipped past the outer defenses of the carrier group. It evaded sonar-equipped destroyers and surveillance aircraft, exploiting gaps in coverage and limitations imposed by the exercise’s rules of engagement.
At the critical moment, the submarine simulated a torpedo launch. The exercise umpire, a U.S. Navy officer tasked with adjudicating the scenario, evaluated the situation and declared the carrier “sunk.”
In today’s dollars, the Nimitz-Class aircraft carrier would cost around $5.5 billion, while Canada’s sub comes in at a cheap $80 million.
The Canadian submarine had achieved its objective without being detected, effectively demonstrating that even the most powerful warships in the world were vulnerable to stealthy underwater threats.
Canada Victoria-Class Submarine. Image Credit: Creative Commons.
The incident raised several uncomfortable questions.
How could a relatively underfunded navy with decades-old technology defeat a modern carrier group?
Was the U.S. Navy’s anti-submarine warfare doctrine flawed?
Were diesel-electric submarines being underestimated in contemporary naval strategy? These questions prompted a reevaluation of ASW tactics and capabilities across NATO.
Never Underestimate Submarines
The success of the Canadian submarine can be attributed to several key factors. First and foremost was the professionalism and training of the Canadian submariners. Their ability to exploit weaknesses in the carrier group’s defense was a testament to their skill and discipline. Second was the inherent stealth of the Oberon-class submarine.
Operating on battery power, it was nearly undetectable to passive sonar systems, especially under the exercise’s constraints, which limited the use of active sonar to simulate real-world conditions. Third, the exercise itself imposed rules that may have skewed outcomes.
Ships were not operating at full speed, and sonar use was restricted, creating opportunities for submarines to succeed in ways that might be more difficult in actual combat.
Components of the Dwight D. Eisenhower Strike Group (IKECSG) and the fast combat support ship USNS Supply (T-AOE 6) transit the Strait of Hormuz, Dec 14, 2023. As part of the Dwight D. Eisenhower Carrier Strike Group (IKECSG), the Philippine Sea is deployed to the U.S. 5th Fleet area of operations to help ensure maritime security and stability in the Middle East region. (U.S. Navy photo by Mass Communication Specialist 2nd Class Keith Nowak)
Perhaps most importantly, the incident highlighted a broader strategic oversight: the underestimation of diesel-electric submarines.
At the time, the U.S. Navy was heavily invested in nuclear-powered submarines and may have viewed conventional boats as outdated. The exercise demonstrated that diesel-electric submarines, particularly when operated by skilled crews, remained a potent threat in modern naval warfare.
This Has Happened Before
The Canadian success in Ocean Venture was not an isolated incident. Similar outcomes occurred in other exercises involving allied diesel submarines. There have been around eight instances of submarines, mostly diesel-powered, successfully “sinking” American carriers in exercises from 1972 to 2005.
Dutch and Australian submarines also achieved simulated kills against U.S. carriers in subsequent war games. These events underscored the vulnerability of even the most advanced naval formations to stealthy underwater threats, prompting a renewed focus on ASW training and technology.
Since the Ocean Venture, submarine technology has undergone significant improvements. Non-nuclear submarines equipped with air-independent propulsion (AIP) can travel quietly, significantly enhancing their stealth characteristics.
Gotland-Class. Image Credit: Creative Commons.
Gotland-class submarine. Image Credit: Creative Commons.
This is to say nothing of nuclear attack submarines, which have sunk multiple carriers during exercises.
Anti-submarine warfare has also advanced with the development of better radars, sonars, and more sophisticated means of protection; however, none of these are foolproof.
While a lot of noise is made about hypersonic missiles, the real threat to carriers has been, and likely always will be, submarines.
About the Author: Isaac Seitz
Isaac Seitz, a Defense Columnist, graduated from Patrick Henry College’s Strategic Intelligence and National Security program. He has also studied Russian at Middlebury Language Schools and has worked as an intelligence Analyst in the private sector.