Key Points and Summary – In a 2005 war game, a $100 million Swedish Gotland-class submarine repeatedly “sank” the $6 billion USS Ronald Reagan aircraft carrier.
-Its revolutionary Air-Independent Propulsion (AIP) system allowed it to operate with extreme stealth, remaining submerged for weeks and moving with near-total silence.
Ford-Class. Image Credit: Creative Commons
-It effortlessly slipped past the carrier’s formidable defenses, highlighting the vulnerability of even the most powerful warships to modern, quiet, conventional submarines.
-The shocking result was a wake-up call for the U.S. Navy, proving that stealth, not size, is the ultimate advantage in modern underwater warfare, a lesson now being adopted by nations like China.
Yes, an Aircraft Carrier Was Sunk by a Swedish Gotland-Class AIP Submarine
Even in the era of the Ford-class, at least for the moment, nothing projects American might quite like a Nimitz-class aircraft carrier.
It is a symbol of overwhelming force, a floating city and sovereign U.S. territory that carries an air wing more powerful than what most entire nations possess.
Surrounded by a protective screen of cruisers, destroyers, and hunter-killer submarines, this $6 billion steel behemoth is designed to be the untouchable queen of the seas, the centerpiece of a naval strategy that has dominated the world’s oceans for over half a century.
The prevailing wisdom has always been that sinking one would be a near-impossible feat, a Pyrrhic victory at best for any adversary foolish enough to try.
Then, in 2005, during a series of war games in the Pacific, this entire assumption of invincibility was shattered.
Amphibious assault ship USS Makin Island (LHD 8) and aircraft carrier USS Nimitz (CVN 68) perform expeditionary strike force (ESF) operations, Feb. 15, 2023 in the South China Sea. Nimitz Carrier Strike Group (NIMCSG) and amphibious assault ship USS Makin Island (LHD 8) with embarked 13th Marine Expeditionary Unit are conducting joint ESF operations, representing unique high-end war fighting capabilities, maritime superiority, and power projection, demonstrating the U.S. commitment to our allies and partners in the Indo-Pacific region. (U.S. Navy photo by Mass Communication Specialist 3rd Class Kendra Helmbrecht)
The mighty USS Ronald Reagan, one of America’s newest and most advanced supercarriers, was repeatedly “sunk.”
There was no massive peer-competitor fleet, no barrage of hypersonic missiles, no nuclear exchange.
The giant was brought down by a lone assassin: a tiny, diesel-electric submarine from Sweden, the HSwMS Gotland. This small hunter, built for a cost of around $100 million, slipped through the most sophisticated anti-submarine defenses on the planet, lined up the carrier in its periscope, and simulated firing torpedo after torpedo into its hull.
And it did this repeatedly, without ever being detected.
The event sent a profound shockwave through the halls of the Pentagon. It was more than just an embarrassing loss in a training exercise; it was a terrifying validation of a threat that naval strategists had been quietly fearing for years.
The story of how this quiet hunter humbled a goliath is not just a fascinating piece of modern naval history.
(Left to right) Australian ANZAC Class frigate HMAS Stuart (FFH 153) and USS Jack H. Lucas (DDG 125) wait off the coast of the Pacific Missile Range Facility in Kauai, Hawaii, as they prepare for Flight Test Aegis Weapon System-32 (FTM-32), held March 28, 2024.
It is a stark and vital lesson about the nature of underwater warfare, a demonstration of a revolutionary technology that has since spread across the globe, and a brutal reminder that in the silent world beneath the waves, size and price are no guarantee of survival.
The Ghost in the Machine: What Makes the Gotland Special?
To understand how the Gotland achieved the impossible, you have to understand the fundamental weakness of every submarine ever built before it, with the exception of nuclear-powered ones: the need for air. For decades, conventional submarines ran on diesel engines, which, like any internal combustion engine, need oxygen to burn fuel.
This meant they could only run their main engines on the surface. Underwater, they relied on massive banks of batteries. When the batteries ran low after a day or two of slow, submerged cruising, the submarine had to come up to periscope depth and raise a snorkel—a breathing tube—to run its diesel engines and recharge.
This act of snorkeling is the moment of greatest vulnerability. A submarine with its snorkel up is noisy, its diesel engines creating a distinct acoustic signature that can be picked up by listening devices. The snorkel mast itself can be detected by radar. For an adversary’s anti-submarine warfare (ASW) forces, a snorkeling sub is a wounded animal coming up for air, and it is the moment they are most likely to find and kill it.
The Swedish engineers at Kockums shipyard, designing a submarine to defend their nation’s complex and shallow coastline in the Baltic Sea, knew they had to solve this problem. Their solution was a revolutionary technology called Air-Independent Propulsion, or AIP.
The aircraft carrier USS George Washington (CVN 73) prepares to conduct a refueling at sea with the guided missile cruiser USS Monterey (CG 61) as the two ships operate in the Caribbean Sea on April 20, 2006. The George Washington Carrier Strike group is participating in Partnership of the Americas, a maritime training and readiness deployment of U.S. Naval Forces along with navies of Caribbean and Latin American countries for enhanced maritime security.
(DoD photo by Petty Officer 3rd Class Michael D. Blackwell II, U.S. Navy. (Released))
The Gotland-class was the first in the world to be designed from the ground up with this system, and it is the secret to its lethality.
At the heart of its AIP system is the Stirling engine. Unlike a diesel engine, which uses internal combustion, the Stirling engine uses an external heat source to expand and contract a gas (in this case, helium) in a closed loop, driving pistons.
The genius of the Swedish design was to fuel this process by mixing liquid oxygen, carried in cryogenic tanks, with diesel fuel in a pressurized combustion chamber. Because the engine is not powered by a series of controlled explosions, it is astonishingly quiet and virtually vibration-free.
When running on its AIP system, the Gotland does not need to snorkel. It can cruise silently underwater for weeks at a time, not just days. A nuclear submarine, for all its unlimited range, must constantly run cooling pumps for its reactor, creating a persistent, low-level noise that can be tracked by sensitive sonar.
But a submarine on AIP, moving slowly, can become one with the background hum of the ocean. It is, for all intents and purposes, a ghost. It doesn’t need to come up for air, and it makes almost no sound. It can lie in wait, motionless on the seabed, or creep along at a few knots, becoming an invisible predator. This is the capability that the U.S. Navy’s carrier strike group was simply not prepared for.
The Kill Shot and the Humbling Aftermath
The 2005 exercise was designed to test the defenses of a full Carrier Strike Group—the USS Ronald Reagan and its flotilla of Aegis-equipped destroyers and cruisers, its ASW helicopters, and its own attendant nuclear-powered hunter-killer submarines. This multi-layered defense creates a “bubble” of sensors stretching for hundreds of miles, intended to detect any threat long before it can get close to the carrier.
241204-N-VW723-2064 PACIFIC OCEAN (Dec. 4, 2024) The Los Angeles-class fast-attack submarine USS Greeneville (SSN 772) transits the Pacific Ocean while supporting a distinguished visitor embark, Dec. 4, 2024. Greeneville is one of four Los Angeles-class fast-attack submarines assigned to Commander, Submarine Squadron 11. These submarines are capable of supporting various missions, including: anti-submarine warfare; anti-ship warfare; strike warfare; and intelligence, surveillance, and reconnaissance. (U.S. Navy photo by Mass Communication Specialist 1st Class Keenan Daniels)
The Gotland was the opposition force, the “red team.” Its mission was simple: penetrate the bubble and sink the carrier. Over the course of the exercise, the Swedish submarine and its highly trained crew did just that, with chilling efficiency. Leveraging the extreme quietness of its AIP system, the Gotland slipped past the outer screens of destroyers. It evaded the sonar nets of the helicopters and the prowling American submarines. It got inside the defensive perimeter, deep into the supposedly sterile water where no threat should have been able to exist.
Once inside, it was a turkey shoot. The Gotland’s captain had the freedom to maneuver at will, lining up perfect torpedo shots on the massive, 100,000-ton carrier. To prove its kills, the crew followed standard exercise procedure: they took photographs through the periscope. The images they captured were stunning—the towering gray hull of the Ronald Reagan, completely filling the viewfinder, blissfully unaware that it was already “dead.”
After each simulated attack, the Gotland would simply melt away back into the depths, its silence its greatest shield. By the end of the war games, the Swedish sub had racked up multiple kills on the carrier and suffered no losses. It was never conclusively detected.
The results were so shocking, so utterly one-sided, that they served as a brutal wake-up call for the U.S. Navy. This wasn’t a failure of crew or tactics; it was a failure of technology to account for a new and lethal threat. The Navy’s response was swift and telling. They didn’t just study the results of the exercise; they leased the Gotland itself.
For two years, from 2005 to 2007, a Swedish submarine and its crew were based in San Diego, where they were used as a dedicated sparring partner for the U.S. fleet. The Americans needed to learn how to fight this new kind of ghost, and the only way to do it was to train against the real thing. This unprecedented move was the clearest possible admission that the Gotland represented a paradigm shift in underwater warfare.
A Proliferating Threat in an Age of Great Power Competition
The humbling of the Reagan would be a concerning historical footnote if AIP technology had remained a niche Swedish specialty. But it hasn’t. In the two decades since that exercise, Air-Independent Propulsion has become a must-have feature for any nation seeking a modern and credible conventional submarine force. Germany, France, Japan, South Korea, and others have all developed their own AIP systems.
Most alarmingly for the Pentagon, China has embraced this technology with a vengeance. The People’s Liberation Army Navy has been mass-producing its Yuan-class submarines, which are equipped with their own Stirling-based AIP systems. These boats are quiet, capable, and being built in large numbers. This is not a coincidence. It is a core component of China’s anti-access/area-denial (A2/AD) strategy, which is designed with one primary goal in mind: to make it too dangerous for an American aircraft carrier to operate anywhere near Chinese territory, especially in a conflict over Taiwan.
Kilo-Class Submarine. Image Credit: Creative Commons.
China has watched and learned from the Gotland’s success. They understand that they don’t need a fleet of supercarriers to challenge the U.S. Navy. Instead, they are building a layered defense, combining their infamous “carrier-killer” anti-ship ballistic missiles with a growing fleet of these ultra-quiet AIP submarines. The strategy is clear: use the ballistic missiles to force U.S. carriers to operate from extreme ranges, and use the AIP submarines as silent assassins to patrol the critical straits and coastal waters, waiting to ambush any American warship that dares to come close.
This creates a terrifying dilemma. The Gotland proved that even one of these submarines, if it gets through, can neutralize America’s most powerful conventional weapon. What happens when an entire fleet of them is lurking in the waters of the Taiwan Strait? It fundamentally changes the risk calculation for any American president considering intervention.
The 2005 war game was a glimpse into the future of naval conflict. It was a clear demonstration that the age of the unchallenged supercarrier is over. These floating fortresses are no longer unsinkable.
In the silent, three-dimensional chess game of modern submarine warfare, a small, quiet, and relatively inexpensive predator can still checkmate a king. The legacy of the HSwMS Gotland is the uncomfortable but essential knowledge that the deadliest threats are often the ones you cannot hear coming.
About the Author: Harry J. Kazianis
Harry J. Kazianis (@Grecianformula) is Editor-In-Chief and President of National Security Journal. He was the former Senior Director of National Security Affairs at the Center for the National Interest (CFTNI), a foreign policy think tank founded by Richard Nixon based in Washington, DC. Harry has over a decade of experience in think tanks and national security publishing. His ideas have been published in the NY Times, The Washington Post, The Wall Street Journal, CNN, and many other outlets worldwide. He has held positions at CSIS, the Heritage Foundation, the University of Nottingham, and several other institutions related to national security research and studies. He is the former Executive Editor of the National Interest and the Diplomat. He holds a Master’s degree focusing on international affairs from Harvard University.
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