In 2005, the United States Navy conducted a series of naval war games to test how well its carrier strike groups could defend against submarines, an initiative to assess the range, resolution, and effectiveness of its sonar detection and anti-submarine weapons.
One of the most memorable exercises involved the Swedish diesel-electric submarine Gotland sinking a massive U.S. carrier in a simulated exercise.
(Feb. 15, 2023) U.S. Navy aircraft carrier USS Nimitz (CVN 68) flies the battle ensign during expeditionary strike force operations with the Nimitz Carrier Strike Group including the Arleigh Burke-class guided-missile destroyer USS Decatur (DDG 73). Nimitz Carrier Strike Group (NIMCSG) and Makin Island Amphibious Ready Group (MKI ARG) with embarked 13th Marine Expeditionary Unit (MEU) are conducting combined ESF operations, demonstrating unique high-end war fighting capability, maritime superiority, power projection and readiness. Operations include integrated training designed to advance interoperability between the two groups while simultaneously demonstrating the U.S. commitment to our alliances and partnerships in the Indo-Pacific region. (U.S. Navy photo by Mass Communication Specialist 2nd Class David Negron)
Using its quiet diesel engine, the Swedish boat managed to elude detection and destroy the U.S. Navy’s USS Ronald Reagan.
While no ship was actually damaged, the event had a large impact on U.S. naval thinking and sharpened focus upon the growing effectiveness of quiet, non-nuclear submarines.
At the time, the USS Ronald Reagan was one of the newest and most advanced nuclear-powered aircraft carriers in the world.
By traveling in a carrier strike group, the Ronald Reagan was protected by guided-missile cruisers, destroyers, aircraft, and nuclear attack submarines.
Cold War Defenses
These defenses were primarily designed during the Cold War, when the main undersea threat came from large, fast, nuclear-powered Soviet submarines.
Inexpensive, older diesel-electric submarines such as the Gotland were not regarded as a threat comparable to the perceived Soviet threat.
The Gotland was able to elude helicopter, sonar, and surface warship sensors to find the “quiet space” and exploit the “gaps” in submarine detection.
The Gotland was equipped with air-independent propulsion (AIP), allowing it to operate underwater for extended periods without surfacing.
Gotland-Class Submarines. Image Credit: Creative Commons.
When running on battery power, the submarine was exceptionally quiet—often quieter than the ocean’s ambient noise.
This mode made detection by traditional sonar systems extremely difficult, particularly in shallow or coastal waters.
During the war games, the Gotland was tasked with playing the role of an enemy submarine attempting to attack a U.S. carrier strike group.
In one widely cited exercise, the submarine successfully evaded the escorting ships and aircraft, maneuvered into firing position, and executed a simulated torpedo attack against the carrier.
In naval exercises, such an outcome is often referred to as a “kill,” meaning that, under real combat conditions, the targeted ship would likely have been disabled or sunk.
Reports of this simulated attack led to the dramatic claim that Gotland had “sunk” the USS Ronald Reagan.
Small Submarine Sinks U.S. Navy Aircraft Carrier in Drill
A relatively small, conventionally powered submarine had demonstrated the ability to threaten the most powerful surface warship ever built.
This event challenged longstanding assumptions within the U.S. Navy about undersea warfare and carrier invulnerability.
To an equal or greater extent, the wargame’s findings reinforced the importance of the cost curve, as a less expensive single submarine sank a $13 billion carrier.
Pacific Ocean (November 3, 2003) — During Tiger Cruise aboard USS Nimitz (CVN 68), Nimitz and Carrier Air Wing Eleven personnel participate in a flag unfurling rehearsal with the help of fellow tigers on the flight deck. The Nimitz Carrier Strike Force and Carrier Air Wing Eleven (CVW-11) are in route to Nimitz homeport of San Diego, California after an eight-month deployment to the Arabian Gulf in support of Operation Iraqi Freedom. U.S. Navy photo by Photographer Mate 3rd Class Elizabeth Thompson
Several factors contributed to Gotland’s success. Its low acoustic signature made it difficult for sonar operators to distinguish it from background noise.
The aftermath of the exercise was arguably more important than the simulated attack itself.
The U.S. Navy used the experience to reevaluate the anti-submarine tactics and technologies it was employing with its Carrier Strike Groups.
The Navy not only re-examined its sensor technology, such as Variable Towed Array Sonar, but also refined its training methods. Greater emphasis was placed on detecting and tracking.
Future of Sonar
The incident also influenced broader strategic thinking. It underscored that advanced military power does not always require the largest or most expensive platforms.
Smaller nations operating modern conventional submarines could pose serious threats to even the most sophisticated navies.
For the United States, this reinforced the importance of preparing for asymmetric warfare, where adversaries exploit specific weaknesses rather than matching strength for strength.
The 2005 war game involving HSwMS Gotland and the USS Ronald Reagan did not result in the literal sinking of an aircraft carrier, but it did deliver a powerful symbolic blow.
The U.S. Navy aircraft carriers USS Nimitz (CVN-68), USS Theodore Roosevelt (CVN-71) and USS Ronald Reagan (CVN-76) underway in the Western Pacific on 12 November 2017. The strike groups were underway and conducting operations in international waters as part of a three-carrier strike force exercise. This was the first time since August 2007 that three U.S. Navy carriers operated together. In 2007, USS Kitty Hawk (CV-63), USS Nimitz (CVN-68) and USS John C. Stennis (CVN-74) participated in exercise “Valiant Shield”.
By achieving a simulated kill during the exercise, the Swedish submarine exposed vulnerabilities in U.S. naval defenses and helped reshape American anti-submarine warfare priorities.
The event remains a frequently cited example of how realistic training and unexpected opponents can provide invaluable lessons—ones that may ultimately save lives and ships in real combat.
About the Author: Kris Osborn, Warrior Maven President
Kris Osborn is the President of Warrior Maven – Center for Military Modernization. Osborn previously served at the Pentagon as a highly qualified expert in the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Masters Degree in Comparative Literature from Columbia University.
