In a 2005 joint training exercise, the Swedish submarine HSwMS Gotland successfully penetrated the defenses of Carrier Strike Group 7. It simulated the sinking of the USS Ronald Reagan, one of the United States Navy’s nuclear-powered aircraft carriers off the coast of California.
The Swedish ship managed to snap several photographs of the USS Ronald Regan, proof of its position and the fact that it had gotten to the heart of the Carrier Strike Group.
How the Gotland Snuck into Carrier Strike Group 7
Carrier Strike Groups, centered around aircraft carriers, use a mix of surface vessels like destroyers, frigates, and cruisers, as well as submarines and airborne assets to provide a thickly layered defense against a variety of threats.
Leveraging the eyes and ears, these assets make a Carrier Strike Group’s anti-submarine warfare, or ASW, capabilities prodigious. But despite this, the HSwMS Gotland managed to slip through Carrier Strike Group 7’s defenses undetected.
The key to the HSwMS Gotland’s ability to remain undetected, even within the Carrier Strike Group, is thanks to its air-independent propulsion, or AIP system, which allowed it to operate silently for extended periods.
Traditional diesel-electric submarines needs a surface or use a snorkel to feed oxygen from the air. Their diesel engines recharge their batteries and allow them to operate relatively silently underwater, making them quite vulnerable to detection when on the surface.
The HSwMS Gotland, however, relies not on diesel-electric technology but a Stirling AIP system that allows it to remain below the surface for weeks at a time while also running very quietly — and making the submarine hard to detect.
HSwMS Gotland: Design and Capabilities
The Gotland-class submarines, designed and built by Kockums for the Swedish Navy, were among the first operational submarines to incorporate an AIP system. This technology relies on liquid oxygen and diesel fuel to power their Stirling engines and generate electricity without the need to surface for much longer durations.
In addition, Stirling engines produce much less sound than traditional diesel engines, a further enhancement to staying hidden below the waves undetected.
Like other submarines, the HSwMS Gotland is armed with torpedos that can engage ships on the surface as well as other submarines.
Combined with its formidable stealth capabilities, the HSwMS Gotland’s abilities are formidable.
And given the HSwMS Gotland’s rather diminutive size compared to the larger American nuclear-powered submarines, it may have an advantage in shallower coastal waters.
U.S. Navy’s Response and Bilateral Training Agreement
Following the HSwMS Gotland’s surprise success against the USS Ronald Regan during the exercise, the need to improve the U.S. Navy’s anti-submarine warfare ASW capabilities became painfully obvious.
To that end, the U.S. Navy signed an agreement with Sweden to lease the HSwMS Gotland and its crew for a two-year training program in order to provide American sailors with actual, realistic training against a modern and affected AIP submarine.
The HSwMS Gotland-USS Ronald Regan incident was a stark wakeup call for the U.S. Navy.
Though all of the U.S. Navy’s submarines are nuclear-powered, the Swedish technology demonstrated that non-nuclear maritime propulsion technology could still pose a formidable threat to even the best-protected surface vessels.
It underscored the ongoing cat-and-mouse game of offense and defense in anti-submarine warfare.
Gotland-Class Submarine: A Photo Essay
Gotland-Class: Image Credit – Sweden.
Gotland-Class. Image Credit: Creative Commons.
Gotland-class submarine. Image Credit: Creative Commons.
Gotland-class Submarine.
Image of Gotland-class Submarine.
Gotland-class Submarine.
Gotland-class Submarine.
Gotland-class Submarine. Image: Creative Commons.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
