A Dutch submarine once slipped through the defenses of a U.S. carrier strike group and scored a simulated hit on the carrier itself, a result that still carries weight far beyond a single exercise. The platform was HNLMS Walrus, a diesel-electric boat that used stealth rather than speed to reach firing position during a 1999 NATO exercise. In the simulation, it penetrated a defensive screen built around USS Theodore Roosevelt, a formation designed to layer protection through escorts, aircraft, helicopters, and submarines. The headline contrast was stark: a much cheaper undersea platform challenged one of the most expensive and symbolically important formations in naval power.
The deeper lesson was not that carriers had become obsolete. It was that anti-submarine warfare remains brutally unforgiving when detection fails. A carrier strike group can be optimized against missiles, aircraft, and surface threats, but an ultra-quiet conventional submarine in cluttered coastal waters creates a different problem set. When diesel-electric submarines run on battery, they can become exceptionally difficult for passive sonar to pick up, especially in noisy shallows, crowded shipping lanes, and littoral terrain where sound behaves unpredictably. That is why littoral anti-submarine warfare remains one of the hardest naval missions to execute consistently.
The Walrus case was not isolated. In later exercises, Sweden’s Gotland-class submarine produced similarly uncomfortable results against U.S. naval forces. Those episodes reinforced a reality that naval planners have known for generations: a submarine does not need to dominate the sea to alter it. It only needs to remain hidden long enough to force caution, change routing, delay operations, or threaten the highest-value ship in the formation.
History gives that logic a much larger frame. During World War II, Allied submarines in the Pacific helped cripple Japan’s maritime logistics, and U.S. submarines were credited with 56% of Japan’s merchant marine losses. The strategic pattern is familiar even if the platforms have changed: submarines impose outsized costs because they attack where fleets, supply systems, and assumptions are least comfortable. For smaller navies, that asymmetry has long been attractive. Dutch submarine design reflected that thinking early, with the service fielding some of the first snorkel-equipped submarines and building a doctrine around undersea efficiency rather than surface mass.
That is why the modern carrier problem is really an integration problem. The U.S. response has been to rebuild anti-submarine depth across the force rather than rely on a single sensor or platform. Maritime patrol aircraft, improved sonars, helicopters, attack submarines, and unmanned systems now form a more distributed search architecture. The retirement of the S-3 Viking left a visible gap in carrier-based submarine hunting, and analysts have argued for restoring some of that reach with fighter-launched sensors and lightweight anti-submarine weapons. The logic is speed: if a submarine launches from long range, the response window shrinks fast.
That matters most in regions defined by chokepoints, island chains, and shallow approaches. Carrier strike groups still project air power at a scale few other systems can match, but they do not operate in an acoustic vacuum. The lesson from Walrus and Gotland is less about embarrassment than design pressure. Expensive fleets have to defeat inexpensive threats repeatedly, while the submarine only needs one opening. In naval engineering terms, that is the kind of imbalance that reshapes doctrine, procurement, and training for years.
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