To be fair, the threat of super-stealthy diesel submarines being deployed around the world has been present for decades. Still, newer boats are coming armed with advanced anti-ship weapons and are being combined with new air-independent propulsion systems (AIP) making them near impossible to find in the ocean's depths—a one-two punch that can’t be ignored.

There is no force patrolling the world’s oceans more powerful than the mighty U.S. Navy. Washington’s nuclear-powered attack and ballistic submarines, aircraft carriers and surface combatants, all guided by the best trained sailors and professionals in the world, are no match when stacked up on paper one-on-one against the likes of Russia, China, Iran or any other challenger. And as history shows, going to war against Washington in a fair-fight is suicide. However, thanks to advances in modern, ultra-quiet conventional diesel-electric submarines, Washington will need to adjust its tactics if it were to tangle with any nation sporting these increasingly sophisticated weapons of war.

Recommended: Who Swallows North Korea after it Collapses? 

To be fair, the threat of super-stealthy diesel submarines being deployed around the world has been present for decades. Still, newer boats are coming armed with advanced anti-ship weapons and are being combined with new air-independent propulsion systems (AIP) making them near impossible to find in the ocean's depths—a one-two punch that can’t be ignored.

(This first appeared in 2016.) 

Recommended: US Army's 5 Most Lethal Weapons of War

Recent history shows only too clearly the challenge the United States and other modern navies are facing from these heavily armed, ‘stealth’ submarines. Back as far as 2005, the U.S. Navy recognized the challenge and reached out to friends and allies for help. It was that year that the HMS Gotland, a modern AIP submarine serving in the Swedish Navy, made its home in California for a year. The goal was to test the impact of such a boat against U.S. aircraft carrier battle groups and other important vessels. It seems the boats, much cheaper to produce than the standard American nuclear-attack subs, created quite the stir:

“Apparently the Navy got more than they were bargaining for when it came to finding and engaging the stealthy little sub. The Gotland virtually ‘sunk’ many U.S. nuclear fast attack subs, destroyers, frigates, cruisers and even made it into the 'red zone' beyond the last ring of anti-submarine defenses within a carrier strike group. Although it was rumored she got many simulated shots off on various U.S. super-carriers, one large-scale training exercise in particular with the then brand new USS Ronald Reagan ended with the little sub making multiple attack runs on the super-carrier, before slithering away without ever being detected. . . ”

“. . .the little Swedish sub was "so silent it literally did not exist to our sensors."

Thankfully the above were controlled exercises, crafted for America’s ‘silent service’ and surface combatant operators to understand the threat they were dealing with. However, not all encounters with ultra-quiet diesel boats have been as friendly—or just a mere exercise. Back in 2006, a Chinese Song-class attack submarine, created at least partially by Russian and Western technology and likely not nearly as advanced as the Gutland (the Song-class does not have AIP technology, for example) tailed the Japan-based U.S. Navy aircraft carrier USS Kitty Hawk in the East China Sea near Okinawa without being identified. While such a shadowing operation is quite normal, the sub “surfaced within five miles of the carrier, in deep waters off Okinawa, and only then was it spotted, by one of the carrier's planes on a routine surveillance flight.” Such submarines are armed with advanced anti-ship missile and wake-homing torpedoes.

Recommended: Russia's Armata Tank vs. America's M-1 Abrams - Who Wins?

Moving to the present, Russia seems to be doubling down on its development of these important vessels. Moscow is developing an even deadlier class of boats:

“The stealth capabilities of Russia’s new Lada-class diesel-electric submarines far exceed those of their predecessors, Admiraty Shipyard’s CEO Alexander Buzakov told the Russian press.

“According to Buzakov, the new vessels are even stealthier than Russian Kilo-class submarines, thought to be one of the quietest diesel-electric submarine classes in the world and dubbed "black holes" for their ability to "disappear” from sonars.

“The new submarines are able to maintain such a low profile thanks to a clever implementation of a next-generation anti-reflective acoustic coating and a new improved hydro-acoustic system, Buzakov said.

He also added that during the new submarines’ construction and design process, the development team managed to gather a lot of valuable data which, among other things, allowed them to significantly improve the Kilo-class submarines as well.

“The Lada-class submarines are designed to defend coastlines against ships and other submarines, gather intelligence, provide surveillance and reconnaissance missions, and act as a mother ship for special forces. With its new air-independent propulsion plant, a Lada submarine can remain submerged for as many as 25 days. With its vast array of weapon systems, the Lada is also world’s first non-nuclear submarine to be equipped with specialized launchers for cruise missiles.”

So, with all this being said, what should the U.S. Navy do about this challenge? A greater investment in anti-submarine warfare would be a great place to start. New detection methods could also help, although such methods could also be used against Washington’s subs. Here’s an idea: maybe America should get in on the act and get some of its own? Hmmm. . . 

Harry Kazianis (@grecianformula) is Director of Defense Studies at the Center for the National Interest and Executive Editor of its publishing arm, The National Interest.