The Truth About The Growing Diesel Submarine Threat From A Veteran Sub Hunter


Fighting a diesel submarine is potentially easy, but assuredly difficult.

Don’t care for the contradiction? Too bad! Welcome to anti-submarine warfare, or ASW.

The diesel! It is very interesting to see the media coverage of the diesel submarine threat and how impossible it will be to find air-independent propulsion (AIP) submarines. It’s as if we have been thrown back to the dark days of early 1942, when Nazi U-boats began operating off the U.S. East Coast and the Gulf of Mexico. One of my favorite alarmist headlines reads:

NATO Calls This Russian Submarine the “Black Hole” for 1 Terrifying Reason

There is no question that searching for a diesel submarine operating on batteries is very difficult, due to the nature of its signature (or, for the most part, non-signature). I was a sensor operator (SENSO) on S-3 Vikings starting in the mid-1980s, and I spent a lot of time looking for submarines of all kinds. On board a carrier, my Viking squadron’s aircrew chief petty officer loved to remind everyone in our ready room, flashlight in hand, about the challenge we faced as we were about to go into any major submarine-hunting exercise that included diesel boats, which was an extremely rare event. Turning it on, he said: “This is what a diesel sub sounds like.” The silence produced by the device and his comment was deafening.

However, the silence of a diesel submarine is not deafening. 

USN/National Archives

An S-3B Viking with its magnetic anomaly detector (MAD) deployed. The author hunted submarines during the Cold War as a crewman aboard Vikings. 

I’m amazed at how many of us forget that two world wars were successfully fought against diesel submarines. Then, as the first decade of the Cold War progressed, we relearned how to fight the diesel submarine’s technological advancements — namely, the snorkel and hydrodynamic streamlining. 

Notice I said “signature” above, which implies someone is trying to track a diesel submarine with passive sonobuoys. The first sonobuoys, introduced during World War II’s final years, had relatively good success into the 1950s at tracking diesel-boat propeller noises when the operator turned up successive buoys and listened for the one with the loudest propeller noise. As diesel boats became more streamlined and propeller-blade technology progressed, dropping passive buoys after a target submerged did not work as well. Basically, better boats moved faster than NATO aircraft and ASW ships could drop, tune, and listen to the buoys. Thankfully, active sonobuoy technology was just coming of age, and we were back in the game. Along with active sonobuoys, helicopter dipping-sonar technology was rising to the occasion, and a new fixed-wing/rotary-wing hunter-killer team rose with it. 

Operationally, no one in the mid-to-late Cold War attempted to track a submerged diesel submarine passively (where hydrophones listen without the help of any active sonar pulses). That non-use may be contributing to the fearful awe in which we hold diesel submarines today. 

Hunting Nukes Vs Diesels During The Cold War

Tracking a nuclear submarine can be relatively easy, depending on how noisy it is. As a lot of open-source material makes clear, nuclear boats always have some form of machinery running. The U.S. Navy and its allies learned early on just how noisy such a submarine can be. There is a great story about how easily SOSUS—the vast U.S. undersea sonar tracking network—detected and tracked the world’s first nuclear-powered submarine, the USS Nautilus (SSN-571), when it made its initial voyage across the Atlantic. It stunned the Navy. From then on, the service worked hard at silencing techniques that would make its boats the quietest in the world. The Soviets, on the other hand, took far too long to appreciate the need for silencing, focusing instead on perfecting their troubled reactors.


A US Navy P-3 Orion over a Soviet Victor I class nuclear submarine. Hunting ‘nukes’ is something of a different artform than hunting diesel-electric submarines.

Passive sonobuoys became the way to track nuclear submarines during the latter half of the Cold War. Once you gained contact with a search pattern of buoys, you then localized and tracked the target with an ever-decreasing number and narrowing pattern. This worked very, very well, particularly against noisy Soviet submarines. Reliance on this method, however, would become a liability by the time the Cold War came to an end.

Dropping active sonobuoys on a nuclear submarine was not normal. Doing so would only be used as a last resort, either to refine an attack or as an act of desperation if the damn thing pulled a fast one and disappeared! On the other hand, using active sonobuoys against a nuclear boat could be a planned aspect of an ASW exercise, but time “on top” of a U.S. submarine was precious and rare. In my own experience working with U.S. boats—mostly of the 637/Sturgeon class—I don’t recall ever dropping an active AN/SSQ-62 DICASS buoy on one from my S-3 Viking. 

It was almost unheard of to use active buoys against a Soviet nuclear-powered submarine. There’s a Cold War ASW legend that said using active was considered an act of war. I haven’t been able to find anything to support this, but it’s what we were told. I said “almost unheard of,” however. Despite the warning, sometimes permission was given, and it was a great tool to go active on a Soviet boat just to annoy the hell out of them. I never did this, but I have heard the stories of others who did.

A major problem for the U.S. Navy during the Cold War was training. As the nuclear-powered navy took over, diesel submarines quickly attained pariah status, much as propeller-driven aircraft did in the wake of the jet age.

After the Navy’s three Barbel class diesel submarines were decommissioned in the late 1980s — a decision solidified by the tragic fire aboard the USS Bonefish (SS-582) in the spring of 1988 — that was it; no more U.S. diesels. This myopic view affected how well-trained our ASW forces — including nuclear submarines — were when facing a diesel boat in the latter part of the Cold War. 

Sadly, I never got a chance to work with one of the Navy’s remarkable diesel subs. I felt completely inadequate with my training and understanding of how to hunt one using active sonobuoys. Even extensive time in the S-3 Viking Weapons Systems Trainer (WST) just did not prepare me for the realities of the active acoustic environment. I shudder every time I think about how poorly I would have done in a shooting war against a Soviet diesel boat. 

Department of Defense

An aerial starboard bow view of a Soviet Golf II class diesel-powered ballistic-missile submarine underway in 1985.

Since the end of the Cold War, the Navy has refused to seriously consider the need for a non-nuclear boat. The lack of such submarines, particularly U.S.-owned and operated ones, hinders effective training, which continues to be an embarrassment for the U.S. Navy as it confronts the rise of China, a resurgent Russia, and the continued proliferation of diesel/AIP submarines. 

Oddly enough, on rare occasions, U.S. nuclear submarines try to compensate for the shortfall by running their auxiliary diesel generators for ASW forces while on the surface or pretending to snorkel to simulate a diesel boat. But let’s be honest, that simply doesn’t approach the reality of going up against the genuine article.

Dispelling Myths

So, how much of a myth is it that diesel submarines are impossible to find and then track? 

The problem begins with trying to find a diesel submarine. The Atlantic Ocean’s underwater network of passive acoustic arrays — the SOund SUrveillance System, commonly known as SOSUS — was the Navy’s canary in the oceanic coal mine. It was originally designed to detect diesel submarines operating their main engines while snorkeling or surfaced. First-, second-, and even third-generation Soviet diesel boats, transiting into the Atlantic from the Soviet Northern or Baltic Fleets were relatively easy to detect….


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