Full Spectrum ASW
William Toti
January 8, 2015
During the Cold War, the US Navy (particularly the submarine force) force specialized in, and excelled at Antisubmarine Warfare (ASW) against the Soviet Union. But with the demise of the Soviet Union, ASW was put on the back-burner as an activity irrelevant to modern warfare. Over a decade passed before submarines would again be considered a serious threat to national security. Over the course of that time the nature of the submarine threat changed, so when the Navy “rediscovered” ASW, it learned that traditional, sensor-based methods of fighting against submarines, while important, could no longer assure victory. To respond to this new threat, while head of doctrine and requirements for Fleet ASW Command, in 2005 I conceived a new approach, one that became known as “Full Spectrum ASW.”

The 2010 sinking of a South Korean corvette by an antiquated, supposedly obsolete North Korean submarine demonstrated one inarguable fact: that on any given day, any given submarine, no matter how crude or unsophisticated, can sink nearly any given surface ship.  This is something that most navies understand.  The problem is that because finding a submarine is so hard– sometimes nearly impossible– people have long assumed that defeating the submarine is equally difficult.

But modern methods have deconstructed this perception.  The “Rim of the Pacific” (RIMPAC) exercise in 2004 became a pivotal event in my development as an ASW theorist.  During that exercise, a remarkable thing was happening.  ASW forces were achieving small victories in their battles against submarines.  They just didn’t know it, because the ASW forces hadn’t actually detected the submarines and therefore couldn’t monitor their reaction.  Many of these successes were transitory, and not knowing that they had just done something that proved effective in their ASW fight, they were not sufficiently informed to realize that to extend their success, they merely had to repeat “that thing that worked without them knowing it worked.”

Similarly, while most of the ASW activity was focused on detecting, localizing, and “destroying” enemy submarines, many of the detection tactics that consumed nearly all of the friendly forces’ ASW effort simply did not work.  Most of the submarines remained undetected.  Yet, friendly forces were still achieving transitory ASW successes against submarines they had not even detected.

In other words, victory could be achieved through serendipity.

So in 2004, the driving question became this:  what if we could convert this serendipity into “effectivity,” and translate these accidental methods into deliberate tactics?

During the Cold War ASW was dominated by the acousticians, but by the 21st Century we had long since passed the point of diminishing returns on the ability to detect quiet submarines acoustically.  Hence, the “sensor uber alles” approach, although still regaled by the Cold Warriors, was no longer affordable nor effective.  We had to find a better way.  And in so doing, it quickly became apparent that it would be helpful to take into consideration a fundamental aspect of submarine operations that most ASW theories tend to ignore:  that submarines are manned by thinking human beings who, just like all other human beings, react to outside stimuli.  And while it was becoming increasingly difficult to detect a submarine, it was also true that the submarine crew usually could not tell whether they had been detected.  In that we found the lynchpin:  it is possible to shape a submarine’s behavior even when it hasn’t been detected.  That realization led to the precepts of Full Spectrum ASW.

The Precepts of Full Spectrum ASW

The fundamental issue at hand was this:  although it’s great fun to detect and destroy an enemy submarine, real ASW is not about detecting the submarine, it’s not about killing the submarine, it’s about defeating the submarine.  This is a nuance, but it’s an important nuance.

For example, you can operate in the vicinity of mines for months without destroying all of them.  All you really need to know is that there are no mines near you, that you have a clear path.  Undetected but irrelevant mines are merely a nuisance.

Well, diesel submarines can be thought of as smart, somewhat mobile, mines.  Most of the ships that find themselves the targets of diesel submarines can easily outrun and out-endure their nemesis.

Further, “defeating” a submarine is significantly easier than “detecting” it.  Detecting any submarine that could be a threat submarine requires a “boil the ocean” level of effort, in both technology and force structure.  To defeat the submarine, all you have to do is render it irrelevant.  Draw it out of firing position.  Cause its fire control solution to be wrong.  Cause it to go after the wrong target.  Render its weapons useless.

People generally think of submarines as having claustrophobic physical environments, and they do, but what they really have is claustrophobicsensory environments.  They are very limited in what they can perceive. Using acoustics, they generally have a maximum detection range of less than 50 miles.  They must be at periscope depth to use optical systems, but detection ranges for optical systems are limited by a very low periscope height of eye, and so are generally less than fifteen miles.  For real long-distance targeting they need intelligence or outside cueing, both of which can be denied to them by other means.

But more to the point, our Cold War remnant, sensor-focused ASW doctrine was causing us to miss many potential opportunities for soft-kill defeat.  Rather than applying our strengths against the enemy’s weaknesses, our Cold War tactics applied our weakness, open ocean detection capability, against the enemy’s strength—stealth.  An “Anti-Sun Tzu” approach.

What we really needed was something our ground forces are good at:  defense-in-depth.  Army combined arms tactics build kill zones, with different zones being serviceable by different types of weapons: air, indirect fire, direct fire, etc.

We needed something that addressed the submarine threat from that point of view, starting before the point where the subs departed their homeport.

We needed—and here’s that word again—a holistic approach.

So our team mapped out “the journey of a submarine,” considering what would be required to defeat the submarine in every phase of its journey, in every environment it transited.  We brainstormed these concepts for weeks, trying to find holes and additional opportunities.

What resulted was a nine-step process that we briefed to each of the numbered fleet commanders, to the Pacific Fleet Commander and to Fleet Forces Command.  A tenth step was added by the Pacific Fleet commander during our murder-board session with him.

This doctrine became known as the “Ten Threads of Full Spectrum ASW.”  Although they are summarized below, the specific solutions for each thread are not— both for reasons of classification, and because I don’t want to stifle innovation by providing what I think is “the right answer.”

The Ten Threads of Full Spectrum ASW

In the years since we had “rediscovered” ASW, Navy leaders throughout the chain of command had heightened the awareness of our ASW challenges by stating publicly, “we suck at ASW.”  This was not helpful.  Every time one of our admirals said this, another country bought a submarine.

The truth was that our ASW skills had atrophied.  The truth was we needed to get better.  But with apologies to Winston Churchill, our ASW skills were the worst in the world, except for all the rest.  We have the best ground force capability in the world, but that does not imply we should stop improving our Army and Marine Corps.  So it is with ASW.

There is a point to be made here.  One of the most effective forms of ASW is to stop the proliferation of submarines.  We have to convince adversaries that submarines are not the solution to their “American problem.”  And the only way we can do that is to tell the truth: that the use of submarines by an adversary might cause some tactical damage to American forces, but that use would cause much more severe strategic damage to the interests of the nation that employs the submarines, and this strategic self-mutilation would outweigh any tactical success that nation would achieve.

This led to the first thread of Full Spectrum ASW:

1. Create conditions where an adversary chooses not to employ submarines

As opposed to using submarines for intelligence-gathering, the decision to employ submarines in combat is a strategic decision.  What we really needed to do was create the conditions where the strategic cost-benefit analysis argued against a nation using submarines.  There are several ways to do this, most of which are not appropriate to discuss in an open forum.

But it’s also important that the submarine crew understand that if they are to go up against the United States in open naval warfare, there is a very high likelihood that they will not survive.  That submarine warfare against the United States is a kamikaze mission.  This is not dogma, it’s the truth.

It means that just as the Army and Marine Corps have demonstrated their lethality and success in land warfare, we must make sure any potential adversary understands the extreme peril they will put their submarine crews in should they choose to employ them— peril that is not counter-balanced by strategic advantage.  That the cost of submarine escalation is not outweighed by any potential benefit gained.  Sadly, this message has not been conveyed effectively to many of our adversaries.

But ASW doctrine needs more than just the deterrent component, there needs to be teeth in the “defeat” components as well:

2. Defeat submarines in port

Obviously, it’s always better to kill the archer (the home port) than the arrow (the submarine), so destroying a submarine before it gets underway, or after it returns to port for resupply, is an obvious required capability. This is also an opportunity to apply one of our current strengths—strike capability—against a weakness of any short-endurance diesel submarine—the need to resupply.

When I initially began to pitch Full Spectrum ASW, some reviewers tried to get me to drop this thread.  I frequently heard the argument, “Thread 2 will not pay any dividends because all of the enemy’s submarines will be underway before the war begins,” to which I would reply, only half joking, “Only if their funding of maintenance is better than ours.”

Thread 2 requires no new force structure, and it has the potential for high payoff, but only if we are postured to execute.  It requires the detection of alternate refueling and maintenance locations, and therefore brings with it a heavy actionable intelligence requirement.

Even if the submarines are underway before the war starts, they probably will not know precisely where to find their American targets absent external direction, which leads to:

3.  Defeat the submarines’ shore-based command and control capability

The ocean is a big place to look for an individual ship or strike group, even when you have a general idea of where a particular operation is taking place, particularly if you’re limited to a speed of ten knots to conserve battery capacity.  If we can deny submarines their non-organic (shore-based) C2 capability, this constraint becomes even more limiting.  Absent external targeting information, most submarines stumble around the ocean semi-blind.  Thread 3 therefore requires the capability to defeat the submarine’s shore-based command and control system.

It requires an ability to interfere with the enemy’s submarine communication systems, interfere with their ability to pass over-the-horizon targeting information to the submarines, and affect the enemy’s decision-making process for selecting the location for operations, even if only locally.

Which leads us to thread 4:

4. Defeat submarines near port, in denied areas

During the Cold War, one of our ASW precepts was that we would deny sanctuary to the Soviet submarine force.  We would go after them deep in their own waters, almost exclusively with our own SSNs. Today we must still maintain the capability to defeat submarines within their defensive perimeter, as they are leaving (or returning to) port.

It’s important to introduce a new concept here: the “vulnerability timeline.”  The vulnerability timeline is the period over which the enemy submarine will be vulnerable to being defeated during any particular thread of Full Spectrum ASW.  Our “design-to” solutions must be able to respond within the vulnerability timeline, otherwise they are rendered useless.   In the case of Thread 4, the vulnerability timeline for submarines leaving port would be on the order of minutes to a very few hours.  So our capability to engage enemy submarines in Thread 4 must possess this kind of responsiveness.  If the submarines do get underway in the early phases of the campaign, this means we will not have a lot of time to prepare the battlespace.  It means we have to be postured to execute Thread 4 in “enemy defensive areas,” even before actual hostilities begin.

Here we must also introduce the notion of “environment-tailoring.”  In short, each Full Spectrum ASW defeat mechanism must be tailored to the specific real-world physical environment in which it is intended to work.  A hypothetical, generic “capabilities-based” ASW solution is neither affordable nor required, because there is a limited number of countries that can actually pose a submarine threat to the United States.

Hence, the solutions we might use for the “defeat near port in denied areas” are very different from the solutions we might use for the next thread of Full Spectrum ASW:

5. Defeat submarines in choke points

In the real world, most adversary submarines have to transit through choke points in order to threaten U.S. forces.  These choke points serve as funneling locations that constrain the area we would need to search.  These choke points are usually not in denied areas.  Hence, less “survivable” solutions can be used to submarines in these areas.

A solution to Thread 5 of Full Spectrum ASW would require both very shallow water detection and a very shallow water attack, and could employ land-based solutions of limited range (the width of the choke point).  The vulnerability timeline for Thread 5 is the time it takes the submarine to transit the choke point, on the order of minutes to a very few hours.

Once the submarine has transited the choke point, then we’re onto Thread 6, a domain where the ASW problem potentially becomes much harder:

6. Defeat submarines in open ocean

Most of our post-Cold War ASW tactics and capability development, and almost all of our money, has gone into solving the Thread 6 ASW problem without context or balance.

Thread 6 is about deep water ASW.  It is where the ASW fight transitions from offense to defense.  It requires the ability to conduct broad area search over vast expanses of ocean. Many of our current capabilities, including SURTASS and Low Frequency Active Acoustic, directly (and only) address Thread 6.

Thread 6 is about defeating the submarines before they get into firing position.  (While thread 6 is transitionary, the purely defensive ASW capability against submarines that are in firing position is factored into Thread 9.)  The vulnerability timeline for Thread 6 is the several hours to the few days required for the submarine to close to firing position.

A robust Thread 6 capability also depends on an effective ability to execute Thread 7:

7.  Draw enemy submarines into ASW “kill boxes,” to a time and place of our choosing

Repeating the theme that it’s very difficult for submerged submarines to separate the good contacts from the bad (absent visual cues), conversely, it’s relatively easy to draw a submarine to the wrong “contact.”  If that “contact” happens to be a trap, even better.  The submarine must be inundated by so many “targets” that it becomes nearly impossible for him to separate the signal from the noise.

Further, if the submarine crew knows that the vast majority of targets they detect with organic sensors will be false targets intended to draw them into kill boxes specifically designed to destroy them, that knowledge will modulate the crew’s behavior in many desirable ways. As with Thread 6, the vulnerability timeline for thread 7 is several hours to a few days.

So while Thread 7 endeavors to draw submarines away from our actual forces, it fits hand in glove with Thread 8:

8. Mask our forces from submarine detection or classification

The more false targets the submarine encounters, the harder it is for the submarine to separate the signal from the noise, and the easier it is to mask the actual targets from detection or classification.  Thread 8 is not about doing the impossible; it’s not about rendering large surface ships acoustically or electromagnetically invisible.  Rather, it is about increasing the fog of war by making the real targets look like anything but a real target.

There isn’t really a vulnerability timeline for Thread 8 because it affects our vulnerability to attack, rather than the enemy’s vulnerability.  Hence, Thread 8 must be a continuous process.

Which leads to Thread 9:

9. Defeat the submarines in close battle

In 2004, most post-Cold War ASW training started at step 9 of a 10-step process.  But we absolutely still need to defeat submarines in close battle—within the submarine’s weapon range.  Thread 9 has a very short vulnerability timeline, from seconds to a few minutes, before the submarine’s fire control solution would support weapon engagement.  Hence, the systems that allow us to defeat a submarine in close battle are very different from the systems that provide us the best capability to defeat submarines in the broad expanses of open ocean.  Thread 9 includes methods to detect (and defeat) submarines as they approach their torpedo launch point.  It also includes the ability to change the rhythm of battle by forcing the submarines react to torpedo attacks, real or imagined.

Which leads us to our last thread of Full Spectrum ASW:

10. Defeat the incoming torpedo

Assuming all the above fail, if a torpedo is launched, we must render it ineffective. As with Thread 9, the vulnerability timeline (this time we’re measuring the vulnerability of the incoming torpedo, not the submarine) is seconds to a very few minutes.

The End-Game

Over the course of first six weeks of 2005, Full Spectrum ASW was briefed roughly thirty times to various Navy leaders. At the time, I worried these concepts would encounter a great deal of resistance.  There were still a lot of unreformed Cold Warriors on active duty, folks who had not spent any time on modern real-world missions and just didn’t understand that the world of submarine warfare had changed significantly since the 1980s.  I understood their perspective because I also deployed on my first missions during the Cold War.

But as it pertained to thoughtful Navy leaders, my fears simply were not justified. Full Spectrum ASW was universally and almost immediately adopted by the 7th, 2nd, 3rd, and 5th Fleet commanders, by Pacific Fleet, and by Fleet Forces Command.  Then in March 2005, it was declared to be Navy doctrine by CNO Admiral Vern Clark.

It was later established as the foundation of the Navy’s Global ASW Concept of Operations, factoring in issues like the roles of various platforms, command and control relationships between ASW commanders, and basic tactics, techniques, and procedures.

In 2007 Fleet ASW Command morphed into the Naval Mine and ASW Command (NMAWC), taking on the mine warfare mission as well.  Following that transition, NMAWC initiated the development of “Full Spectrum Mine Warfare” to mirror Full Spectrum ASW.

Looking back, it’s hard to believe that the initial concepts of Full Spectrum ASW were crafted over a period of three or four days in December 2004, by a team of less than 15 people.  The lesson here is that properly focused, small “red cell” team activity can make a big difference, sometimes even over short periods of time.