The key
to understanding this post is grasping and accepting that the engagement window
for a ship to defend against attacking missiles will allow just 4 shots per
target (see, “Engagement Range”). Most
of us have grown up seeing WWII videos of ship anti-aircraft gunners pouring
thousands of rounds into the air as the enemy planes slowly approach and then
enter their terminal dives and weapon releases.
Each target engagement can last for several minutes. This is no longer the case.
While I
view history as timeless in its lessons, irrespective of technological
advances, this is an example where technology has altered the details, if not
the fundamental concept.
Each
target engagement will last 4 shots. It
doesn’t matter how many missiles you have in your magazine, you’ll only get 4
shots per target. If you don’t
understand this, there’s no point reading the rest of the post. This is not an opinion on my part, this is
simple and pure physics.
With
that out of the way …
One of
the problems that has become obvious over the course of many posts and comments
is that most people do not understand the concept of escort vessels. Really?
What could be more simple, you say?
You assign a couple of Burkes to provide anti-air (AAW) protection and,
of course, being multi-function, they have the added benefit of being able to
provide anti-submarine (ASW) protection, as well ! Well, there’s a little more to it than that. In fact, there’s a lot more to it than that!
Unfortunately,
far too many observers/commenters believe that around 2-4 escorts is sufficient
for a high value target (HVU) like a carrier, convoy, or amphibious group
because that’s all they’ve ever seen the Navy operate. The more extreme observers might call for 6-8
escorts. However, even this is woefully
insufficient and now we’re going to see why and we’re going to correct this
misconception.
As
always, let’s begin with a review of history.
Historical Escorts
We
forget just how many escorts a WWII carrier task force required. Admiral Marc Mitscher described the escort
requirements of a carrier task force in the following statement from Wikipedia.
Said Mitscher: “The ideal composition of a fast-carrier task
force is four carriers, six to eight support vessels and not less than 18
destroyers, preferably 24. More than four carriers in a task group cannot be
advantageously used due to the amount of air room required. Less than four
carriers requires an uneconomical use of support ships and screening vessels.”
(1)
The
support vessels were cruisers and battleships.
Combined with 18-24 destroyers, the total escort requirement was 24-32
ships – a quantity that seems shocking to us, today, because we’ve forgotten
the requirements of combat.
Having
reminded ourselves of the historical precedents, let’s conduct an analytical
examination of today’s requirements.
Escorts are needed to perform two basic functions: anti-air protection and anti-submarine protection. Additional functions such as electronic
warfare and anti-surface protection are also required but can generally be
performed by the AAW or ASW vessels.
Anti-Air (AAW) Escorts
There
are several aspects to consider when discussing AAW escorts.
Threat
Axis. Unless you have absolute knowledge about the
enemy’s attack plans – and you never do – the threat axis is unknown. Yes, you may well have a general idea of what
direction an attack will come from but a ‘general idea’ is far from
certain.
In
WWII, the identification of the threat axis was a bit more obvious. While aircraft could, and did, attempt to
circle around and try to approach from alternate or several angles, their
ability to do so was limited by their range.
Attacking aircraft were generally near their maximum range by the time
they reached the target and began their terminal attack runs so they rarely had
the fuel required to perform wide swings around their targets to approach from
unexpected directions. Additionally,
wide swings provided more time for the defensive aircraft and AAA to attrite
the strike so the strikes generally made fairly straight approaches with just
some terminal maneuvering, especially for torpedo attacks.
Today,
cruise missiles with thousand mile ranges can use waypoints to approach from
any angle. Therefore, every axis is a
potential threat axis although more direct axes still have a somewhat higher
likelihood of attack.
So, to
cover ever axis requires that the escorts be arranged evenly in a circle around
the high value unit they’re escorting.
This, alone, would suggest the need for at least a dozen or more
escorts.
Effective
Engagement Range. We’ve previously discussed that the most
likely AAW engagement scenario involves sea skimming aircraft or missiles that
are detected at the radar horizon (call it 20 miles, optimistically) (again,
see, “Engagement Range”) and that engagements
will involve short/medium range ESSM missiles with very brief engagement
windows. Two salvos of two missiles each
would be a fortunate engagement. That
being the case, those marvelous ships with a thousand VLS cells are pointless,
as we’ve pointed out in the past. Each
ship, regardless of how many VLS cells it has, is likely to only get off four
defensive missile shots per engagement.
That being the case, it is obvious that the only way to get more
missiles into the engagement is to have more ships since more VLS cells per
ship doesn’t help. This, again, suggests
the need for as many AAW escort ships as possible. Thus, one would like to have 2-4 ships along
every threat axis. The arithmetic on
this quickly leads to very large escort numbers.
Probability
of Kill (pK). It’s necessary to consider the defensive pK
against attacking missiles when trying to determine the required number of
escorts. For example, if the pK is very
high, you only need a few escorts because you only need a few defensive
missiles but if the pK is very low then you need lots of escorts to make up for
the individually low pK (recalling that each ship will only get a very few
shots per engagement).
So,
what is the pK? Well, that depends in
great measure on the geometry of the intercept.
If the attacking missile is coming straight at you, then the geometry is
simple, your defensive missile is not required to maneuver, and the pK is
high. At the opposite extreme, if the
missile is going past you (nominally, a 90 degree off-axis defensive shot),
aimed at some other ship/target then the pK is going to be very low because
off-axis shots require a great deal of maneuvering by the defensive missile.
The
reality is that modern attacking missiles, even one coming straight at you,
enter into wild, violent, evasive maneuvers in the terminal attack phase
precisely to make the defensive shot a somewhat off-axis shot and, thus, a
lower pK.
There
is very little data available on actual naval defensive missile engagements and
what there is, is not encouraging.
Historically, the pK of defensive missiles, even against direct attacks,
is 5%-25% (see, “AAW”).
It’s
readily apparent, then, that if the escort is not the main target, which it
usually isn’t, the defensive pK will be very low which requires that multiple
escorts be placed as nearly on the direct threat axis as possible. The only way to ensure direct threat axis
placement is with large numbers of escorts distributed evenly around the
escorted target so as to ensure that there are at least some escorts in the
direct path of the attacking aircraft/missiles.
Layered
Defense. The best defense is one that begins as far
out from the HVU as possible. Recognizing
that the most likely engagement will occur at radar horizon distances (15-20
miles), the only way to push the initial engagement out from the HVU is to create
multiple defensive layers of escorts spaced at 15-20 mile intervals out from
the escorted high value unit so that the attacking aircraft/missiles have to
pass through multiple layers and multiple engagement opportunities in order to
get to the HVU.
We did
this in WWII with distant rings of destroyers backed by closer rings of
cruisers and, finally, a very close ring of battleships (the WWII equivalent of
Aegis). To get, say, three rings
requires a radius of 45-60 miles which means a 90-120 mile diameter defensive
sphere around the HVU! When one
contemplates the number of ships required to attain effective engagement
density across a 90 mile diameter defensive circle and still cover every threat
axis, it becomes instantly apparent that many, many escorts are needed.
Positioning. Modern aircraft and missiles are far too fast
to allow for escort repositioning once an engagement has begun. Whatever position the escorts are in when an
attack begins is the position they’ll have to fight from. Thus, we must have enough escorts to provide
adequate protection from any axis.
Repositioning during an attack is not an option.
Anti-Submarine (ASW) Escorts
If the
ASW function resides on ships separate from the AAW function then the escort
requirement further increases.
Engagement
Range. Modern subs have torpedoes with ranges of up
to 60 miles. It is vital to detect and
engage subs beyond their torpedo range to the HVU. That means engaging at ranges of 60+
miles. Given the slow pace of ASW
engagements, great standoff distance is also necessary to allow the HVU to
continuing advancing while the ASW engagement is being conducted. If ASW engagement begins at, say, 20 miles,
the HVU would have to immediately turn away and begin a high speed run in the
opposite direction. This is
counterproductive in getting the HVU to its destination.
Subs
also have guided missiles with ranges of a hundred miles or more although this
becomes an AAW problem at some point.
Numbers. WWII demonstrated that the most important
factor in successful ASW was numbers of ASW assets. The Cold War simply reinforced this
lesson. Thus, having a single ASW escort
in any engagement is unlikely to produce a positive result. Successful engagements will require multiple
ASW assets. Now, not all of the numbers
need to be ships. Some/all of the assets
can be aircraft but, ultimately, the aircraft require ships to operate from.
Threat
Axis. Unlike the aerial threat, submarine threat
axes are much more limited and are primarily centered around the course of the
advancing HVU. Subs that are
significantly offset from the course of advance will be unable to achieve a
viable intercept position without significantly increasing speed and making
their presence known. Thus, while a few
flank and rear ASW escorts are needed, the majority can be concentrated along
the forward arc of the direction of travel.
Electronic Warfare (EW) Escort
We
should have a few dedicated EW escorts.
Our current ships are limited to small, underpowered SLQ-32 / SEWIP
components that are designed to provide self-defense, only. A dedicated, high powered area defense EW
ship is needed that can operate antennae as large as needed and as many as
needed along with numerous, high powered transmitters for jamming. Think of this as the EW version of Aegis.
We use
dedicated, large EW aircraft so why not ships?
Compare the size of even aircraft EW equipment to ship EW equipment and
it becomes immediately obvious how meager our shipboard EW is.
Attrition
Another
factor in escort number determination is attrition. Some extra escorts are necessary to allow for
possible losses. Without some extra
escorts, the entire group would be forced to retire upon the first loss of an
escort.
Escort Concept
Having
considered the above requirements, let’s see if we can bring it all together
and conceptualize an escort requirement.
We’d like to have multiple defensive rings similar to the following:
Escort Concept
|
Defensive Ring
|
Radial Distance, miles
|
No. of Escorts
|
Purpose
|
Inner
|
1
|
4
|
engage
leakers
|
Second
|
20
|
18a
|
main
engagement zone
|
Third
|
35
|
8b
|
early
warning / early engagement
|
Fourth
|
60
|
8c
|
ASW /
early warning
|
a each ship covers a 20 deg sector
b each ship covers a 45 deg sector
c ships spread across 45 deg arc on course of advance
This
gives us three engagement zones plus a distant ASW zone using a total of 38
escorts. Most of you will be stunned at
the number but it’s an historically and analytically supported
requirement. We’ve just forgotten how
many ships are needed to form a survivable, defensible group.
Another
aspect that leads to larger escort requirements today is the increased range
and speed of attacking weapons (aircraft and missiles). In WWII, aircraft had to basically overfly
the target ship to release weapons and their speed of approach was only around
two hundred miles per hour which provided extended engagement windows (time)
for the defenders. With today’s weapon’s
range and speed and the resulting short engagement windows, the only
compensation is to engage further out and with more escorts.
This
immediately leads one to wonder why the Navy never exercises with this kind of
escort density. Hey, it’s peacetime – I
get it. There’s no need to provide that
level of escort on a routine, peacetime basis.
But, shouldn’t we be exercising this escort concept on a regular basis
so that we know how to do it when war comes?
I guarantee you that none of our current admirals or captains have the
slightest idea how to manage a wartime escort group, where to place the
escorts, what tactics to use, or how to maneuver a large, spread out
group.
Consider
the ASW escort challenge … What will the
rest of the group do if a submarine is detected? Keep going?
Turn away? How many escorts
should engage? Can we afford to detach
escorts for prosecution of the target?
How do we compensate if we detach escorts? This is the tactical level of control that
none of our naval officers have any grasp of and never will since we don’t
practice it. We’re going to wind up
learning the hard way when war comes and the price of that learning will be
sunk ships and lost crews all because the Navy refuses to conduct serious
combat exercises now, during peacetime.
Note
that the above only applies to a single HVU or a closely clustered group of
HVUs. For a wartime group of 4 carriers,
the carriers themselves will be separated by 5-10 miles so the size of the
defensive rings and the number of escorts would have to be adjusted accordingly
– something we should be learning about in exercises but aren’t.
We also
have to make adjustments for reality.
While we might like to have thirty or fifty or hundred escorts, if we
only have, say, 15 available then we have to modify our thinking. Part of that modification might be to cancel
missions that have inadequate escort availability. Alternatively, we might have to sail with
lesser numbers of escorts. How do we
adjust? Where do we place our limited
escorts? How does inadequate numbers
affect our tactical usage of the escorts?
These are the types of scenarios we should be exercising and learning,
now, during peacetime, instead of wasting our time on useless deployments to
show the flag or chase pirates in skiffs.
We are wasting this valuable peacetime.
 |
| Fletcher Class Destroyer |
Finally,
let’s compare our potential existing escort strength to the conceptual needs
we’ve just described. We have around 80
Burkes/Ticos so we can fill out two task forces – and that’s before we’ve lost
any ships to combat. Are two task forces
enough to conduct a peer war? I don’t
think so. Compare that to WWII when we
built 175 Fletcher class destroyers, alone, and many dozens of cruisers and
battleships. Of course, we also had
hundreds of older destroyers and destroyer escorts and, as the war went on,
another hundred or so of newer Sumner/Gearing class destroyers. We’re not even close to that level,
currently, nor should we be. We didn’t
have all those ships when WWII started.
We built them rapidly as the war progressed. The problem is that we no longer have the
ability to rapidly build up ship numbers.
We lack the shipyards, the work force, and, worse, our designs have
become so complex that it requires years to build a single Burke class
destroyer. We absolutely need to revisit
our entire warship design philosophy with an eye towards simplifying it for
rapid mass production.
All
right, there you have it. You now
understand the role of escort ships and you have some idea of how many are
needed and how they should be used. For
the Navy, it’s now time to start exercising these concepts and finding out what
works and what changes need to be made.
We also need to start developing combat commanders who have actual
command experience with large escort groups.
Peacetime is a precious commodity – it’s the time to prepare for war and
we’re squandering it with worthless deployments, pirate chases, and flag
waving.
_________________________________
(1)Wikipedia,
“Fast Carrier Task Force”, retrieved 4-May-2020,
https://en.wikipedia.org/wiki/Fast_Carrier_Task_Force
