The Doctrine of Incremental Reduction

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If you know the detailed capabilities of the Navy’s various antisubmarine warfare air­craft, ships, submarines and shore installations, and how they can be operated in co-ordina­tion against a large and varied submarine threat, you are a member of a small but grow­ing professional group. We have in the Navy today only a few officers who are well qualified in all phases of ASW, and these officers who have had, let us say, three or four tours of duty in ASW, voluntarily or involuntarily, are facing an immense task. Within the next few years, they are going to have to educate an entire Navy in the complicated business of fighting a submarine fleet that can attack from long range and will be able to match surface forces in speed in low sea-states and will be able to out-run them in heavy weather. Make no mistake about it, while individual crews are generally proficient in their own type tactics, the Fleet as a whole is ignorant of co-ordinated inter-type ASW tactics, doc­trines and procedures. The problem is further complicated by the fact that there is no single sensor/weapon combination that has ever or will ever defeat as flexible an instrument of sea power as the true submarine.

It will never be possible for all ASW training to be concentrated in one command. The best that can be done is to provide direction to the commands that will have to carry out the various levels of training. A certain amount of “cross-talk” between the commands must be made mandatory, but direction must be kept simple. Thus, we come to the purpose of this article—a simple thesis, around which can be built a complex system of fighting and defeating submarines, which we might call “The Doctrine of Incremental Reduction.” As the DIR thesis implies, successful ASW can be accomplished only by erosion of each of the submarine’s many capabilities. If the submarine is permitted to use all of her capa­bilities unhindered, we will lose. On the other hand, if we can in some manner endanger the submarine each time she employes one of her more significant capabilities, we can win- even in a war of attrition.

Considering the submarine herself, the characteristics that contribute most to her capabilities are: high speed, deep depth, good

maneuverability, and long endurance. Let us tackle these one at a time. At least for the present, submarines do pay a penalty for the use of high speed, particularly at shallow depth. The faster they go, the more noise they make, noise that is detectable by a wide range of passive sonar/sonobuoy systems that can be carried by aircraft, ships, and submarines. Here is where we can apply our first DIR. We must employ our forces to make the subma­rine risk detection by us each time she uses high speed.

Submarines go to deep depths in most cases in order to evade, to search, or to enable themselves to travel at high speed with a minimum of radiated noise. In going deep, the submarine again pays a penalty. De­prived of atmospheric sensors, she is depend­ent entirely upon sonar, and this sensor is severely limited in many cases by an unfavor­able thermal structure. Her hull is more vul­nerable to damage from any source as she approaches collapse depth. There is less mar­gin for error. She is deprived of the effective use of all but a few special purpose weapons, such as homing torpedos, and the effectiveness of these may be reduced. If given full freedom of movement the submarine will therefore operate in the surface layer most of the time. Two DIRs can be made to apply here. If our mission is to seek out and destroy, we should encourage the submarine to operate in the surface layer where she is more detectable. If we are trying to prevent the submarine from firing weapons, we should force her to remain in deep depth. Happily, in some cases we can do both of these things simultaneously if we have enough forces. For example, we can use pickets and screens placed to detect the sub­marine in areas where she likes to operate near the surface and use pouncers in areas where she would like to shoot.

The ability to change heading, depth, and speed rapidly can also penalize the submarine. The penalty she pays in this case is that she is more easily classified if she is maneuvering radically. The dead-in-the-water target is still harder to detect and classify than a target showing appreciable doppler or a submarine­like track. The next DIR is: make maneuvers by the submarine pay off in better classifica­tion. With dead-in-the-water targets, force the submarine to move whenever possible. Some­times this can only be accomplished with the expenditure of ordnance.

Endurance presents us with one of the toughest problems in ASW today. There is very little we can do to decrease the endurance of the submarine herself. With a range capa­bility of 50,000 miles or more, the submarine can operate for extended periods where there is sufficient depth of water. Perhaps the ma­chine is better than the man. Submarine war patrols can be grueling experiences. They could be made almost unbearable if the sub­marine crew were convinced by some means that they were detectable at extremely long ranges and would be attacked as soon as they became a threat. Our present sonars now have the ability to esonify large areas of the ocean. Newer sonars, using more power, will greatly add to this capability. Also, these sonars are being carried in submarines as well as surface ships. Now put yourself in the position of a submarine commanding officer who has heard low frequency echo ranging for several hours without being able to otherwise detect a target. Is the ping coming from a surface ship

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^at a great distance or could it be coming from a submarine that is close and is about ready to nre torpedos? You could never really be sure, ^and if such a situation continued for days you ^w°uld probably react by becoming less aggres­sive or by ignoring the sound altogether. To accomplish this DIR, we must employ our orces wherever possible in ways that will con- ^v*nce the submarine that she is being watched 'md sooner or later will be attacked.

Now let us examine the sensors that sub­^marines use for detection, classification, and ^a^^ack- Taking the passive sensors first, con- ^{Sl e}r the most vital, sonar. While showing Potential, passive sonar is fairly new in ^s role as the primary detection equipment ^0r submarines. In World War II, the combi- g,^a|*°ⁿ °f radar and visual search was favored, °ugh initial detections were made by ^ar with increasing frequency toward the of the War. Very few attacks were made _a £ ^S°^nar ^formation only for fire control, Yyj_ ^t^^ley were not particularly successful, ly ^cn relying on sonar alone, the submarine’s 'ggest headache is classification. If permitted

she will classify by other means. The subma­rine’s next biggest headache is obtaining a fire control solution, a business that is compli­cated if the target is making high speed and using frequent changes of course and speed. It is also complicated if the noise level in the vicinity of targets is high, making it almost impossible to isolate individual targets. While it will rarely be possible to operate a large group of surface ships quietly, it is certainly possible to operate a single ship at quiet speeds where it can be detectable by passive sonar only at very short ranges. This DIR has two parts: part one, when seeking to avoid long-range detection by passive sonar, op­erate quietly and adopt the best posture to detect periscopes, radar, and active sonar; part two, when unable to operate quietly, employ forces in a manner that will prevent the submarine from getting a fire control solution by passive sonar—by maneuvering, by sonic saturation, or both.

of _a, ^lr*⁸ deep to evade, search, or to travel at high speed, the submarine is deprived an _Unf^OS^”^er*^c sensors and is dependent entirely upon sonar, which is limited by ^sPeed ^aV°^ra^'^e thermal structure. Too, her ability to change heading, depth, and ^rapidly can be used against her, for she becomes easier to detect and classify.

The next detector available to the subma­rine is her electronic intercept equipment, ECM and HF/DF. It is used almost continu-

Commander Holt served in the USS Dragonel (SS-293) during World War II. He was ASW Instructor, Fleet Sonar School, Key West, Florida, from 1950 to 1952, and executive officer of the USS Redfin (SSR-272) from 1952 to 1955. He then served as executive officer in the USS Wallace L. Lind (DD-703) from 1958 to 1959, and as commanding officer of the USS Robert L. Wilson (DD-847) from 1959 until 1961. He is now Head, Trainer Department, ASW Tactical School, Norfolk, Virginia.

ously when the submarine is near the surface and provides a very good classification capa­bility, usually better than sonar or radar. It is the only means the submarine uses for detec­tion of aircraft beyond visual range. It is no wonder that submarine commanding officers outstrip their surface and air counterparts in becoming experts in this field very quickly. Now what can be done about it? In extreme cases, we might stop radiating on all fre­quencies. Most often, this costs too much in terms of our own capabilities and a compro­mise must be reached to deny the submarine the effective use of this very fine piece of equipment. This DIR, then, states that elec­tronic equipments that identify or fingerprint a particular unit or group will only be used on emergencies, and that a balance will be main­tained between detectability by electronic intercept and detectability by other means, primarily passive sonar.

Submarines continue to rely on the peri­scope for their best fire control and classifica­tion information. Too frequently, they use it with complete freedom, even abandon, in cases where it should be detected. Nowadays, the “scope” is apt to be a multi-purpose tool. It can be used to get optical range, radar range, electronic intercepts, and celestial fixes, in addition to getting a look at a ship or an aircraft. Submariners like to use it, and they use it whenever they can. They will take risks to use it if they think it is needed. The risk is that the submarine must operate the periscope from the surface layer where she is usually more detectable and more vulnerable. To deprive the submarine of the effective use of her periscope, the next DIR says that we should station forces with the means to detect her visually, by radar and sonar, in areas where she is most likely to use the periscope for classification or for attack.

All modern submarines are equipped with active sonar, Fathometer, high frequency radio transmitters and radars. Why? Because they need them to assist in the accomplish­ment of their mission. In most cases, these active equipments are used only after passive means have failed. That they are frequently used is in itself an indication of the marginal capability of passive systems. A submarine unable to get an accurate navigational fix by passive means will use the Fathometer if she thinks she can get away with it. If she has vital information to transmit, or thinks she does, she may use HF radio if other means are not available or seem not to be getting results. She will certainly use active sonar and radar on those occasions when she thinks she can do so without altering the target. At the present time, we need additional equip­ment in our ships and aircraft to give us a capability to intercept more of these active transmissions. Most of our submarines already have it or will get it in the near future. This DIR needs a great deal of attention. Develop and deploy passive systems that will severely limit the tactical use of the submarine’s active sensor systems.

The submarine, like any other instrument of sea power, is no better than her weapons and her means of controlling them. Let us take the submarine-laid mine, since it is usually the most difficult weapon to detect. It is also very hard to counter. And as with the subma­rine’s other weapons, the threat alone ties up forces completely out of proportion to the numbers of forces required to impose that threat. But it does not come free of cost. The submarine must pay in reduced loads of other, more popular weapons. She has to penetrate further inshore, where she must surmount increasingly stiffer defenses. The minefield can become reduced in effective­ness, sometimes worthless, if she is detected ir> the vicinity of the mine plant. Accurate navigation becomes a difficult problem. Fre­quent use of the periscope may be needed, perhaps even radar and the Fathometer- Also, it is a very noisy business in most cases- And the submarine is never sure that the

enemy has not beaten her to the punch and planted their field first. Even seeing surface ships in the vicinity is no assurance that there is not an antisubmarine field there. The applicable here states that the best chance of early detection of a submarine-laid nainefield is to catch the submarine in the ^act hy developing detection systems that take advantage of his increased detectability ^Vvhen laying a field, and to use our own mines ^t0 discourage this practice where possible.

f he traditional weapon of the submarine ^ls the torpedo. Within the next few years, the torpedo could be replaced by some type of ttiissile, but for the present, the torpedo is ¹ the best weapon for use by submarines Against ships. The type of warhead, high ex- osive or nuclear, will be determined by ^ ^e type of target. While the nuclear war- o goes a long way toward simplifying fire rol problems, it is too expensive to use ^gainst non-vital targets. Whatever the type ^Warhead, the submarine is more detectable lik ^       ^a spread of torpedoes than she is

y to be at any other time, and also more ,/^ble. While not altogether manda- y. a submarine commanding officer would on"" ^{prep;r to} f^lre his fish from a boat that is Wat* ^Steady course at a slow speed in shallow his ^Cr posture permits him the full use of cla ^Pff‘^sc°P^e for obtaining fire control and Part ^Cafi°ⁿ information. The further he de- tiv ^S ^^r°^m this posture, the more his effec- here*^^SS *^{S reduced}- The corresponding DIR surf ^{IS t0} fitree the submarine to abandon the sul ^a.^{Ce layer w}hen she shoots torpedoes and to her to quick long-range attack if she b_es|^a*^ns ,*ⁿ the surface layer to shoot. The _stjjj ,^^Vlce for forcing the sub to go deep is i ^ae employment of explosive ordnance ^er general vicinity.

^e>dst ^{SSl e}"fi^r^ⁿg submarines have been in Wer_e^Gc^Ce ^^{or more} than ten years. While they We *^{lrst ern}ployed to threaten fixed targets, r_n^{arc n}°w entering an era where the sub- for'--^nC^"Punched missile is a threat to mobile

W₀.'i’^S, ^{at sea}- To be effective, such a weapon ity h^ave some terminal guidance capabil- _c]ea^and the payload would have to be a nu- th_e ,^Warhead. Presuming this to be the case, hefo_r^ances detecting the firing submarine ^re she launches such a missile is doubtful

in most cases. The best defense appears to be a system of countering the missile before it can cause significant damage. The DIR for this problem must be accomplished in three steps: use nuclear spacing for surface forma­tions; deploy AAW forces for close-in protec­tion from all sectors; and deploy ASW forces, particularly aircraft, to give a reasonable de­gree of surveillance over the most likely launch areas. Since even a submerged missile launch is detectable at long ranges, these aircraft would have a good chance of killing the launcher if equipped with an appropriate stand-off weapon.

Admiral William S. Sims was speaking with convoys in mind in 1918 when he said that offensive ASW meant forcing the enemy submarines to play on your terms on ground of your own choice. With our growing capa­bilities to predict environmental conditions at sea, it is now possible to choose our own ground in most phases of ASW. In those few cases where this is not possible, we can at least be warned of unfavorable conditions and can modify our plans to accommodate the reduction in our capabilities. In addition to environmental forecasting, there will be other intelligence available concerning the probable locations of submarines. Positions of sightings, sinkings, electronic intercepts, passive sonar and sonobuoy detections will all serve to give indications of low density routes that can be profitably employed. The final DIR belongs to Admiral Sims, “Make the submarines fight on your terms on your own ground.”

Whatever his rank, any officer assigned to ASW duties is continually faced with a long list of rapidly changing conditions that must be understood in intimate detail before he can do his job properly. It is no longer enough that he have only a good apprecia­tion of his own ship, aircraft, submarine or shore installation. He must know the capa­bilities of all of them when used separately or together, in any combination. He has got to know what a submarine can and cannot do and what it is most likely to do. And some­one is going to have to teach this doctrine to most of the officers and men in the Navy if we are ever to be able to counter a growing submarine threat to the freedom of the seas.