How to hunt a submarine – To Catch a Thief, Send a Thief

To catch a thief, send a thief

Every once in a while, I think about submarine related questions. One of those questions is what is the greatest danger to submarines?

I think the question could have many answers based on the circumstances. The sea itself is certainly a big challenge. Even in the calmest conditions, the sea is an unstable mass that provides both the opportunities for a well-built submarine and the greatest challenge. History is filled with submarines being rammed on the surface in relatively calm waters because of their low silhouette and visibility.

The list goes on and on and includes weather, other ships and submarines, airplanes and helicopters, and so forth.

But it occurs to me that in the hundred plus years the modern submarine force has existed as a part of the US Navy, one of the greatest dangers is peace. Don’t get me wrong. I like peace. I served during several periods of conflict and the stress and tempo are very hard on the boat and the crew. But the peace which typically follows conflict is always one of the greatest threats to the submarine fleet in general.

The big example was the aftermath of World War 1. The carnage caused by those highly effective primitive boats was a stunning blow to both the British and American leaders. All that money spent on giant battleships and dreadnaughts was nearly swept aside by tiny vessels with a basic point and shoot weapon that had no countermeasure. The merchant ships that were so vital to the survival of all the warring parties were easy targets for the U-boat captains.

So in the aftermath when peace treaties were being discussed, the existence of submarines were called into question. The Admiralty lobbied with great ferocity in the halls of government and the loyal press to damn the torpedoes and the boats that carried them once and for all. It was only the tenacity of the American Navy and some visionary men in Congress that prevented the abolition form taking place. Only time would have told if that abolition would have been truly adhered to but the progress made by America between the wars would have been even more greatly hampered.

The success of submarines on all sides was a hallmark of World War 2. But when the war was over, well intentioned politicians and people who were weary of war once again sought to bridle the horses. To be fair, in the late 1940’s, there was even an attempt to create a single Department of Defense Force with no division between the services. After all, we had the bomb and the old ways of war were going to be obsolete once more. Or were they?

The Soviets had captured the remnants of large portions of the German Navy and their engineers. Their quick expansion into previously held territories that had sea ports ensured that their Navy could grow into a global power. And they had already been able to see the power of missiles launched form submarines from a great distance.

Both sides were racing to develop missile technology and submarine propulsion that would extend the impact of submarines.

It is fortunate that the American Submariner Community never gave up the vision of why submarines would be a part of the potential conflicts to come. This article is about the strengths, weaknesses, opportunities and threats that submariners faced in 1951.


Submarine Development Group TWO

Declassified to Unclass April 13 1967

Presented at the Sixth Undersea Symposium

9-10 May 1951 Washington, D. C.

This document contains information affecting the national defense of the United States within the meaning of the Espionage Act, U.S.C. 50, – – 31 and 38, as amended. Its transmission or the revelation of its contents in any manner to an unauthorized person is prohibited by law.

185 SERIAL NRC:CUW:O119            Copy No. 185

In an interview for a national magazine a few months ago on the subject “Why all three services are needed”, the Chief of Naval Operations, Admiral Sherman, was asked a question as follows:

“Last year was not the whole fleet sunk in maneuvers by theoretical enemy submarines in spite of the best equipment developed?”

The Admiral’s answer in part was, and I quote, “No, however, if a submariner did not believe that submarines were capable of sinking a whole enemy fleet, he would not be as enthusiastic as he should be. It is a mistake to accept zeal and enthusiasm as completely factual.”

In my remarks before this Sixth Undersea Warfare Symposium, if I should, by chance, offend a particular branch of the United Anti-Submarine Forces or appear over confident or boastful, please bear in mind that I am a submariner full of enthusiasm and zeal for any task assigned a submarine, especially submarine versus submarine.

A year ago, the Hartwell committee challenged us as to the submarine’s place in antisubmarine warfare. To a submariner, that is like asking an aviator what is the place of aircraft in anti-aircraft warfare. A sub mariner looks upon a fighter submarine or an SSK in the same light as an aviator views a fighter plane. Undersea warfare is primarily submarine warfare and the submariner feels that he plays an important role in this stratum.

To further emphasize to this Symposium how an enthusiastic and zealous submariner looks at the picture from his pro-submarine viewpoint, here is an imaginary situation:

Suppose I were an enemy submariner today and in command of a submarine equivalent to a U. S. fleet or Guppy type. Further, suppose war started today and I was ordered out to sea with a mission to sink U. S. shipping.

Further, suppose I knew today’s capabilities of U. S. ASW forces. With these assumptions – what would cause me the greatest worry and constant mental strain? It would be the U. S. submarine. Particularly would this be true from the time I left port while I made transit to my target area and again in transit from my target area back to port.

A submariner feels confident that he will detect the presence of surface craft or aircraft before they detect him or at least he will be aware of them before they have launched an attack. Mental stress placed upon the submariner by these agencies are of a temporary nature as the occasion arises. But, the invisible, non-detectable enemy submarine constitutes a constant and continual menace, real or imagined.

Submarine Development Group TWO is based at New London, Connecticut. She consists of two Guppies and two fleet type submarines and a small staff operating as a unit under Commander Submarine Force, U. S. Atlantic Fleet. Her specific assigned mission is necessarily cannibalistic to a submariner. It is to solve the problem of detecting and destroying an enemy submarine by means of a submarine. While we are enthusiastic and zealous, we must be completely factual in our reports.

As submariners, we do not view such a mission as something new, for it can be done and has been done. Of course, what we are really trying to do is to improve the probability and capabilities of our submarines to detect and destroy enemy submarines. If we should ever succeed in carrying out our mission, namely solving that problem it would mean the end of undersea symposiums. However, such a mission is most proper, for it enables us to repel boarders and concentrate on first things first, and only those things that aid a submarine to detect and destroy another submarine.

The primary mission of U. S. submarines in the past has always been to sink surface ships. Our operations and tactics were designed to fully exploit this assignment by taking into consideration the caliber of the enemy opposition. It permitted considerable surface running to both search and gain attack positions and even permitted surface attack. The capabilities of our submarines to use their greatest single tactical characteristic, that of submerged invisibility, has never been fully exploited by U. S. Submarines in combat. It is that ability to get there, stay there, remain undetected as long as desired, and disclose her presence only by the launching of an attack.

Present day submarines sacrifice or reduce their primary military characteristic in varying degrees whenever they operate on the surface, snorkel, use radar, expose periscopes, transmit on radio or proceed at high speeds near the surface. To help preserve her primary characteristic, she transits on snorkel, fully utilizing RCM, operates completely submerged in her areas, charging on snorkel for short periods, restricts periscope exposures and maintains radio silence. Her search is thus greatly restricted. To be effective she must be stationed in a productive area.

This type of submarine operation will be a must for our enemy. It is also a must for our fighter submarines. The enemy’s problem is different from ours in this respect: He must sacrifice his primary characteristic of invisibility to get from his bases to his operating or target areas. He must make speed and proceed part of the time on surface or snorkel. He may be protected in this transit by his own planes or sur face ships, but in these transit areas, he is subject to attack by our submarines. These are the areas where we will hunt him, areas in which it will not be reasonably profitable to operate our other ASW forces, namely planes or surface ships because of the enemy opposition.

When a submarine attempts to operate like a true submarine, preserving her invisibility, she finds herself extremely limited. The periscope is limited by visibility and mathematically by its height out of water and the target’s height above the surface. RCM is limited by the enemy’s operations. Radar is limited by the atmosphere and approximate line of sight. Passive listening sonar becomes the all-important detection, tracking, and approach tool for, above all others, it permits the primary characteristic of a submarine, invisibility, to be preserved. Even today for a certain percentage of time, passive listening sonar will out-range periscope or radar for detection purposes.

I have said that we put first things first. The first part of our directive in our mission was to detect. With present equipment, we are in effect searching sonar wise with an 8000 yard yard-stick. Sometimes, depending on conditions, it is 20 to 30,000 yards and sometimes it is 2 to 4,000 yards. But the average is about 8,000. Our limitation as an effective ASW tactical weapon is our limiting passive sonar detection range. Consequently, my Group has put an accent on this particular phase of the whole problem.

Submarine Development Group TWO is not a scientific or a technical laboratory, nor a production agency. It was logical that as an operating agency we combine efforts with the other agencies in the solution of this problem. It takes us all, just as it will take all forces to solve the ASW problem. No one will have the complete answer.

In cooperation with Underwater Sound Laboratory, New London, Woods Hole Oceanographic Institution, Lamont Laboratory, Columbia and the U. S. Navy Sofar Station in Bermuda, a series of tests were begun about a year ago to investigate low frequency detection of submarines. It seemed very appropriate that the first step in this regard was to check what we call a submarine’s signature. That is, what noise in what frequencies does a submarine make under various conditions of operations, such as surfaced on engines, snorkeling and submerged on battery. The technique of a signature was simple. The background or sea ambient noise level of the ocean was measured in an area with no ships present. The measurements were taken using very narrow frequency bands and covering a range from 25 cycles to 5000 cycles per second. A submarine in a specified condition then entered the area and the measurements were repeated.

The results in detail of these experiments were presented in a paper by Commander Sherry of Submarine Development Group TWO, two days ago at the Third U. S. Navy Underwater Acoustical Symposium. They are also recorded in the 7th through 11th Partial Reports of Submarine Development Group TWO.

If we are to reach out in range with passive listening, there can be no doubt that low frequency listening offers the promise of success. The signatures show:

      • That submarines are relatively rich producers of low frequency noise.
      • That while cruising on engines or snorkeling there are narrow bands in which the level is significantly above the level of nearby frequencies.
      • That narrow band peaks are caused and related to engine explosion frequency.
      • That significantly increased holding or detection ranges are possible by utilizing narrow band low frequency listening.

A submarine operating in what we call the ULTRA QUIET condition, which – in effect is hovering or at very slow speed with practically all auxiliaries off, becomes a sonar platform to exploit to the fullest the low frequency listening techniques. There remains the difficult problem, the development of equipment suitable for use on board submarines. Fortunately for us all, this program is currently underway with appropriate priority. Bell Telephone Laboratories and Underwater Sound Laboratory have the ball and are carrying it down the field.

Submarine Development Group TWO stands ready to assist in operation al tests of whatever nature that will further the development of low frequency listening equipment. We need first the warning that someone is in the area, then if necessary, we will settle for even an approximate bearing, i.e., some bit of operational intelligence that we now lack. If directivity can also be accomplished, we are that much better off.

In short, we wish to use low frequency to:

(a) Alert us, and (b) to enable us to close to a possible intercept position.

We will then use higher frequency passive listening, of the order of our present JT sonar with its bearing accuracy to complete the approach and attack.

After improved detection, the other most pressing problems for submarine ASW are:

  • Improved weapons, namely torpedoes.
  • Improved submerged navigation. This is a must to fully utilize intelligence, to permit possible group operation and to enable us to increase the density of fighter submarines in an area. To me, non-jammable underwater Loran offers the most promise. Naval Electronics Laboratory, San Diego has this project.
  • Finally, we need a means of secure communications from submarine to submarine and from submarine to base. Such development, coupled with navigation improvement means submarine group operations and the ability to take advantage of operational intelligence.

In concluding, I desire to emphasize that the rate of progress in antisubmarine warfare depends upon the combined cooperation of all agencies and operating forces. A symposium such as this to inter-mingle the thoughts, make reports of progress and acquaint each other with the problems is essential to progress.

Submarine Development Group TWO looks forward to development of low frequency listening with confidence and with confidence we will continue to work on a myriad of problems under the major one to solve the problem of detecting and destroying another submarine by means of a submarine. The submarine will take her place along with strategic bombing, hunter killer groups, convoy escorts, ASW planes, helicopters, mine fields, and all the rest of submarine eliminators. It takes a whale of an effort to lick a submarine and while we look into every angle, don’t forget to send a thief to catch a thief.

It is interesting for me to see the questions raised in this article versus the personal knowledge of submarines that I gained during my years on the boats that followed this age. I can only imagine the improvements in technology that have continued to grow since the last time I rode a submarine. I hope someday that someone finds this article and can add to it.

For now, I am content that all of the questions that were raised in 1951 were answered with a pretty high level of achievement for our day.

Like most people, I pray for peace. But mankind just doesn’t have a very good track record of keeping that peace. Until then, I hope we continue to build the very best submarines possible.

Mister Mac

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