Chapter III

Section 1
Tasks
General Considerations

3101. The following expression of doctrine for all tasks covered pre-supposes:

      1. That it may be modified by the issue of orders.

      2. That it may be materially affected by varying and unanticipated conditions.

      3. That all commanding officers appreciate the importance of information of the enemy and exchange of information relative to own operations, and that the making of contact reports, whenever possible, will be automatic.

      4. That all commanding officers will be thoroughly acquainted with their mission in each situation and will, therefore, realize that a course of action which will further the accomplishment of one mission may not be the proper one under different circumstances.

      5. That the importance of accurate navigation is obvious and that contact reference points used will be those most likely to locate the enemy.

      6. That all concerned are familiar with the limitations of submerged operations, both in time and in area covered.

3102. Commanding officers must realize that the nature of submarine tactical operations places upon them greater responsibility and presents to them greater opportunity for exercise of initiative than is accorded commanding officers of other types; and that the responsibility for maintaining touch with their immediate or other designated tactical superior is correspondingly increased.

3103. The nature of submarine operations is such that a submarine commander will be confronted frequently with the necessity of choosing between offensive and defensive tactics. His action may be a compromise as circumstances seem to dictate, but upon his decision will depend largely his success in damaging the enemy and in preserving his own ship. In other words, he must weigh the probable damage resulting to the enemy against the probable risk to his own vessel. If there is a reasonable chance of inflicting serious damage to the enemy, duty requires that extreme risks be taken. On the other hand it would be folly to hazard ship and crews in an attack upon an unimportant enemy vessel whose destruction could little affect the issue. Prompt and correct decision in such cases can be attained only by self-training carried to the point of making decisions and action a simple part of the day's work.

3104. Particular consideration must be given to communications. Important information and directives will be passed to submarines on prearranged radio schedules.

Section 2
Procedure When Operating in Connection With Fleet Dispositions

3201. The accepted doctrine that submarine operations may be coordinated with, but not closely combined with those of surface craft, is the primary reason why no positions are prescribed for submarines in fleet approach, contact, and battle disposition. The duties and operations of submarines in connection with the destruction of enemy heavy ships are the same whether they are operating with the fleet or organized as independent units. When operating with other organizations in war, the duties of submarines must include the observance of certain precautions that are necessary in order to avoid being treated as hostile by own forces. At sea, submarines avoid passing through own fleet dispositions, surface or submerged. If through breakdown or casualty, passage on the surface through own fleet cannot be avoided, the submarine should be escorted by a surface vessel and all task forces promptly informed. Even though in proper position or on assigned stations, submarines must be alert to the possibility that own surface vessels, aircraft and submarines may mistake their identity. If on the surface when units of own fleet are sighted under circumstances where visual recognition methods may not be effective within sufficient time, submergence is resorted to in order to avoid detection by them. When submerged, identification, if necessary and warranted by the circumstances, may be established by the use of underwater sound equipment or by recognition signals from the submerged signal gun. It may be expected that a submarine will never emerge in the vicinity of friendly surface craft except in an emergency, without first establishing its identity.

3202. When the fleet is in the approach disposition, submarines organized as a task group shall maneuver to reach favorable attack position undetected, at which time the doctrine for coordinated attack becomes effective. In order to orient position to take care of changing situations, submarines will remain on the surface, if practicable, until contact is made. During fleet approach formations, the submarine unit will usually be disposed well in the van of own main body, probably in a scouting line formation dependent upon information of the enemy fleet. If movements of the enemy have been determined sufficiently well for the submarine unit commander to plan a coordinated attack, the submarine unit will be maintained in a compact formation to provide for rapid communications. Deployment of submarine unit will be made as early as practicable, but it may be anticipated that absence of information will necessitate that deployment be accomplished only a short time before actual contact, necessitating the use of maximum surface speed in attaining position. The success or failure of submarines to reach favorable attack position during fleet approach may depend on whether or not enemy aircraft are encountered. A single plane sighted (friendly or hostile) will normally be sufficient cause for a submarine to avoid detection by submerging. Under the conditions of imminence of contact with the enemy main body, this will be influenced not so much by the vulnerability of submarines to air attack as by the loss of their primary asset, the surprise element. If their presence and position becomes known, enemy forces may be maneuvered to avoid contact. To overcome aircraft interference with the submarine surface approach, an escorting force of surface or aircraft, or a combination may be successfully employed under some circumstances. In order to effect an advance, taking full advantage of available surface speed, submarines may cruise with own battle line during daylight, breaking off during darkness to gain attack positions ahead.

3203. There are no prescribed positions for submarines in fleet contact dispositions. By this time they have already concluded their attack or have abandoned it, and by doctrine, will have started trailing or taking up positions which may permit attack during the enemy's retirement. Contact scouting by submarines, if opportunities for such are presented, during approach and contact dispositions may be of tremendous value to the O.T.C.

3204. There are no prescribed positions for submarines in fleet battle dispositions unless, under special circumstances, they are previously disposed for use as an anvil. If the submarine attack has not been executed before the battle starts, submarines should seek

positions ahead of the enemy battle line or in areas through which the enemy may be expected to pass. Otherwise, they should trail the enemy battle line in order to take advantage of any favorable change of course or to complete the destruction of disabled enemy heavy ships. If they find themselves in the immediate vicinity of a night engagement, the correct procedure for submarines is to resort to deep submergence.
3205. For tactical formation and the attack doctrine, see Chapter IV, section 10.

Section 3
Patrol

3301. Patrol operations may be ordered to accomplish one or more of the following missions:

      1. To attack enemy lines of communication in a particular area or along a particular route or line.

      2. To blockade an enemy coastline.

      3. To establish control of a sea area.

      4. To protect a fleet in an exposed anchorage.

      5. To conduct an observation patrol.

3302. Ordinarily, patrol will involve offensive action. Depending, of course, on the area to be covered, the disposition of submarines should be such as to permit as many as possible to deliver attacks. In some situations, a coordinated attack plan may be desirable.

3303. Because of the difficulty of two-way identification, friendly surface vessels and aircraft ordinarily should not be assigned to patrol the same area with submarines.

3304. Patrol against enemy lines of communication includes the destruction of commerce. It may be expected that the convoy system will be used, especially at focal and terminal points. On the high seas, circuitous routing will be employed. The torpedo is the major weapon in these operations, as the submarine is not equipped with gun power to equal that which may be expected on modern merchantmen. The submarine gun may be employed against vessels known to be unarmed or small vessels of minor resistant qualities. Operations in the vicinity of focal and terminal points will produce more targets, but the intensity of anti-submarine measures will also be increased. The principles of the submarine attack against commerce do not differ from those used against other types of vessels. Submarines operate singly in assigned sectors on the edge of focal and terminal areas and furnish information of enemy shipping to other submarines similarly employed. Submarine positions should be shifted frequently to cover variations in shipping routes as well as to evade concentrated anti-submarine effort in areas of operations discovered by the enemy.

3305. Operations in opposition to a joint overseas advance:

      1. In opposing an overseas advance, submarines may be employed profitably in attrition operations against the enemy force during passage and in attacks at or near its destination. The physical objectives may be either combatant ships or auxiliaries. Of the latter, transports are especially valuable targets.

      2. In such activities, submarines may work entirely unsupported, but their value will be increased if supplied with information by other forces or if the operations of other forces are coordinated with those of submarines.

      3. Submarines operating unsupported or unassisted by other forces will have to locate the enemy first, then obtain positions ahead, concentrate, and attack. Search patrol, or observation is required for the first phase. This usually can be done best near the probable destination of the enemy because of the reduced area to be covered. However, the ideal method is to trail the enemy from his point of departure, and, from information supplied by trailing submarines, concentrate attack groups ahead along his assumed course.

      4. A very probable type of combined operation will consist of cooperation between patrol planes and submarines, the former furnishing information upon which the latter may proceed to attack positions. The doctrine for such a combined operation is contained in Submarine and Patrol Plane Inter Type Tactical Bulletin.

Section 4
Scouting

3401. The object of all submarine scouting operations is to gain information of the enemy and transmit such information to the O.T.C. with the utmost dispatch.

3402. Since they are able to operate unsupported by other forces, submarines are valuable scouts in distant waters or in waters which are under enemy control. However, in waters patrolled by enemy submarines, or when within range of enemy planes, submarine scouts must remain submerged for protection during daylight. When restricted by such conditions, the area covered by each submarine scout is necessarily small, and communication except during darkness is limited to that obtainable with the vertical antenna, which has an effective range of about 100 miles. When on the surface, radio communication range of submarine is comparable with that of surface vessels.

3403. The scouting distance for submarines on the surface should be not greater than 20 miles and that for submarine submerged should be not greater than 12 miles. It is highly probable that submarines will have to conduct a submerged patrol during daylight hours unless own forces have control of the air.

3404. Unless otherwise ordered, submarines engaged in scouting operations communicate as directed in Article 3104. A relay vessel will be stationed in rear of the submarine scouting line when circumstances warrant.

3405. If possible, contact with enemy surface forces should be maintained until the mission is accomplished or until ordered otherwise.

3406. Formation, deployment, and maneuvers of the submarine scouting line will be conducted in accordance with the General Signal book, and this Doctrine.

Section 5
Screening

3501. Submarines that can maintain fleet speeds may on occasions be employed for distant screening operations, the object of which is to protect the screened force by warning of approaching enemy forces and by offensive operations against them. Enemy air activity will serve to minimize the possibility of this type of employment.

Section 6
Mining

3601. The operations of a submarine mine layer are entirely defensive if only mines are carried. The submarine may be assigned to observation tasks or to offensive roles, if provided with torpedoes in addition to mines.

3602. Mining operations may be classed as tactical or strategical. Tactical mining consists of laying mines in the presence of the enemy, as in planting mines across the entrance of a harbor in which the enemy is located. Strategical mining consists of planting mines in areas not at the time occupied by the enemy, but in which he is expected to operate at some future time. If surface mine layers are available, they should be used for strategical mining where practicable and submarine mine layers should be conserved primarily for tactical mining.

3603. In the case of mining, accurate navigation is especially important in order that mines may be planted in the exact location desired.

3604. 1. Submarine mines should be planted with the following considerations in mind:

         1. A mine plant should consist of more than one field.

         2. Each field should contain a different number of mines.

         3. Mines in each field should be planted at irregular intervals.

         4. Mines should not be planted in a continuous line.

      2. The extent of any one mine field should be limited to 10 or 12 mines, unless conditions make a larger field imperative.

      3. Mine plants in shallow water of from 100 to 150 feet should be made during darkness to prevent discovery by aircraft. Plants made in depths over 150 feet can be made at any time as observation by aircraft at such depths is extremely unlikely.

Section 7
Reconnaissance

3701. Observation and reconnoitering are special forms of scouting confined to specific areas. Bearing in mind the value of negative information, the object is the same as in all other scouting operations; namely, to gain information of the enemy without being detected. The submarine is especially valuable for these purposes because of its ability to remain unsupported for long periods in waters under enemy control.

3702. Submarines are capable of performing three the following[*] types of reconnaissance missions:

      1. Visual reconnaissance through the periscope.

      2. Photographic reconnaissance through the periscope.

      3. Reconnaissance by landing party.

      4. Radar frequency reconnaissance by search receivers.[*]

3703. The object of reconnaissance is to obtain all possible information concerning the locality under observation. This includes weather, navigational and hydrographic information, terrain, quantity and quality of defense installations, numbers and disposition of troops, or other specific information requested.

      1. Periscope visual reconnaissance can be conducted at any time during daylight unless strong anti-submarine measures are encountered. The report of the reconnaissance should include a complete description of all important items observed and panoramic sketches of the locality showing the location of the major points of interest.

      2. Periscope photographic reconnaissance is employed to supplement visual reconnaissance and to supply better information on the locality than can be shown on panoramic sketches. In addition, it is oftentimes possible to pick out items on a photograph that are invisible to the eye. Submarines will develop the photographs and supply immediately a fair interpretation of important objects that stand out in the photographs. For a complete and comprehensive interpretation of the photographs, they should be delivered to a regularly established photographic interpretation unit.

      3. Landing party reconnaissance will be conducted at night by men sent ashore in rubber boats. These boats come in several sizes and hold from four to twelve men. They are charged with CO₂, propelled by outboard motors or paddles, and constructed of tough fabric that will not tear when driven over coral reefs or rocky ledges. The submarine should approach the landing area as closely as possible, completely darkened and with minimum noise. If it is planned to anchor to await return of the landing party, the anchor should be backed out and arrangements made for slipping the cable if necessary. The landing party may be sent ashore and retrieved the same night or on the following night. The success of landing parties depends largely upon the care with which communications with them from the submarine are arranged. The use of visual signalling, even though blinker tubes are employed, is extremely hazardous except in very isolated areas. Underwater communication gives the best prospect of success. The landing party can be equipped with stethescopes to be placed in the water for listening and with a simple portable electrical transmitting device or with a bell and hammer. A comprehensive plan with all details carefully worked out and with alternative procedures specified should be made up for every landing operation.

      4. Radar frequency reconnaissance, by the use of special receivers and associated equipment, can be conducted for determining the presence of radar stations installed on enemy bases, ships and air-craft. This same equipment can be used as an early warning device, warning of the presence of radar search by the enemy, due to its great range.
         RPM 1866.[*]

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* Text in green represents a "pen and ink" interim change.

Section 8
Services to Aircraft

3801. Certain fleet submarines, in which modifications to ballast tanks have been made, are capable of carrying gasoline, lubricating oil, and minor supplies for aircraft. Planes can be fueled underway in the open sea under favorable conditions as well as in protected roadsteads. A squadron of patrol planes can be serviced rapidly and efficiently. Thus, submarines may be used to support seaplane flights to and from outlying points where surface tenders are not available or cannot be maintained. Information as to what submarines are equipped for this service, together with their characteristics, can be obtained from the submarine command.

Section 9
Lifeguard Missions

3901. A new mission brought on by the present war is that known as "lifeguard duty". The main purpose of this mission is the rescue of downed aviators in the vicinity of some enemy position, which has been bombed by a friendly task force. In addition, when inclement weather is encountered in the vicinity of the target, the submarine may also be used as an aid to aircraft navigation.

3902. Important points that will aid any submarine assigned to such a mission are given, as follows:

      1. Submarine should ascertain the nature of the mission, the force involved and its disposition.

      2. Complete and thorough study of the entire operation should be made. Provisions should also be made in case any change or extension of the Operation Order is effected.

      3. The voice transmitter set, to be used with aircraft, should be carefully tested and checked prior to departure.

      4. Be prepared to furnish accurate navigational information in a simple, abbreviated form to flights of planes during inclement weather.

      5. The best searching speed is about 15 knots. However, if numerous white caps are present the speed should be reduced sufficiently to permit the lookouts to cover their areas carefully, since it is difficult to pick up a small yellow raft against a white cap background.

      6. A successful method of searching that was used by a submarine recently assigned this type of mission which resulted in the picking up of six aviators is presented. This method is known as the spiral-rectangle method, with the long axis along the extended set.
         
         NOTE--The distance between successive legs of the spiral should be reduced to two miles in rough weather.

      7. It is difficult to determine the nationality of a pilot who is wearing a helmet. Therefore, before approaching too close, make the pilot remove his helmet for identification purposes. This may save your personnel from being shot.

      8. Remember that life rafts drift faster than submarines when approaching them for recovery. Also, excess backing power will wash the life raft away from the submarine.

      9. The rescue party should be kept to a minimum and usually not more than three men are required for recovery. One of the handiest pieces of recovery equipment is a life ring securing to a heaving line.

      10. Be sure Pharmacist's Mate knows how to treat "immersion foot" or "immersion leg" in accordance with latest medical instructions. Red Cross survivor kits should be carried as they are extremely useful in cases of rescued pilots.

11. During night search do not under estimate the distance to a Very's Star. Stars which appear to be three or four miles away have been found to be actually eighteen or twenty miles away. A whistle blown through the megaphone from bow to bow during night cruising may be of assistance in awaking a pilot on a raft and, thus, allow him to fire a signal light.
1. It must be remembered that even though our air groups are striking enemy air bases, the enemy will undoubtedly have some aircraft available and will attempt to strafe or bomb submarines employed in this type of mission. Therefore, all lookouts must be particularly alert during this type of work.

2. Friendly aircraft will be employed as a screen for submarines on lifeguard duty whenever possible.

3. When a report of a downed aviator is received, the submarine must exert all within its power and endurance to continue the search until ordered otherwise.

4. A good average to use for drift is 4% of the wind velocity when calculating possible positions of downed aviators.

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