War Instructions United States Navy 1944
Chapter 9. Employment of Submarines
Section I. Submarine Characteristics
901. Habitability on the surface and submerged is generally fair under all conditions of extensive operations, if submarines are equipped with air-conditioning apparatus. Although this equipment greatly improves the ship's habitability, oil fumes and battery gases cannot be disposed of when submerged.
902. The principal weapon of the submarine is the torpedo of 30-45 knots speed, with ranges of about 9,000-4,500 yards respectively. Both air-driven and electrical-driven torpedoes are used, the latter showing no wake. Chemically driven torpedoes, which are wakeless, may be developed.
Section II. Submarine Tactics
906. Submarines unsupported, or acting in conjunction with air reconnaissance, can deliver night surface attacks. To attain position for such attacks they may lie in wait in the path of the enemy, or may trail during daylight and proceed to an advanced position during the early dark hours.
907. When conditions permit and the choice is open to the submarine, its attack will be made:
- With wind and sea astern.
- From the direction of the sun.
- From the side away from the moon.
- With the target silhouetted against rising or setting sun.
- From the side least protected by screening ships.
- In reduced or spotty visibility from the dark side.
908. The most favorable position for firing with respect to bearing is from 70° to 110° relative to the target's course. However, the low submerged speed of the submarine limits its commander severely in the choice of approach bearings.
909. The ability of a submarine to submerge enables it to deliver surprise torpedo attacks at close range, to lay mines in waters controlled by or under observation of the enemy, and to obtain
information of the enemy under conditions which preclude scouting by other types. The small silhouette of an awash submarine is very difficult to see at night, and affords the submarine an advantage for night surface attacks.
910. The most serious limitations of the submarine are its vulnerability and medium speed on the surface and its short radius of action and slow speed submerged. The latter factors are coupled with the necessity of recharging batteries on the surface when the limits of submerged endurance have been reached.
911. Secrecy and surprise constitute the essence of successful submarine warfare. Any projected submarine operations which do not provide these elements, which do not contemplate utilizing the advantages accruing from the ability to submerge, and which fail to take into account the inherent limitations of the type, constitute a sacrifice of the potential military value of this weapon.
Section III. Doctrine of General Employment
913. On occasion the mission of the submarine may be such that the successful accomplishment of its task would be jeopardized by indiscriminate attacks. On such occasion the orders to the submarines must clearly state the circumstances under which they are to refrain from attacking.
914. Submarines are also employed for scouting, screening, attacks on enemy lines of communications, mining, and services to aircraft, including rescue of personnel. Other tasks may include delivery of supplies to blockaded ports, delivery of important communications, cable cutting the landing and recovery of spies and demolition or raiding parties in enemy territory, and acting as beacons to guide attack forces to beaches, channels, or bombardment areas.
915. Even the occasional appearance of submarines in widely separated areas serves a useful purpose in requiring the enemy to take defensive measures out of all proportion to the submarine effort. The establishment of convoy systems and the adoption of circuitous shipping routes with their consequential reduction in the service of supply, the diversion of combatant forces to the defense of shipping, the dispersion of forces and the restrictions imposed on the free movements of combatant forces to the defense of shipping, the dispersion of forces and the restrictions imposed on the free movements of combatant units, are all forced upon the enemy by the skillful and judicious use of even a few submarines.
Operations Against Enemy Lines of Communication
919. In operations of this nature the concentration of submarine activities in the vicinity of focal and terminal points results in greater damage to the enemy, although the submarines themselves are subjected to intensified antisubmarine measures. Their positions are frequently shifted to cover variations in shipping routes and to evade enemy counter-action.
920. Submarines operating in enemy waters are not required to transmit reports by radio, except on special occasions where the importance of the communication to be transmitted justifies the disclosure of its position, or on occasions when it is desired to attempt to harass or mislead the enemy by transmissions.
Services to Aircraft
Employment of Submarines in Antisubmarine Warfare
Operations of Attrition
line of his advance. When the enemy's speed is relatively high or when he has the choice of several divergent routes it is best to concentrate our submarines in the vicinity of his known destination, as otherwise he may be able to avoid the areas in which they are disposed. This is especially true in cases where slow submarines only are available. Operations of attrition may be conducted under circumstances in which the destruction of enemy auxiliaries or transports is temporarily of greater moment than the destruction of his combatant ships.
Section IV. Submarine Operations in Conjunction With Other Types
926. A very profitable form of coordinated operations consists of cooperation between aircraft and submarines, the former supplying information upon which the submarines may proceed to positions favorable for attack.
927. In joint submarine and aircraft operations, except when specifically called for in prearranged plans, aircraft normally avoid areas known to be occupied by own submarines, do not approach submarines known to be friendly and avoid maneuvers which could be construed as attacks. Submarines are required to initiate identification procedure on sighting friendly aircraft.
928. Whenever submarines are operating with other forces all ships and aircraft must be informed of the location and probable operations of these submarines. This includes submarine operations ahead of our own forces, on scouting lines, in the enemy's probable track, and off bases or objectives.
929. Aircraft must be kept fully informed of submarine operations when submarines act in conjunction with aircraft. Submarines proceed to and from their stations in definitely specified lanes which they will enter at pre-established times. During at least part of their surface runs, especially when within range of shore defenses they are escorted by surface ships.
930. In the vicinity of our bases an area designated as a submarine sanctuary is established in which submarines will be free from attack during specified periods. When friendly submarines which have been submerged in the vicinity of the base desire to surface they do so within the limits of the sanctuary and identify themselves before proceeding out of it.
931. No positions for submarines are normally prescribed in approach, contact and battle dispositions as, in general, submarines operations are coordinated, but not closely combined with those of surface craft composing such dispositions.
932. In anticipation of a major action, the submarines may be deployed on the surface across or flanking the line of advance of the enemy heavy ships. If possible the deployment is made during darkness or low visibility or under cover of an aircraft screen, so that the disposition of the submarines will not be disclosed to the enemy. It is normally completed in time to permit undetected submergence in positions from which attack can be delivered.
933. Submarines that are initially unfavorably situated for attaining an attack position prior to a major action may be so disposed as to permit them to attack the enemy's heavy ships in case of a reversal of the action, or to sink damaged enemy heavy ships which may withdraw or fall out of his battle line.
934. In cases when it is probable that the enemy will retire to a known base or area, such submarines as have been unable to attack during the major engagement and submarines no longer in position to attack but having torpedoes remaining, may be disposed along the enemy's line of retreat for the purpose of attacking as he retires.
Section V. Submarines Cruising in Company With or in the Vicinity of Friendly Forces
937. If it is necessary for submarines to pass through a disposition or formation they do so on the surface and are escorted by one or more surface vessels. All task subdivisions are informed of the movement.
938. It may be expected that a submarine will never emerge in the presence of friendly surface craft or aircraft, except in an emergency, without first establishing its identity.