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PART 1. GENERAL DOCTRINE

CONTENTS

CHAPTER 1. GENERAL AND MILITARY
CHARACTERISTICS

1101. The motor torpedo boat is a relatively small craft with great speed and striking power essentially offensive in character. Weapons consist of torpedoes, machine guns and usually depth charges. Its main defensive power lies in its small size, speed, maneuverability, ability to lay smoke and cruise silently at slow speeds.

1102. The primary mission of motor torpedo boats is to attack enemy surface ships. Their high speed, and torpedo armaments makes them most suitable for surprise attacks against enemy vessels on the surface, at night or during low visibility.

1103. Secondary functions which motor torpedo boats may be called upon at times to fulfill are listed as follows:

It must be borne in mind, however, that constant employment of these vessels for other purposes than for which designed, shortens the life of the boats, thus tending to reduce their effectiveness when called upon to fulfill their primary mission.

1104. To attain maximum effectiveness in motor torpedo boat operations requires a complete understanding of their capabilities. Like aircraft they require experienced and qualified

1105 (a) Success in motor torpedo boat operations requires extreme alertness and intelligence on the part of operating personnel. Surprise, deception, stealth, daring, and courage, are all elements favorable to success.

(b). It should not be necessary to state that the boat's armament must be kept ready for instant action on every wartime mission. Enemy contacts will occur after weeks and months of negative operations have tended to dull the appreciation of needs for such readiness. History is replete with instances of golden opportunities being lost through this neglect.

(c). Immediately an enemy is encountered there are two steps to be taken, (1) offensive action, the effectiveness of which depends strongly upon the promptness with which it is executed and (2) report to proper authority the presence of the enemy. In the excitement incident to the former, the latter should not be forgotten, and the ship's organization should provide means for insuring it is not neglected.

1106. Any commander directing motor torpedo boat operations for general or specific tasks, will give consideration to the characteristics and capabilities of the vessels, as noted below.

MILITARY CHARACTERISTICS

1107 (1) PT 20 type-PTs 20-68 (Elco Boatworks). Length 77 feet; beam 20 feet; maximum draft 5 feet; displacement 95,000 pounds.

(a) GUNS:

(b) AMMUNITION-20-mm.:

(c) TORPEDOES: Four 21-inch Mark 8-3C and D, speed 27 knots, range 13,500 yards. (If depth charges and 20-mm. gun are mounted, only two 21-inch torpedoes are carried, the other two are held in reserve.)

(d) TORPEDO TUBES: Four 21-inch Mark 18-1 bow launching. (Only two tubes mounted if 20-mm. gun and depth charges carried.)

(e) DEPTH CHARGES: Eight Mark 6 (300-pound charge).

(f) DEPTH CHARGE RACKS: Eight individual side launching type "C", or two (four charge each) stern launching.

(g) SMOKE SCREEN GENERATOR: Mark 3, capacity 32-gallon F. S. mixture.

(h) FRESH WATER: 180 gallons in two 90-gallon capacity tanks.

(i) FUEL: 3,000 gallons high octane gasoline.

(j) LUBRICATING OIL: 30 gallons.

(k) FRESH PROVISIONS: Four days' rations for nine men and two officers.

(l) COMMUNICATIONS: Blinker tube, semaphore, M. P. signal light, 8-inch searchlight, GF5, RU7, or TCS voice radio sets, range about 75 miles.

(m) RADIO DIRECTION FINDER: One R. D. F. per division in some squadrons, one R. D. F. per boat in other squadrons.

(n) MACHINERY:

(o) CRUISING RADIUS (see table in back of book):

(2) PT 71 type-PTs 71-94 (Higgins Industries).¹ Length 78 feet; beam ____ feet; maximum draft _____; displacement _____ pounds.

(a) GUNS:

(b) AMMUNITION-20-mm.:

.50-caliber:

.45-caliber:

(c) TORPEDOES: Four 21-inch Mark 8-3C and D, speed 27 knots, range 13,500 yards. (If depth charges and 20-mm. gun are mounted, only two 21-inch torpedoes are carried, the other two are held in reserve.)

(d) TORPEDO TUBES: Four 21-inch Mark 19 bow launching. (Only two tubes mounted if 20-mm. gun and depth charges are mounted.

(e) DEPTH CHARGES: Eight Mark 6 (300-pound charge).

(f) DEPTH CHARGE RACKS: Eight individual side launching type "C". -- ¹ Complete information not available and blank should be filled in when information is obtained.

(h) FRESH WATER: 200 gallons (approximate).

(i) FUEL: 3,000 gallons high octane gasoline.

(j) LUBRICATING OIL: 30 gallons.

(k) FRESH PROVISIONS: Four days rations for nine men and two officers.

(l) COMMUNICATIONS: Blinker tube semaphore, M. P. signal light, 8-inch searchlights, TCS voice radio set, range about 75 miles.

(m) RADIO DIRECTION FINDER: One R. D. F. set per boat.

(n) MACHINERY:

(o) CRUISING RADIUS (see table in back of book):

(3) PT 95 type-PTs 95-102 (Huckins Yacht Corp.)¹ length 80 feet; beam ____ feet; maximum draft ____ feet; displacement ____ pounds.

(a) GUNS:

(b) AMMUNITION-20-mm.:

50-caliber:

--
¹ Complete information not available and blanks should be filled in when information is obtained.

473319-42-2

.45-caliber:

.30-caliber:

(c) TORPEDOES: four 21-inch Mark 8-3 C and D, speed 27 knots, range 13,500 yards. (If depth charges and 20-mm. gun are mounted, only two 21-inch torpedoes are carried, the others are held in reserve.)

(d) TORPEDO TUBES: Four 21-inch Mark 19 bow launching (only two tubes mounted if 20-mm. gun and depth charges are mounted).

(e) DEPTH CHARGES: Eight Mark 6 (300-pound charge).

(f) DEPTH CHARGE RACKS: Eight individual side launching type "C."

(g) SMOKE SCREEN GENERATOR: Mark 3; capacity 32-gallon F. S. mixture.

(h) FRESH WATER: 200 gallons (approximate).

(i) FUEL: 3,000 gallons high octane gasoline.

(j) LUBRICATING OIL: 30 gallons.

(k) FRESH PROVISIONS: Four days rations for nine men and two officers.

(l) COMMUNICATIONS: Blinker tube, semaphore, M. P. signal light, 8-inch searchlight, T. C. S. voice radio set, range about 75 miles.

(m) RADIO DIRECTION FINDER: One R. D. F. set per boat.

(n) MACHINERY:

(o) CRUISING RADIUS (see table in back of book):

(a) GUNS:

(b) AMMUNITION:
20-mm.:

.50-caliber:

.45-caliber:

.30-caliber:

(c) TORPEDOES: Four 21-inch Mark 8-3 C and D, speed 27 knots, range 13,500 yards. (If depth charges and 20-mm. gun are mounted, only two 21-inch torpedoes are carried, the others are held in reserve.)

(d) TORPEDO TUBES: Four 21-inch Mark 18-1 bow launching (only two tubes mounted if 20-mm. gun and depth charges are mounted).

(e) DEPTH CHARGES: Eight Mark 6 (300-pound charge).

(f) DEPTH CHARGE RACKS: Eight individual side launching type "C".

(g) SMOKE SCREEN GENERATOR: Mark 3, capacity 32-gallon F. S. mixture.

(h) FRESH WATER: 200 gallons (approximate).

(i) FUEL: 3,000 gallons high octane gasoline.

(j) LUBRICATING OIL: 30 gallons.

(k) FRESH PROVISIONS: Four days rations for nine men and two officers.

(m) RADIO DIRECTION FINDER: One R. D. F. set per boat.

(n) MACHINERY:

(o) CRUISING RADIUS (see table in back of book):

CHAPTER 2. EMPLOYMENT

1201. Rough seas, especially from ahead, reduces the effectiveness of the boats and limits the endurance of the crews. However, in surprise attacks the enemy should, if practicable be approached from down wind unless engines are muffled.

1202. The wakes of motor torpedo boats at high speeds are visible considerable distances, both from the air and surface. The wake of center engine is less visible than that of wing engines. These factors should always be considered when planning operations unless satisfactory wake camouflaging apparatus is installed.

1203. Comparative difficulty of detection, when properly camouflaged is characteristic favorable to the motor torpedo boat type. Surprise is one of its potential offensive weapons. This will lead to employment of these vessels in unsupported operations, mostly at night or in low visibility.

1204. Employed in tactical units of relatively large numerical strength, the motor torpedo boat squadron becomes a powerful offensive weapon. These squadrons may operate from a fleet base or from the motor torpedo boat carrier. It has been considered feasible to develop a carrier by which squadrons of MTB's could be carried, launched and recovered at sea.

1206. In cases of necessity, motor torpedo boats armed with depth charges, radar and portable listening gear might be employed effectively off shore combatting enemy submarine attacks against coastal shipping. During daylight operations of this kind, the motor torpedo boats should operate in coordination with aircraft or disguised as fishing vessels. During night or low visibility motor torpedo boats could operate with larger radar equipped vessels or separately, relying on their potential surprise features to encounter and attack with torpedoes, guns, and depth charges, submarines which were proceeding on the surface.

1207. In harbors and shallow water areas, where specially small type enemy submarines have operated, motor torpedo boats have proved effective in combatting them. In this connection, motor torpedo boats are at present the only vessels which can launch depth charges in shallow water and successfully escape damage from their explosions.

1208. Motor torpedo boats have been employed for coastal and harbor approach escort duties. However, their limited sea keeping qualities and short cruising radius restrict this employment to emergency conditions.

1209. When motor torpedo boats are based so that enemy waters are within their cruising radius they can be used to lay mines close inshore and in harbor entrances using depth charge racks to carry the mines.

1210. Every effort must be exerted by motor torpedo boat personnel to obtain the greatest results with actual and potential weapons, which is inflicting maximum damage on the enemy. In no case should a vessel sink with torpedoes or ammunition on board if they can be fired at an enemy.

1211. Instructions governing the uses and procedures in handling actual weapons are contained in part 4 of this publication. The general doctrines to be observed follow in the next chapter.

CHAPTER 3. ATTACK DOCTRINE

Daylight Torpedo Attacks

1301. The considerations governing torpedo attacks differ widely depending:

(a) Whether attacks are to be made in daylight high visibility or at night and during low visibility.

(b) Whether massed attacks will be conducted by several squadrons or individual attacks by units of a squadron.

(c) On the type of enemy to be attacked and whether attack is to be supported or unsupported.

1302. Daylight attacks under good visibility conditions might be launched upon the following objectives:

(a) Attacks upon enemy merchantmen.

(b) Massed attacks upon enemy convoys.

(c) Attacks upon enemy raiders or convoys under cover of a smoke screen.

(d) Supported attacks in fleet actions if operating from a fleet base or carrier.

1303. The effectiveness of these types of attacks depends primarily upon the density of torpedoes which pass through the enemy formation.

1304. The majority of torpedo misses usually pass astern. Every effort should be made to plan the approach so the firing point is well on the enemy bow. Motor torpedo boats will be less visible on an approach from ahead; it is likely the enemy will have less fire power directly ahead; and if the enemy changes course in either direction there still remains a possibility of obtaining an attractive track angle.

1305. The effectiveness of a daylight attack may be augmented by the following factors:

(a) Simultaneous massed attacks pushed home to close ranges.

(b) Support of other craft in countering opposition.

(c) Approaching under cover of smoke.

(d) High-speed and zigzag approach.

(e) Avoiding enfilade.

1306. If circumstances do not favor or warrant an expectation of successful escape, motor torpedo boats will close to an absolute decisive torpedo firing range.

1308. The type of enemy being attacked and whether the attack will be supported or not, will usually determine the attack plan to be employed. Attack plans are covered in part 3 of this publication.

CHAPTER 4. ATTACK DOCTRINE

Night and Low Visibility Torpedo Attacks

1401. The effectiveness of an attack under these conditions depends primarily on approaching the enemy to close ranges undetected, where a reasonably accurate estimate may be made of his rate and direction of movement.

1402. In planning an attack at night or in low visibility, means of augmenting its effectiveness will usually be governed by:

(a) Accurate information of the enemy position, course and speed.

(b) Selection of favorable approach area based on enemy position, state of wind and sea.

(c) Full exploitation of surprise element.

(d) High speeds after decision is made to attack.

(e) Coordination of attack units and wave attacks.

(f) Firing torpedoes at close ranges.

(g) Coordination of attack with aircraft or other surface units.

1403. The possibility of reaching favorable positions at close range undetected are enhanced by the following factors:

(a) Silent approach, (engines muffled) with a favorable wind.

(b) Invisible wake. ( Slow speed or a choppy sea or wake camouflaged.)

(c) Minimum silhouette presentment. (Bow pointed toward the enemy.)

(d) Proper camouflage. (Hull and superstructure completely nonspecular. No reflecting surfaces.)

1405. Motor torpedo boat personnel must acquire a sense that will tell them whether at night they can be seen by the enemy or not. Generally speaking there is a tendency to underestimate distances at night.

1406. Similar to daylight attacks the most desirable approach is from ahead, and the firing point should always be well forward of the beam.

1407. When sea and weather conditions are unfavorable for close observation, it may be practicable at times to lie to, in areas where the enemy will have to pass through.

1408. When suddenly encountering an enemy at night undetected from an unfavorable attack position, and conditions warrant, engines should be reversed, backing away well clear, before increasing speed to gain a more favorable position. This will decrease chances of being detected by the wake.

1409. In planning an attack on an enemy force of heavy ships tightly screened by lighter forces, consideration should be given to the following:

1410. After contact with the enemy has been established at night, it is usually desirable to conduct attacks by individual boats considerably dispersed.

1411. When the objective enemy force is well screened it will sometimes be profitable under certain conditions, to trail the enemy from ahead and outside his range of motor torpedo boat detection, in order to fully develop the enemy formation, disposition and composition. This may increase the chances of filtering -through the screen later to reach the main objective.

1412. In firing torpedoes at very close ranges the distance required for the exploder to become fully armed, should always be considered.

1413. The fact that the enemy illuminates with a searchlight in the near vicinity of the motor torpedo boat does not always indicate that the boat has been discovered. Searchlight rays

1414. When contact with the enemy has been made and a closer or better attack position is considered desirable, further maneuvers should be made in a manner that will permit discharge of appropriate weapons instantly. For example: all guns should be prepared and directed at the enemy, a lead angle maintained for discharging torpedoes, all unclutched engines ready for immediate engagement and the smoke screen generator ready for immediate operation.

CHAPTER 5. ATTACK DOCTRINE

Depth Charge Attacks-Anti-Submarine Operations

1501. After expenditure of torpedoes, the opportunity to depth charge surface vessels may arise, particularly at night, and should be seized whenever possible. By proceeding at high speed across the enemy's bow, and launching depth charges set at shallow depths, severe damage to an enemy surface vessel may be inflicted. During the course of this operation a heavy volume of machine gun fire directed at bridge and control stations should be maintained.

1502. Depth charge attacks delivered in the daytime would normally consist of the following:

(a) Attacking a periscope which had been sighted.

(b) Depth charging in spots where other indications on the surface made it appear that a submarine was operating, submerged.

(c) Depth charging spots at the direction of aircraft, when working in conjunction with aircraft.

(d) Depth charging spots where listening or other form of sound apparatus indicated the presence of a submarine.

1503. When attacking a periscope which has been sighted, every effort should be made to determine as accurately as possible the rate and direction of its movement. An analysis of unsuccessful depth charge attacks made in the present war,

The British have analyzed the situation and have stated that the lethal distance of a depth charge explosion depends on the type of submarine attacked and position of damage on hull. Also that the distances given below are generally accepted as the maximum for a "kill," while explosions at double the distances may bring a submarine to the surface.

1504. A submarine, submerged at periscope depth, may be from 50-75 feet under the surface. Depth charges exploded under a submarine will probably do more damage than those exploding above. Therefore, if a periscope is sighted and the attack launched immediately thereafter, the first depth charges should be set at least 50-100 feet and later ones set at great depths.

1505. When a submarine is actually known to be operating in the vicinity it should be hunted relentlessly. If it is not possible to destroy the submarine it should be kept down and made to use up reserve battery energy. Running slow it is possible for a submarine to remain submerged no longer than about 48 hours.

1506. A submerged submarine may give off air bubbles or show traces of oil. Approximate speeds of ascent of oil and air may be accepted as:

An oil streak from a submerged submarine would probably be V shaped and quite clearly defined. In any case the importance of "lead" should not be forgotten since the submarine will definitely have way on, and the one place he will not be is the exact spot where he was last seen.

1508. If independent operations against enemy submarines or surface vessels are contemplated some distance off shore by motor torpedo boats, it probably would be feasible for the latter to be disguised as fishing vessels during daylight for the run out, and remove the disguise during hours of darkness.

1509. Successful antisubmarine operations by motor torpedo boats are most likely to be effected at night in off shore areas, where submarines may be attacking coastal shipping or convoys, or where submarines may attempt to shell strategic points. Nearly all successful enemy submarine attacks at night have been made from the surface.

1510. The possibility of a motor torpedo boat encountering, surprising, and torpedoing an enemy submarine on the surface at night is not too remote. However, such an encounter will require extreme vigilance, alertness and quick action on the part of motor torpedo boat personnel, since the submarine will probably also be maintaining a careful and vigilant lookout watch.

1511. An enemy submarine proceeding on the surface at night would probably elect, at the first sign of danger, to defend itself with gunfire or to crash dive. In case of the former, a heavy volume of machine gun fire directed at the conning tower and gun stations, followed by firing torpedoes would be most effective. In case of the latter, rapid discharge of torpedoes followed by a depth charge attack would be most effective. In any event during daylight or darkness, the entire motor torpedo boat armament must be manned and ready for instant use.

1512. Submarines use Diesel oil, which is a light oil having a distinctive and rather strong odor. If wind conditions are favorable, a submarine on the surface charging batteries at night might be detected by smell of the oil considerably farther away, than by sighting him.

1513. Motor torpedo boats equipped with radar, operating in conjunction and communication with a larger vessel such as tender equipped with radar, are further considerations for night antisubmarine warfare.