• 9. ROLE.—a. Tank destroyer units are especially designed for offensive action against hostile armored forces. They are capable of semi-independent action but preferably operate in close cooperation with friendly units of al arms. They are allocated to large units as indicated in paragraph 36.

b. When supported units are engaged in offensive action, tank destroyers protect them against armored counterattack and thus allow full exploitation of their success.

c. When a supported unit is engaged in defensive action, a minimum of antitank weapons are located to cover obstacles and establish a first echelon of defense disposed in depth against tanks while a maximum of mobile antitank weapons are held in reserve, prepared for immediate offensive action. Organic antitank weapons of front line units are used for this first line of defense; tank destroyer units form the mobile reserve.

• 10. CHARACTERISTICS.—a. The characteristics of tank destroyer units are mobility and a high degree of armor-piercing fire power, combined with light armor protection; strong defensive capacity against attacks of combat aviation; and flexibility of action permitted by generous endowment with means of communication. Tank destroyer units are also capable of effective action against tanks through the use of close combat weapons.

b. Action of tank destroyer units is characterized by rapid movements, sudden changes in the situation, and a succession of brief but extremely violent combats separated by sporadic lulls. Aggressive fighting spirit and individual initiative are marked features.

c. Highly effective against tanks, tank destroyers are ill suited to close combat against strong forces of hostile foot troops.

• 11. MISSION.—a. As indicated by their name, the primary mission of tank destroyer units is the destruction of hostile tanks.

b. When tank destroyer units can be spared from this primary mission, they may be employed on secondary missions, such as beach defense, action against parachute and air-borne troops, and the reduction of bunkers, pill boxes, and other weapon emplacements. The decision to employ tank destroyer units on other than primary missions is a responsibility of higher commanders.

• 12. TANK DESTROYER SPIRIT.—Tanks and armored cars can be destroyed only by tough and determined fighting men who are masters of their weapons. Tank destroyer soldiers are taught that they must be superior soldiers. The moral qualities of aggressiveness, group spirit, and pride in an arduous and dangerous combat mission must pervade each tank destroyer unit. All ranks must possess a high sense of duty, an outstanding degree of discipline, a feeling of mutual loyalty and confidence with regard to their comrades and leaders, and a conscious pride in their organization.

• 13. LEADERSHIP.—The tank destroyer spirit can be developed only through the highest type of leadership. Detailed discussion of this military requisite is found in FM 100-5. The encouragement of initiative is a salient feature of leadership in tank destroyer units.

• 14. SELF-PROPELLED MOUNTS.—a. Types of weapons.—The primary weapons of tank destroyer units are sell-propelled guns with high velocities and flat trajectory. These vehicles provide limited armor protection to crews and can move into and out of firing position rapidly. The guns are of several different calibers.

(1) 37-mm gun.—The general characteristics of this weapon are given in FM 23-70. It is capable of effective action against the majority of tanks at ranges of 500 yards or closer and against light tanks and armored cars at greater ranges. Its fire must be directed against the more vulnerable portions of heavily armored tanks. Several hits may be required to knock out such vehicles. Its projectile loses penetrating power rapidly as the impact varies widely from normal. Its high mobility, rapidity of fire, ease of concealment, and the light weight of its ammunition fit this weapon particularly for delaying, harassing, and security missions and for action against hostile armored reconnaissance elements and light tanks.

(2) 75-mm gun.—The general characteristics are given in TM 9-305. Using armor- piercing ammunition, this cannon is effective against most tanks at ranges up to 1,000 yards. The heavy impact of the projectile may disable a tank at greater ranges without necessarily penetrating its armor. This is particularly true of hits on the tracks, drive sprockets, and on the turret.

(3) 57-mm gun.—This weapon has slightly greater penetrating power than the 75-mm gun and is capable of destroying most tanks at ranges of 1,000 yards or greater.

(4) 3-inch antitank gun.—This weapon when firing armor- piercing ammunition has tremendous tank destructive powers. A single projectile will usually disable any tank that is solidly struck at ranges up to 2,500 yards.

b. Types of ammunition.—All armor-piercing ammunition for the weapons listed above carry a visible tracing compound in the base of the projectile. This greatly facilitates the adjustment of fire on moving targets. A small proportion of high explosive ammunition for use against personnel is usually carried with these weapons. The high explosive ammunition of 3- inch guns is effective against tanks as well as personnel. If armor-piercing projectiles for the 75- mm gun are lacking, unfuzed shell should be fired against tanks; otherwise smoke of the first explosion may obscure the target.

c. Methods of fire control.—Direct laying is habitually employed by tank destroyer guns. Under exceptional circumstances, such as the definite location of a large mass of tanks at long range, the heavier calibered weapons may employ simple methods of indirect laying, the fire being adjusted by an observer in a forward armored mobile observation post. High explosive ammunition will be used. Ammunition to be expended under these circumstances must be made available by the supported unit; weapons must always retain adequate ammunition for their principal method of action against tanks.

• 15. TOWED Guns.—Tank destroyer units may be equipped with towed guns of the same characteristics as those just described. Towed guns can be easily and quickly concealed but require considerably more time to get into and out of position. Improvised methods of porteeing towed guns may give them some of the desirable characteristics of self-propelled guns.

• 16. AUXILIARY WEAPONS.—The following auxiliary weapons greatly augment the effectiveness of tank destroyer units:

a. Antitank grenades.—The most powerful offensive adjuncts to the antitank guns of tank destroyer units are antitank grenades. These powerful short range weapons provide crews of self-propelled weapons with an effective means of combating and destroying tanks at close range if their primary weapon or its vehicle is disabled. They render every small reconnaissance and security detachment a dangerous menace to tanks. (See FM 23-30.)

b. Antiaircraft weapons.—Caliber .50 machine guns on suitable mounts provide antiaircraft protection against low-flying combat aviation and dive bombers. When not required for antiaircraft protection, they are used for augmenting destroyer fire against tanks.

c. Mines.—A limited number of mines is carried by tank destroyer units to block corridors or favorable tank approaches not covered by gun fire, for close protection of gun positions, for use in ambushes, and to canalize the advance of tanks Into areas that are covered by gun fire. The quantities carried are not sufficient to permit the laying of a large mine field. Promiscuous use of mines risks being as dangerous to friendly as to hostile troops; exceptional precautions are required in their employment. (See FM 100-5.)

d. Smoke-projecting devices.—Each combat vehicle carries a small number of hand smoke grenades and smoke pots. Smoke placed as a screen in front of destroyers neutralizes the accuracy of hostile fire, and permits unobserved maneuver. Even greater protection against fire results when the smoke is placed on the hostile tank or weapon. Tanks are blinded in passing through smoke, direction is frequently lost, speed of maneuver decreases, and if the immediate terrain is full of obstacles such as stumps, large trees, ditches, or streams, they may be immobilized. In addition to this, tanks emerging from a smoke cloud are sharply silhouetted against the white background and present an excellent target.

e. Individual weapons.—All personnel are armed with the pistol, the rifle, or the carbine for individual protection. In addition hand grenades are carried on each combat vehicle.

• 17. GENERAL.—a. The critical importance of time in tank destroyer operations, particularly during actual combat, demands that every possible method of rapid communication be employed. Two-way radio, both voice and code, is the principal method used, but complete reliance cannot be placed on this for all phases of operation. Additional means of communication include messengers (airplane, motor, motorcycle, and foot), visual signals (pyrotechnics, flashlights, flags, panels, and airplanes), liaison officers, and, in exceptional cases, telephones.

b. At all times, commanders should be prepared to utilize emergency communication in the event the enemy jams frequencies assigned to tank destroyer units and to the warning system. Plans for emergency use should include the utilization of all possible methods.

• 18. RADIO COMMUNICATION.—a. Two-way radio communication is provided for within the battalion down to and including platoon leaders. Certain section leaders are provided with receivers. Two-way cleared channels are allocated to battalions by higher headquarters for command and antitank warning service. (See ch. 11.)

b. The large number of sets in the battalion requires rigid net control and discipline, in addition to thorough training in operation and maintenance of all sets.

c. When in contact with the enemy, voice radio messages from platoons and companies, in principle, will be transmitted by officers. The officer is the combat operator and directs his unit, microphone in hand. During this period the regularly assigned operator keeps the set in operation, properly tuned, and receives and sends messages in the absence of the officer to whom the set is assigned. In the unusual case when it is impracticable for the .officer to act as combat operator, he writes out messages for transmission or dictates them phrase by phrase while remaining near the operator. In the latter case he listens to the transmission and instantly corrects errors. The officer is responsible for all errors and omissions.

d. Information of the enemy at times may be sent in the clear, but identifications of friendly troops, their location, operation, and movement are usually disguised by suitable simple codes. Destroyer unit commanders in transmitting orders and instructions by radio endeavor to use language understandable to the units receiving them but meaningless to the enemy. In addition to the prescribed brevity and map coordinate codes, destroyer battalion and company commanders may select identified terrain features in the zone of combat and designate them as reference points. Battalion reference points are lettered; those of the companies are numbered. Selection of more than two or three reference points by each unit is inadvisable. Mention of such reference points can be made over the air without divulging information to the enemy. Reference points will not be identified over the radio. Details of codes are covered in signal operation instructions of the particular unit. Provisions must be included in the preparation of such codes to permit their being quickly changed. Codes must be changed daily or more often during active operations.

e. Radio silence should not be imposed upon active reconnaissance detachments of tank destroyer battalions when combat is imminent.

• 19. ARM-AND-HAND SIGNALS.—a. Drill and combat arm-and-hand signals applicable to tank destroyer units are described in FM 18-15.

b. A few additional visual signals using colored flags, disks, blinkers (flashlights), and colored smoke may be used for the tactical control of small units. Attempts to employ a large number of signals usually lead to confusion. Such signals are included in the signal operation instructions (SOI) of the particular unit.

• 20. PYROTECHNICS.—Very pistols and ground projectors are furnished tank destroyer units. Due precautions must be taken to insure that the use of these signals will not confuse friendly troops with which tank destroyer units may be associated.

• 21. AIR-GROUND PANELS.—a. Air-ground liaison panels are used to supplement, and if necessary to substitute for, the usual radio communication with observation aviation. (See FM 24-5.)

b. In addition to these panels, plainly recognizable identification panels should be provided for battalion headquarters, and all observation aviation operating with the tank destroyer units informed in advance of their design. Small panels are of little value. The panel should be at least as large as the body of a tank destroyer, and should be of a color that can be easily seen.

c. In emergencies an airplane may communicate with ground troops by simple maneuvers of the plane while in flight. Any code devised should be prescribed in signal operation instructions.

• 22. MESSENGERS.—Motorcycle or motor messengers may be used to assist in clearing radio traffic, or when radio silence is in effect. They are used to deliver marked maps and sketches. Motorcycles are preferable if messenger routes are crowded with traffic. Motors (1/4-ton trucks) have much better speed in mud, sand, or cross country travel. Small units may use foot messengers when other means fall. When available, air-borne messengers provide the means for rapid transmission of important messages.

• 23. LIAISON OFFICERS.—Liaison officers are habitually used by tank destroyer battalions attached to large units, to insure that close contact with the commander is maintained. A liaison officer will always be sent to the headquarters of the supported unit. Often it will be advantageous to send a liaison officer to the headquarters of the reconnaissance unit of the supported organization. They are transported in organic vehicles equipped with two-way radio. If part of a tank destroyer group, a battalion sends a liaison officer to the group commander. (See par. 164.)

• 24. TELEPHONES.—Telephones, without wire, are carried in the battalion for use with higher headquarters. The higher unit furnishes wire if telephones are to be used. When operating in friendly territory, these telephones permit utilization of commercial wire lines, if available, and may be advantageously used to tie in with antitank warning service installations.

• 25. MAPS AND MESSAGES.—The use of simple maps, overlays, and sketches for dependable transmission of information assists in maintaining communication at the efficient peak required in tank destroyer operations.

• 26. GENERAL—a. The semi-independent nature of tank destroyer operations requires that tank destroyer units be self-contained. Personnel, equipment, and training of tank destroyer units conform to this necessity.

b. Tank destroyer units will be subject to alterations; changes of weapons, equipment, and details of organization may be frequent. Moreover, the exact amounts and types of prescribed equipment may not always be available. Tank destroyer commanders must develop the capacity to handle groupings which are formed as task forces.

• 27. TANK DESTROYER BATTALION.—The tank destroyer battalion Is the basic tactical unit for operation against enemy armored elements in conjunction with, or in support of, infantry, Cavalry, motorized, and armored divisions. The battalion consists of a headquarters and headquarters company, three tank destroyer companies, and a reconnaissance company. For details of organization and equipment, see T/O 18-25.

• 28. HEADQUARTERS AND HEADQUARTERS COMPANY.—a. Command, staff, administrative, personnel, motor maintenance and inspection, and supply echelons of the battalion are grouped in the headquarters company. For details of organization and equipment, see T/O 18-26.

b. This organization operates to free the combat companies from administrative and supply burdens. Kitchen, combat, gas and oil, ammunition trucks, and heavy maintenance vehicles are pooled. If companies are detached from the battalion, the necessary supply vehicles will accompany them.

• 29. TANK DESTROYER COMPANY.—a. The tank destroyer companies of the battalion, the main fighting element, are composed of a headquarters, one light destroyer platoon, and two heavy destroyer platoons. For details of organization and equipment, see T/O 18-27.

b. To insure that destroyers are given protection against hostile ground and air forces, security and antiaircraft elements are included in destroyer companies.

• 30. RECONNAISSANCE COMPANY.—The reconnaissance company is the principal information-gathering agency of the battalion. It consists of a headquarters, three reconnaissance platoons, and a pioneer platoon. For details of organization and equipment, see T/O 18-28.

• 31. TANK DESTROYER GROUPS.—Tank destroyer groups are organized for operations against large armored forces. Their composition may vary materially. The main striking force of the group consists of tank destroyer battalions. Other elements are attached in accordance with the mission of the group and the situation. The tank destroyer group is controlled, supplied, and administered by a headquarters and headquarters company organized in accordance with T/O 18-10-1.