Air Fronts: Air Defense FM 44-8; Antiaircraft Operations Room and Antiaircraft Artillery Intelligence Service - Chapter 1. General

Section I. INTRODUCTION

1. PURPOSE. This manual describes the principles, functions, organization, and operation of the warning system within AA units, including the Antiaircraft Operations Room (AAOR), pronounced "double AOR," and the Antiaircraft Artillery Intelligence Service (AAAIS), pronounced "triple AIS." The AAOR and AAAIS are so closely allied that any complete discussion of one must necessarily include a discussion of the other. It is intended as a guide only and does not lay down inflexible rules. All commanders must be encouraged to solve each problem by the use of sound principles and good judgment and not by the blind application of rules.

2. REFERENCE. Publications containing related and additional information on subjects discussed in this manual, as well as other pertinent references, are listed in appendix V. This manual should be studied in conjunction with the listed references. For definitions of unfamiliar terms, refer to TM 20—205 as well as to the listed references.

3. NECESSITY FOR WARNING. Adequate warning of the approach of aircraft is essential to the most effective utilization of antiaircraft equipment and personnel. Without adequate warning all elements of the AA defense would have to be maintained in a state of readiness for instantaneous action. Such a state of readiness would require additional personnel to operate as reliefs, and additional equipment because it is impossible to provide continuous operation of power plants and radars. Time must be allowed for temporary shut-downs for necessary repairs and maintenance.

4. TYPES OF WARNING. a. There are three common types of warning.

(1) For automatic weapons, warning consists of notification that a target is only a few miles away. Such warning permits minimum manning details to take their posts at the guns, and point the guns in the direction of approach of the target. It is also desirable that sufficient warning time be obtained so that the director can be manned and operating when a target comes within the field of fire of the fire unit.

(2) For gun and searchlight units, there must be warning in sufficient time to permit the radars to warm up and get "on the air" if the state of readiness does not prescribe that radars are already "warmed up" (approximately 15 to 20 minutes required to warm up a cold radar).

(3) For gun and searchlight units a subsequent warning is needed so that the crews, other than the radar crew, may take their posts at their equipment in sufficient time to engage the target.

b. Warning of the type mentioned in a(1) above is generally obtained from a ring of observers at OP's. Where automatic weapons, guns, and/or searchlights are combined in the defense, additional warning may come from AAA radars. Warning from radars in the AA defense or from the AWS will come through the AAOR.

c. Warning of the type mentioned in a(2) above must come from a source outside the AA defense such as air force, naval, or civilian observer organizations. An AAA liaison officer transmits the information to the AAOR. The AAOR then passes the information to the units concerned.

d. Warning of the type mentioned in a(3) above usually comes from the AAA itself. Radars, having been put "on the air" as a result of the warning received in c above pick up the target and alert their own units. However it is entirely possible that the latter warning may he received from the AAOR based on reports from distant OP's or from continued early warning received from the liaison officer.

Section II. ANTIAIRCRAFT OPERATIONS ROOMS

5. GENERAL. a. The AAOR is the tactical or battle head-quarters of an antiaircraft defense. It is the collecting, evaluating, and disseminating center of the AAAIS.

b. An AAOR is normally organized and operated in each antiaircraft defended area by the highest AAA headquarters in the defense. In large defended areas an AAA operations detachment (T/O and E 44–7) may be provided to operate the AAOR. When an AAOR detachment is not provided, the principles and procedures are the same, but the operating personnel and equipment are drawn from the units of the defense. If searchlight battalions are present in the defense, the majority of the operating personnel may be drawn from the headquarters batteries of these units.

6. COMMAND. The AAOR is under the command of the antiaircraft defense commander. He is responsible for its organization and operation. He normally delegates the duty of organizing the AAOR and training the personnel to the S—2 on his staff. See FM 4—100 for the chain of command.

7. FUNCTIONS. a. The AAOR is the center for coordinating all the AA means available to engage the enemy as effectively as possible. To do this, the AAOR has two primary functions:

(1) To collect, evaluate, and disseminate intelligence.

(2) To exercise fire direction when and as necessary.

b. The AAOR performs other functions but they must be subordinate to and never interfere with the primary functions listed above. Some of these secondary functions are:

(1) To act as a center for liaison and coordination with other arms, services, and civil authorities.

(2) To provide higher and adjacent headquarters with pertinent information.

(3) To provide the antiaircraft defense commander with information on the efficiency and effectiveness of the defense.

(4) To perform certain routine functions, such as the collection and dissemination of meteorological data and the preparation of necessary reports. (See FM 4—100.)

c. For details see chapters 2 through 5.

8. AAOR FACILITIES. When setting up an AAOR the available facilities must be utilized. In small mobile defenses the AAOR may be set up under a tent fly. In large defended areas such as ports and cities it is desirable to use space in a permanent building such as a hotel or office building. The size and complexity of the AAOR and AAOR equipment is determined by the—

a. Size and permanency of the defense.

b. Number and type of AA units employed in the defense.

c. Space and facilities available.

9. AAOR's IN COMMUNICATIONS ZONE AND ZONE OF INTERIOR. AAA units engaged in active air defense in the communications zone and zone of the interior are under the command of the air force air defense command (fighter command) responsible for the active air defense of the area concerned (see FM 4-100 and 1-25).

a. An AAOR is established in each air defense region by the region AA commander if all AAA in the region is allocated to one defended area.

b. If the AAA in the region is split among several defended areas, an AAOR should be established in each such defended area. In this case the region AAOR should be eliminated.

10. AAOR's IN COMBAT ZONE. All AAA units in the combat zone, except such AAA units as are allocated to the tactical air command for the defense of its installations, are under the command of the ground field forces responsible for the portion of the combat zone concerned (see FM 4-100 and 1-25).

a. An AAOR is normally established for each AA defended area in the combat zone by the highest AAA headquarters in the division, corps, or army area concerned.

b. The number of the AAOR's established by the AAA units in the tactical air command will vary with the number and location of the airdromes to be defended. If such airdromes are widely separated it may be desirable to establish a small, simple AAOR at each defended airdrome.

11. AAOR's IN AMPHIBIOUS OPERATIONS. a. The AAOR does not function while the AAA units are afloat. All intelligence, commands, and data (if any) come from the air installations afloat. Such control continues until AAA units are ashore and operating under their own AAOR. Communication is by radio only.

b. AAOR's are established ashore according to geographical location of units. For example, unless two landing beaches are close together, a separate AAOR is established at each beach. Communication is entirely by radio. If the AAOR's are so close that the AAAIS radio nets jam each other, the AAA units should operate under one AAOR. The AAOR's established ashore are simple and extremely mobile.

c. The AAA units are grouped and consolidated under a normal combat zone AAOR (see par. 10) as rapidly as the situation permits, and thereafter function as described in subsequent chapters.

12. LOCATION OF AAOR. The AAOR is located at or near the center of the defense so that the length of telephone lines and radio nets between the AAOR and elements of the defense is as short as possible. However, security of the AAOR may be more important than mere geographical location. Possible damage to the AAOR and its communications as a result of air attack on the defended area must be considered in selecting the AAOR location. In small defenses, it may be desirable to locate the AAOR outside the defended area for this reason. An inconspicuous location is chosen and no attempt is made to provide antiaircraft protection specifically to defend the AAOR. Existing shelter is used when available and is camouflaged and reverted as soon as practicable after the AAOR is established and operating. When possible the AAOR should be "dug in" and all communication installations must be well protected.

13. LOCATION IN COMMUNICATIONS ZONE AND ZONE OF THE INTERIOR. a. AAOR's established by AAA units in the air defense area of air defense commands are located, whenever practicable, near the corresponding air force operations room. If possible the air force operations room and the AAOR are combined in the same room. It is particularly desirable that the AAOR and the air force operations room in a fighter control area be combined when the AA searchlights in that area are employed in the fighter-searchlight team.

b. Adjacent or combined location of AAOR's and corresponding air force operations rooms results in

(1) A decrease and simplification of communications.

(2) A saving in personnel, particularly tellers and liaison officers.

(3) Better coordination and more efficient operation of the entire air defense of the area.

14. LOCATION IN COMBAT ZONE. a. One AAOR established by army or task force AAA should be located as close to the tactical control center of the tactical air command as is practicable to lessen the necessary communication and improve the liaison. This AAOR should not, however, he combined with the tactical control center.

b. An AAOR established by the AAA units of the tactical air command may, if located nearby, he combined with the tactical control center.

15. EQUIPMENT. Regardless of the size of the defense, the equipment in the AAOR is essentially the same for all defenses. The size of the boards may change or the elaborateness of the equipment may vary, but basically it will be the same. In addition to the necessary communications, the equipment includes an AA operations board, a situation board, and a status board. The type and complexity of these boards and their appurtenances will vary, but they will always exist in some form.

16. AA OPERATIONS BOARD. (See fig. 1.) The in-formation on aerial activity needed by AA personnel for the purpose of alerting their units and furnishing them with the location and direction of attack is displayed on the AA operations board. The board, in its simplest form, may be an ordinary military map. The scale of the map or board and the size of the area covered will depend upon the size and type of defense. The board must show the defended area and its approaches. The operations board should be large enough to include the entire area in which the AAAIS elements of the defense can pick up targets (maximum detection range for radars, maximum visible range for OP's). The board is usually covered with transparent plastic or tracing paper to protect the board and facilitate erasures. No azimuth circles or range arms are used. All plotting is done in grid coordinates. The scale of the grid and the size of the grid numbers must be large enough to facilitate rapid plotting and to insure rapid evaluation and dissemination of data by the AAOO and assistants. For large defenses the board may be divided into segments for convenience in plotting. In addition to the display of the position and courses of aircraft the following items may be permanently shown on the board:

 
Figure 1. Typical AA operations board (for a defense of one gun battalion).

a. The standard Air Defense Grid, or the grid directed by the theater commander.

b. The defended area, important terrain features, and other pertinent information such as harbors, cities, and airdromes.

c. AA installations of the defense and their designations.

d. Boundary lines showing normal and contingent sectors for fire units and radars.

17. SITUATION BOARD. All warning information on friendly, hostile, or unidentified aircraft from sources other than local AAAIS is plotted on the situation board (see fig. 10), when such aircraft are outside the area covered by the operations board. When such plots are within the area of the operations board, the plots are transferred to or initially plotted on the operations board. The situations board is similar to the operations board in that the same basic grid is used. It uses a smaller scale and is normally mounted vertically. The situation board includes the area covered by the early warning agencies furnishing information to the AAOR. If the agencies furnishing early warning information use grid systems other than that used by the AA defense, these grids are also shown. Plots received in coordinates of other than the basic grid are converted. Distinctive colors are used for the grid lines to avoid confusion in plotting. Important terrain features, the defended area, AA installations, and other pertinent information may be shown on the situation board also.

18. STATUS BOARD. (See fig. 2.) The operating status of all units in the AA defense is posted on the status board. The use and design of the board depends upon the individual requirements of the particular AAOR. The board can be of any convenient size and is mounted vertically so that it can be read from all parts of the operations room. The following items are some of the information which may be shown on the status board:

a. Material status.

b. Meteorological data.

c. Time of sunrise and sunset.

d. Time of moonrise and moonset.

e. Operational schedule of radars.

f. Current aircraft recognition and identification signals.

g. Alert status of the elements of the defense.

h. Convoy information (for port defenses).

i. Friendly aircraft missions.

j. ROH (Ruling operational height) of barrage balloons.

k. Hours when smoke may be ordered.

 
Figure 2. Typical status board (adapt by additions or deletions to suit the defense).

19. DISPLAY STANDS. The display stand consists of an inclined wooden block which will receive four colored rectangles. In the top space a white rectangle indicating the radar position is displayed. In the second space a while rectangle showing the raid number is displayed. The third space is used to indicate the number and identity of the planes.

Figure 3. A type display stand.

A green tab is used for airplanes identified as friendly. A yellow tab is used for unidentified and a red tab for hostile air-planes. In the lower space, a white rectangle showing the altitude of the raid is displayed. On the altitude rectangle, the side marked with altitude in thousands of feet is displayed. The other side (with altitude marked in hundreds of yards) is for reference of plotter only. (See fig. 3.) This type of stand is suggested because it is easily constructed. Any stand that facilitates the display of target information may be used.

20. PLOTTING APPURTENANCES. Plotting is done using arrows or grease pencils. The arrows are improvised by cutting them from cardboard or plastic. They should be brightly colored. If the plotting board is large, rakes are necessary to move the arrows to the inner portion of the board. Grease pencil may be used to plot on vertical plotting boards.

21. PERSONNEL. The personnel necessary to operate an AAOR and the duties of these will vary with the type and size of the AAOR. Certain personnel and the performance of certain duties are always necessary. In some cases the duties may be combined, thus reducing the number necessary. In other cases the duties ordinarily assigned to one man may be so complex that it will be necessary to provide assistants and divide the duties among several individuals. The AAOR should be operated with the minimum staff consistent with the situation.

22. ANTIAIRCRAFT OPERATIONS OFFICER. The AA operations officer (AAOO) is the representative of the AA defense commander and is designated by him. He is responsible to the AA defense commander for the operations of the AAOR during his tour of duty. See chapters 2 through 5 for specific duties of the AA operations officer. In order to keep the duties of the operations officer to a minimum, it is imperative that every possible event, situation, or condition, be considered and that every detail that can possibly be pre-arranged be covered by standing operating procedure. (See FM 4-100.) The duties of the AA operations officer normally include the following:

a. To receive and evaluate information concerning friendly, unidentified, or hostile activity and pass it on to all concerned.

b. To exercise fire direction when necessary.

c. To determine the state of readiness of the units of the defense.

d. To determine and coordinate with friendly air forces the employment and ROH of barrage balloons.

e. To determine, in conjunction with friendly air force and smoke agencies, when smoke should be employed.

f. To observe and analyze all operations in order to deter-mine the efficiency of the defense and where necessary to correct the deficiencies noted.

g. To restrict fire in coordinated actions with friendly air forces.

h. To advise all units of the expected missions of friendly aircraft.

i. To receive meteorological data and to disseminate them to the units of the defense.

j. To supervise the operations in the AAOR.

k. To obtain and distribute identification and recognition signals to units of the defense.

l. To insure that an AAOR operation journal is kept (see fig. 11).

m. To shift sectors of search for radars when necessary.

n. To relay all information of a suspicious nature to interested agencies.

23. COMMUNICATIONS OFFICER. The communications officer is responsible for the installation, maintenance, trouble shooting, and proper operation of all radio and wire nets installed by the AAOR. He is designated by the AA defense commander and supervises the training of the communications personnel. See chapters 2 through 5 for specific duties of communications officers.

24. PLOTTERS. Plotters are used to make visual displays of current data on the operations board, situation board, status board, and any other necessary boards or maps. See chapters 2 through 5 for specific duties of plotters.

25. SWITCHBOARD OPERATORS. The switchboard operator is a key man in the AAOR. The efficient operation of switchboards requires careful training and dexterity. Flexibility of circuits and speed in breaking and remaking circuits is essential. For the specific duties of switchboard operators refer to chapters 2 through 5. The switchboard operator at the AAOR may at times operate more than one switchboard.

26. LIAISON. Effective liaison must be established with AAOR's in adjacent areas and with air force operations rooms. This liaison is necessary to coordinate the AA defenses of adjacent areas, to receive the early warning information available from air force installations, and to prevent AA fire on friendly aircraft. Liaison officers are furnished as consultants and are not in the chain of command.

a. In communications zone and zone of the interior. (1) Close liaison must be maintained between the AAOR and the controller in fighter control areas. For that reason, the AAOR should be located in the same building and, where space permits, combined with the fighter control area operations room, thereby eliminating the need for stationing an AAA liaison officer from AAOR in the fighter control area operations room. When the AAOR and the fighter control area operations room are not combined, the AAOR or higher AAA headquarters furnishes the AAA liaison officer.

(2) Region and air defense command AAA similarly maintain liaison with corresponding wing or air defense command operations rooms, and station an AAA liaison officer in the wing and air defense command operations rooms when the AA and air force operations rooms concerned are not combined.

(3) AAOR's in fighter control areas and regions maintain liaison with AAOR's in the same or adjacent fighter control areas and regions. The furnishing of liaison officers in these cases is usually unnecessary.

b. In combat zone. (I) AAOR's in division and corps areas maintain close liaison with AAOR's in adjacent division and corps areas. Corps AAA also maintains liaison with the AAOR's in subordinate divisions. Liaison officers are generally unnecessary in these cases. Corps AAA does not exercise command over division AAA except through the corps commander. In certain instances corps AAA, however, may re-strict the fire of division AAA (see par. 31b(1)).

(2) Army AAA maintains liaison with adjacent army and subordinate corps AAA. Liaison officers are generally not necessary for this purpose. Army AAA must maintain close liaison with the tactical control center of the tactical air command in the army area. Army AAA furnishes an AAA liaison officer at the tactical air command.

(a) Although close cooperation is necessary between the Army AAA and the tactical control center, tactical air command exercises no jurisdiction over the Army AAA.

(b) Army AAA exercises no command over corps and division AAA, except through the army commander. However, in some cases, Army AAA may restrict the fire of division and corps AAA (par. 31b(1) ).

(3) AAOR's established at tactical command installations also maintain liaison with the tactical control center, and will normally station an AAA liaison officer at the tactical control center for this purpose.

(4) Army AAA and the tactical air command AAA maintain liaison with each other through their respective liaison officers at the tactical control center.

27. TRAINING OF PERSONNEL. All personnel must be carefully and intensively trained to knit them into a coordinated team. Training in subjects such as combat intelligence, communications, map reading, and coordinate systems must be stressed. Every individual in the AAOR must be familiar with all the types of maps and grids that might be encountered. In addition to classroom instruction in these subjects many hours should be spent on command post exercises. These exercises should include canned and actual flights. The telephone and radio nets should be established to radars, OP's, and CP's. Simulated fire units with communications must be used to in-crease data available by transmitting canned courses. Simulated attacks on the defense should vary in intensity from simple nuisance raids to large scale raids that completely saturate the defenses and the AAOR. This training must continue until the personnel can establish and operate an AAOR for any type of defense and handle all probable types of aerial attacks. The training must be continuous, even after the formal training period has ended, so that no confusion will exist when an actual raid occurs.

28. OPERATIONS. The operations in different AAOR's will vary only in specific detail. The general operations are parallel and follow the same sequence. The operations start with the report of aerial activity from any warning agency. The reports are filtered, evaluated, and warnings sent to the fire units of the defense. In the meantime the operations officer studies the reports and plots, and exercises any necessary fire direction. The fire units engage the enemy in accordance with existing SOP and instructions received from the AAOR. For specific detailed operations and expected sequence of actions see chapters 2 through 5.

29. EMERGENCY FIRE CONTROL. Emergency fire control data will not be furnished from the plots displayed on the boards in the AAOR. Lateral lines will be established between gun batteries of the defense and present position data will be passed, when needed, over these lines. If these lines cannot be established, or if they fail, batteries are connected for emergency fire control purposes through the battalion switchboard. Only as a last resort should the batteries be connected through the AAOR switchboard for emergency fire control purposes. This procedure must be prearranged, so as not to clutter the AAOR communications during an enemy raid. See FM 4–121 for a complete discussion of emergency fire control procedures.

30. ALERT STATUS AND STATE OF READINESS. a. General. Alert status and state of readiness are not synonomous terms and should not be used interchangeably.

b. Alert status. (1) The alert status is the air raid warning alert issued to all active and passive air defense agencies in the area concerned. The alert status is prescribed by the agency charged with coordinating all air defense activities in the particular area.

(2) The various alert statuses are normally given color code names, such as "Yellow," "Blue," "Red," and "White" (all clear). (See FM 11-25.)

c. States of Readiness. (1) States of readiness for AA defense are prescribed in local SOP. The operations officer issues instructions on the state of readiness of the defense. These instructions are governed by the SOP, the alert status, and the aerial activity at the moment. The states of readiness are given code names or numbers. The operations officer always selects the most economical state of readiness that he believes will handle the situation. If the defense is alerted unnecessarily, and more personnel than are necessary remain at their equipment, the efficiency of the defense will decrease.

(2) These various states of readiness must be completely covered in SOP for both personnel and equipment. It must state such things as the distance of personnel from their equipment, in either time or distance; the number of personnel at the equipment, who they are, and their duties; what radars are on the air; what power plants will be "warming up;" status of ammunition; and other pertinent factors.

3I. FIRE DIRECTION. a. It may be necessary for the AAOR to exercise fire direction over one or more of the units in the selection of targets, and the distribution of fire. (See FM 4-100.) This is especially true in defenses employing guns and searchlights. In no case, however, should technical fire control be attempted from the AAOR. The final responsibility for the decision to engage any particular target must rest with the unit commander at the gun, automatic weapon, or searchlight position except when fire has been restricted. The fact that any other position has or has not engaged the target does not relieve each separate commander from making his own decision.

b. It may be necessary for the operations officer to exercise fire direction as follows:

(1) Restrict or limit fire in coordinate action with friendly air forces.

(2) Select targets for various portions of the defense in the case of large mass attacks, multiple attacks in various sectors, or attacks in successive waves.

(3) Assign portions of the defense to engage targets in certain zones; that is, normal zone, contingent zone, etc.

(4) Order some prearranged type of predicted concentration or barrage fire.

c. It is impossible to prescribe the fire direction necessary for all situations. The operations officer must weigh each situation and take the logical course of action. He must try to prevent the commitment of the fire of the defense on some feint or subsidiary attack, while the main effort remains unengaged. He must see that fire is distributed so the maximum number and the most important targets receive a proportionate share of the fire. He insures that surveillance is continuous, and if necessary, orders particular radars to search particular sectors.

Section III. AAAIS

32. GENERAL. a. AAAIS is organized for the collection, evaluation and dissemination of antiaircraft intelligence in an antiaircraft defense. It is an organized procedure for obtaining accurate information of aerial activity with which to warn the fire units of the defense of enemy attack or the approach of friendly aircraft. It provides them with timely information which will enable them to engage the enemy most effectively.

b. A well established AAAIS provides for the contribution of information by all elements of the defense, and the rapid distribution of pertinent intelligence to the units concerned.

c. An AAAIS permits the most economical employment of personnel. In a defense assured of adequate warning it will not be necessary to have complete manning personnel always at their equipment.

d. An AAAIS also insures the most efficient use of personnel and materiel. It insures that a greater number of targets will be engaged, that they will be engaged at maximum effective ranges, and that the fire brought to bear on enemy aircraft will be more intense and more accurate.

e. To be successful an AAAIS must furnish information rapidly.

33. RESPONSIBILITY. The antiaircraft defense commander is responsible for organizing and operating the AAAIS. He normally delegates this duty to the S–2 on his staff.

34. COMMUNICATIONS. The backbone of an AAAIS is its communications. Successful operation of any AAAIS is largely dependent on a high standard of maintenance of its signal system and the proper use of these communications. Speed and simplicity are essential in the operation of the communication net. A definite schedule of routine checks must be enforced to insure operation of all agencies in the required manner. Since several radios or telephones are often hooked into a single net, operators must be trained to use the common net in a manner that facilitates the orderly and prompt transmission of necessary messages. Wire and radio nets are used for the transmission of data, intelligence, commands, and administrative matters. Where time and material permit, parallel nets should be provided. Where the duties of an individual require the use of his hands or where he must move around to accomplish his job, some type of head and chest set must be provided. Relays must be kept to a minimum. The transmission of intelligence should be direct from its source to the interested elements of the defense. Relays and rebroadcasts result in time delays and inaccuracies. Radio and telephone procedure must be standardized with special emphasis on brevity,

35. WIRE VS RADIO. Whenever practicable the AAAIS of a defense uses wire communication supplemented by radio. Wire is generally more dependable, but in the early stages of an operation, time and conditions may prevent the use of wire. Radio must then be used. In such cases, wire is laid as soon as possible.

36. SOURCES OF AAAIS DATA. The AAAIS utilizes all available sources of intelligence in the defense. Information is gathered from all radars (gun laying, searchlight, and surveillance) and all observers. The radars provide the defense with accurate early warning information of aerial activity. Observers are used to supplement the radars and provide warning of fast, low-flying targets. The defense must be coordinated so that all possible avenues of approach are covered by both radars and observers.

37. RADARS. All radars in the antiaircraft defense may be utilized in the AAAIS. It is not practical to maintain all radars "on the air" at all times. The decision as to the number of radars required for adequate surveillance at one time must be made by the antiaircraft defense commander or his representative, the AAOO. This is normally covered by SOP. The gun, searchlight, and surveillance radars in the defense are connected by telephone to the AAOR. Plots are reported to the AAOR on all planes. Pertinent intelligence is then broadcast by the AAOR to all units of the defense. See chapters 3 and 4 for a discussion of how the reports are made.

38. OBSERVERS. a. Observers are antiaircraft personnel used to provide warning of the approach of fast, low-flying airplanes and other targets not picked up by radars. OP's, manned by observers, are established around the defended area. The distance of the OP's from the defended area and the spacing of the OP's around the defense are dependent upon the following:

(1) The terrain.

(2) The number of personnel and the amount of OP equipment available.

(3) The amount of warning time necessary.

b. No specific rules can be prescribed regarding the location and spacing of OP's. Generally, they should be located at the maximum distance from the defended area at which a complete coverage of all approaches can be obtained with the personnel and equipment available. Even this general rule will not always apply. The OP's would sometimes be so close that the warning received would be inadequate. In some such cases, it may be desirable to move the OP's further out, even though it means that the coverage will not be complete. When complete coverage is not possible, particular care should be taken to cover the likely avenues of approach. In other cases, the number of personnel and the amount of equipment available may be so great, that if the OP's were moved out to a maximum distance, the direction of approach of enemy planes reported by OP's would be unreliable. The enemy planes, in such cases, might be reported as they pass the ring of OP's and hover inside the ring without again being reported. Thus, the direction of approach reported by the OP's would be meaningless and the weapons would not be properly pointed. Sometimes the personnel and equipment may permit the establishment of two rings; one at a distance to give adequate warning so that fire units may man the equipment, start their generators, and be prepared to engage the target with director controlled fire; the other, closer in, to give accurate pointing information. In every case, the AA defense commander must carefully study the particular situation, decide the minimum warning time necessary and then locate his OP's in such a way that the necessary warning is obtained and the coverage, with the personnel and equipment available, is as complete as possible. Of course, the exact location and spacing will depend upon the terrain. Advantage should always be taken of any high points such as hills, mountains, towers, or trees.

c. Each OP should, whenever possible, be equipped with a radio of sufficient range to reach all fire units of the defense. It is particularly desirable that the warning be transmitted directly from the OP's to the fire units without any relay. Where sufficient radios to give an adequate coverage are not available, it may be necessary to supplement the radio equipped OP's with OP's employing telephones. , In such cases, the telephone OP's should be connected by wire to the closest radio transmitter that operates on the AAAIS frequency. The telephone OP reports are then broadcast by radio in the normal manner.

d. It may be necessary to establish OP's using unit radio or telephone equipment and personnel intended for other than AAAIS purposes. The defense commander must decide according to the situation and the urgency of the need for additional OP's, whether the shift in equipment and personnel is desirable. The use of equipment and personnel for purposes other than those intended should he kept to a minimum.

e. In addition to the OP's, air guards are needed in the AAAIS for close in warning. They are employed at all fire units to discover and report the approach of low-flying aircraft. These air guards permit other personnel at the fire unit to relax. It is sometimes necessary to have an air guard just over a nearby hill or beyond a clump of trees or other mask, to furnish warning and direction for the initial pointing of the weapons.

f. In coordinated defenses, each battalion or unit of the defense, is assigned a sector in which it must provide OP coverage.

39. OTHER INTELLIGENCE AGENCIES. To supplement the AAAIS and to facilitate liaison, the AAOR establishes direct communication with all other available air warning intelligence agencies operating in the vicinity, such as operations rooms and AWS agencies of air defense commands and tactical air commands, adjacent AA defenses, and naval installations (where appropriate). See paragraph 26 regarding the liaison to be established with such agencies. Any outside agency desiring to use AAAIS data must furnish the necessary tellers and communications equipment in the AAOR to transmit the information.

40. GRIDS. The successful coordinated operation of an AAAIS will depend largely upon the accurate location of all units of the defense by means of a grid system. The standard Air Defense Grid is used unless a different grid is pre-scribed for the theater of operations. For a complete discussion of grids see TM 44-225. If other intelligence agencies in the vicinity are not using the same grid as the AAAIS, provision must be made to convert intelligence data to the proper grid. This is done by superimposing, in distinctive colors, the other grids on the situation board used in the AAOR. The grid conversion is not done at the fire unit.

41. PERSONNEL. The personnel that organize and operate the AAAIS are obtained from the units of the defense. If necessary, personnel listed in the tables of organization to perform other duties must be utilized. This shift of personnel must be kept to a minimum. (See par. 5.)

42. SELECTION AND TRAINING OF OBSERVERS. The observers for the OP's must be carefully selected and trained. They must be selected early in the raining period and undergo intensive training. The standard for observers should be

a. Vision.      Vision 20/20 or correctible to 20/20.

b. Hearing. Aural acuity 20/20.

c. Intelligence. A.G.C.T. rating, not below Class III.

d. In addition, the observer must be proficient in

(1) Target Recognition. Expertly trained in recognition of aircraft and armored vehicles (FM 21-80).

(2) OP procedure. Proper transmission of flash messages.

(3) Establishment of OP. Selection, construction, occupation, and operation of an OP (FM 30-10 and 21-75).

(4) Observation. Ability to identify activities by sound or visual indications and estimation of altitudes, ranges, and directions (FM 30-10 and 21-75).

(5) Individual field messing and sanitation.

(6) Proficiency in local security and camouflage (FM 5--20, 5-20A, and 21-75).

(7) Map reading. With particular emphasis on distances, directions and grids (FM 21-25, 21-26, and TM 4-225).

(8) Radio and telephone procedure and maintenance (FM 24-5, 24-6, 24-9, 24-18, and TM's on radio and telephone equipment concerned).

(9) Use of binoculars (TM 9-575 and FM 23-55).

(10) Use of compass with which individual is equipped (FM 21-75).

(11) Driving truck, 1/4 ton (TM 10-460).

43. DIRECTION BOARD. Each OP and fire unit must have a direction board. The board is gridded with the grid used in the defense. It is used to determine the target location usually in grid coordinates. If this is not practical, the cardinal compass directions or clock directions are prominently shown and target location given by reference to them. The board should be of a color to blend with the terrain. It may bear merely a permanent blank grid which is lettered and numbered each time a new position is occupied. Grid coordinates of prominent terrain features are shown on the board. The board is oriented with respect to north. The OP (or fire unit) is near the center of the board. Range circles are drawn. The position of other OP's and fire units in the vicinity, as well as prominent terrain features are sketched on the board. The board should be approximately two feet square with a scale of about 1 inch = 2 miles (see fig. 4).

Figure 4. Typical direction board for an OP.

44. REPORTS FROM OP's. a. Reports from OP's are always made using the same form and sequence. Discipline must be strict and observers must not be permitted to deviate from the prescribed form. The length of the message and the sequence in which it is transmitted may have to be changed to meet the local situation.

b. (1) When reporting the location of a target in grid coordinates the first word of the message should be "Flash," to attract the attention of all those interested in receiving the report.

(2) The target is then located in grid coordinates. The observers must he trained to quickly estimate the location using four grid numbers. Unnecessary accuracy must not be attempted as it will only tend to delay the report and may result in an even greater inaccuracy. A letter prefix usually need not be used as the limits of the area covered by the OP's of a particular defense will not exceed the size of a fifth division square of the Air Defense Grid.

(3) The direction toward which the target is headed is reported using compass direction points each as: North, Southeast, Northwest, etc.

(4) The number of planes or vehicles is quickly estimated and reported. When a formation is large no attempt should be made to count the planes. The number should be estimated or they may be merely reported as "Many."

(5) The identity and kind of target is reported. Code names may be used such as; "Bandit" for an enemy plane, "Bogie" for an unidentified plane, and "Friendly" for a friendly plane. If the report refers to ground objects they are re-ported as "Tanks," "Trucks," etc. The report must never be delayed to obtain definite recognition. When in doubt, the observer should report them as unknown.

(6) The altitude of the target is given as "Low" or "High." The observer reports targets as "Low" if in his opinion they will be targets for the automatic weapons units of the defense. All other targets are reported as "High." No attempts should be made by an observer to estimate the altitude in yards or feet.

(7) The message is ended by giving the code description of the OP and the word "Out."

c. The sequence of a message, using grid coordinates to locate the target, is as follows:

1st word—"Flash."

2d word—"Seven-two-two-zero" (location in grid coordinates).

3d word—"Southeast" (direction plane headed toward) . 4th word—"Ten" (number of targets).

5th word—"Bandits" (kind and identity of target). 6th word—"Low" (altitude of plane).

7th word—"Queen, six, out" (code designation of the OP.

d. If it is not possible to use the grid coordinate system of locating targets, a clock system is employed. When using this system, 12 o'clock is North. The observer gives the clock direction from which the target is approaching the defended area. For example, if a target is approaching the defended area from the east the observer reports it as being at "3 o'clock" even though when he sees it, it may be at some other clock position with reference to his OP location. If it is not flying towards the defended area, he reports it as "Crossing," unless the target is leaving the area in which case he reports it as "Leaving." In either case he follows the word "Crossing" or "Leaving" with the direction in which the plane is headed. The remainder of the message is reported as prescribed in h above.

e. The sequence of a message, using the clock system where a target is flying toward the defended area, is as follows:

1st word—"Flash."

2d word—"3 o'clock" (direction of the target from the defended area).

3d word—"Ten" (number of targets).

4th word—"Bandits" (kind and identity of targets). 5th word—"Low" (altitude of plane).

6th word—"Queen six, out" (code designation of the OP).

f. The sequence of a message, using the clock system when the target is not flying toward the defended area, is as follows: 1st word—"Flash."

2d word—"Crossing" (indication that plane is not flying directly towards defended area).

3d word—"Southeast" (direction plane headed toward). 4th word—"Ten" (number of targets).

5th word—"Bandits" (kind and identity of targets). 6th word—"Low" (altitude of plane).

7th word—"Queen six, out" (code designation of the OP) .

g. It is not practicable to prescribe a system of reporting to be used in all situations. In early stages of operations before the elements of a defense are located in a grid system or when OP's are very close in, it may be desirable to merely report, "Flash, Queen Six." Such a report, in some cases, may give all the warning necessary and also give general gun pointing information. In every case the type of message employed must fit the needs of the defense. The defense commander must prescribe the form and sequence and then insist that there be no deviations from it. It is desirable to use the form and sequence stated in b above when the situation permits its employment.

h. The observer continues to report on a target once every minute so long as it is in sight. If a report is being transmitted from another OP, the transmission of the message is delayed until the other is completed.

i. Information on all targets reported upon is entered on a flash message form. (See fig. 5.) The recording of the message must never interfere with the prompt transmitting of it.

Figure 5. Flash message form.