Infantry Drills

FM 3-21.8 – Chapter 2 – Section V – Employing Indirect Fires

Section V – Employing Indirect Fires

2-123.  The purpose of this section is to discuss techniques associated with calling for and adjusting indirect fires.

Call For Fire

2-124.  The battalion fire support execution matrix may require the platoon to call for and adjust its own indirect fire support. Normally, the battalion fire support annex will designate company targets.  However, the matrix also might designate platoon targets. The platoon uses these preplanned artillery targets to call for and adjust indirect fire. Either a Soldier or a forward observer (FO) can prepare and request a call for fire. To receive immediate indirect fire support, the observer must plan targets and follow proper call-for-fire procedures. If available, he should use a GPS and laser range finder.

2-125.  The call for fire consists of required and optional elements. If the observer is untrained, FDC personnel are trained to assist him in the call-for-fire procedure and subsequent adjustments by asking leading questions to obtain the information needed. Optional elements, methods of engagement, and methods of fire and control require a relatively high level of experience, but are not necessary to get fire support.

Required Elements

2-126.  Calls for fire must include the following three elements:

– Observer identification and warning order.

– Target location.

– Target description.

Observer Identification and Warning Order

2-127.  Observer identification tells the fire direction center (FDC) who is calling. It also clears the net for the duration of the call. The WARNO tells the FDC the type of mission and the method of locating the target. The types of indirect fire missions are adjust fire, fire for effect (FFE), suppress, and immediate suppression.

Adjust Fire

2-128.  Use this command when uncertain of target location. Calling an adjust fire mission means the observer knows he will need to make adjustments prior to calling a fire for effect.

Fire for Effect

2-129.  Use this command for rounds on target, no adjustment. An example of this situation is if it is known that the target is in building X. Building X is easily identified on the map as Grid ML 12345678910.


2-130.  Use this command to obtain fire quickly. The suppression mission is used to initiate fire on a preplanned target (known to the FDC) and unplanned targets. An example is calling for fire to force the enemy to “get down and seek cover.” This should enable friendly forces to close with and destroy the enemy with direct fire.

Immediate Suppression

2-131.  Use this command to indicate the platoon is already being engaged by the enemy. Target identification is required. The term “immediate” tells the FDC that the friendly unit is in direct fire contact with the enemy target.

Target Location Methods

2-132.  When locating a target for engagement, the observer must determine which of the target location methods he will use: grid, polar, or shift from a known point.

Grid Mission

2-133.  The observer sends the enemy target location as an 8- or 10-digit grid coordinate. Before the first adjusting rounds are fired, the FDC must know the direction from the observer’s location. The observer sends observer-target (OT) direction (to the nearest 10 mils) from his position to the target (Table 2-7).


Table 2-7. Example fire mission, grid.

Initial Fire Request From Observer to FDC



GRID NK180513, OVER. GRID NK180513, OUT.

Message to Observer




For Subsequent Rounds (From Observer to FDC)



Note:  Send direction before or with the first subsequent correction.

Polar Mission

2-134.  The observer sends direction, distance, and an up or down measurement (if significant) from his location to the enemy target. The FDC must know the observer’s location prior to initiating the call for fire. The word “polar” in the WARNO alerts the FDC that the target will be located with respect to the observer’s position. The up or down correction is an estimated vertical shift from the observer’s location to the target and is only significant if greater than or equal to 35 meters. If the target is higher, it is an up correction. If the target is lower, it is a down correction (Table 2-8 and Figure 2-11). Normally, inexperienced observers only send a direction and distance and ignore the up or down correction.

Table 2-8. Example fire mission, polar plot.


Initial Fire Request From Observer to FDC




Message to Observer





Figure 2-11. Polar plot method of target location.

Shift From a Known Point

2-135.  Shift from a known point is performed when the observer and FDC have a common known point. The observer sends OT line and then determines the lateral and range shifts. The enemy target will be located in relation to a preexisting known point or recorded target. The point or target from which the shift is made is sent in the WARNO. (Both the observer and the FDC must know the location of the point or recorded target.) The observer sends a target/known point number, a direction, and left/right, add/drop, and up/down corrections as listed below (Table 2-9, and Figures 2-12 and 2-13):

– Direction from observer (grid azimuth in mils) to target.

– The lateral shift in meters (how far left or right the target is) from the known point (Figure 2-13).

– The range shift (how much farther [ADD] or closer [DROP] the target is in relation to the known point, to the nearest 100 meters) (Figure 2-13).

– The vertical shift (how much the altitude of the target is above [UP] or below [DOWN] the altitude of the known point, expressed to the nearest 5 meters). A vertical shift is usually only significant if it is greater than or equal to 35 meters.


Table 2-9. Example fire mission, shift from a known point.

Initial Fire Request From Observer to FDC



DIRECTION 5210, LEFT 380, ADD 400, DOWN 35, OVER. DIRECTION 5210, LEFT 380, ADD 400, DOWN 35, OUT.

Message to Observer





Figure 2-12. Shift from a known point method using direction (in mils).

Figure 2-13. Lateral and range shifts from a known point.


              Sergeant Orest Bisko, a patrol leader from the 1st Marine Force Reconnaissance Company, knew how to use artillery. When occupying an observation post, Bisko fired his artillery at a set of known coordinates. This would enable him to later shift from that known point to the target with speed and precision. On 26 July 1966, while his four-man patrol was occupying an observation post, they spotted a large collection of enemy encamped in a small, wooded grove. The enemy force, he observed, apparently was in no hurry to move. Sergeant Bisko deliberately whispered fire commands over his radio to his direct support artillery. He ordered them to shift the distance from the known target and fire for effect. Three minutes later shells began crashing into the enemy perimeter. After approximately 30 minutes, 50 enemy were dead and the patrol had escaped in the confusion.

Shifting from a Known Point

Small Unit Actions in Vietnam

Francis J. West

Target Description

2-136.  The target description helps the FDC to select the type and amount of ammunition to best defeat the enemy target. Following is a brief description of the target using the mnemonic SNAP:

– Size and or shape (“one enemy soldier” or “platoon of enemy soldiers”).

– Nature and or nomenclature (“T72,” “sniper team,” “machine gunner”).

– Activity (“stationary” or “moving”).

– Protection and or posture (“in the open,” “dug in,” or “on a rooftop”).

Message to Observer

2-137.  After the FDC receives the call for fire, it determines if and how the target will be attacked. That decision is announced to the observer in the form of a message to the observer (Tables 3-7, 3-8, and 3-9). The observer acknowledges the message to observer by reading it back in its entirety.

2-138.  Additionally, the FDC will send the following transmissions:

– Shot. The term SHOT, OVER is transmitted by the FDC after each round fired in adjustment and after the initial round in the fire for effect (FFE) phase. The observer acknowledges with SHOT, OUT.

– Splash. The term SPLASH, OVER is transmitted by the FDC to inform the observer when his round is five seconds from detonation/impact. The observer responds with SPLASH, OUT.

– Rounds Complete. The term ROUNDS COMPLETE, OVER signifies that the number of rounds specified in the FFE have been fired. The observer responds with ROUNDS COMPLETE, OUT.

Optional Elements

2-139.  A call for fire also might include the following information:

– Method of engagement.

– Danger close.

– Method of fire and control.

– Refinement and end of mission.

Method of Engagement

2-140.  The observer uses the method of engagement portion of the call for fire to tell the FDC how to attack the enemy target. The method of engagement consists of the type of engagement, trajectory, danger close (if applicable), ammunition, and distribution.


2-141.  A low-angle trajectory is standard without a request. A high-angle trajectory is at the request of the observer or when required due to masking terrain. An example of this terrain would be an enemy position in defilade on the backside of a mountain range. This allows the indirect fire munitions to successfully clear the top of the masking terrain and have more of a vertical descent, resulting in the munitions impacting directly on the enemy position.

Danger Close

2-142.  Danger close is announced when applicable. Include the term danger close in the method-of-engagement portion of the call for fire when the target is within 600 meters of any friendly elements for both mortars and field artillery. When adjusting naval gunfire, announce DANGER CLOSE when the target is located within 750 meters and naval guns 5 inches or smaller are in use. For naval guns larger than 5 inches, announce DANGER CLOSE when the target is within 1,000 meters. The creeping method of adjustment will be used exclusively during danger close missions. The forward observer makes range changes by creeping the rounds to the target using corrections of less than 100 meters.


2-143.  Ammunition is the type of projectile, the type of fuse action, and the volume of fire desired in the fire-for-effect phase stated in rounds per howitzer. The type of ammunition can be requested by the observer, but final determination is by the FDC based on Class V unit basic load and target description.

Method of Fire and Control

2-144.  The method of fire and control indicates the desired manner of attacking the target, whether the observer wants to control the time or delivery of fire, and whether he can observe the target. The observer announces the appropriate method of fire and control.

Fire When Ready

2-145.  FIRE WHEN READY is standard without request, and is not announced. The mission will be fired as soon as the data is processed, guns are laid on the target, and munitions are loaded.

At My Command

2-146.  If the observer wishes to control the time of delivery of fire, he includes AT MY COMMAND in the method of control. When the pieces are ready to fire, the FDC announces PLATOON (or BATTERY or BATTALION) IS READY, OVER. (Call signs are used.) The observer announces FIRE when he is ready for the pieces to fire. In certain scenarios, the observer must consider the time of flight for the munitions to leave the indirect fire system and impact on the target. The “time of flight” data can be requested by the observer and determined by the FDC. This only applies to adjusting rounds and the first volley of an FFE. AT MY COMMAND remains in effect throughout the mission until the observer announces CANCEL AT MY COMMAND, OVER.

2-147.  AT MY COMMAND can be further specified. BY ROUND AT MY COMMAND controls every round in adjustment and every volley in the FFE phase.

Time on Target

2-148.  The observer may tell the FDC when he wants the rounds to impact by requesting, for example, TIME ON TARGET, 0859, OVER. The observer must ensure his time and the FDC’s time are synchronized prior to the mission.

Time to Target

2-149.  The observer may tell the FDC when he wants the rounds to impact by requesting TIME TO TARGET (so many) MINUTES AND SECONDS, OVER, STANDBY, READY, READY, HACK, OVER. Time to target is the time in minutes and seconds after the “hack” statement is delivered when rounds are expected to hit the target.

Check Firing

2-150.  CHECK FIRING is used to cause an immediate halt in firing. Use this command only when necessary to immediately stop firing (for example, safety reasons) as it may result in cannons being out of action until any rammed/loaded rounds can be fired or cleared from the tubes.


2-151.  REPEAT can be given during adjustment or fire-for-effect missions. During adjustment, REPEAT means firing another round(s) with the last data and adjusting for any change in ammunition if necessary. REPEAT is not sent in the initial call for fire.

2-152.  During fire for effect, REPEAT means fire the same number of rounds using the same method of fire for effect as last fired. Changes in the number of guns, the previous corrections, the interval, or the ammunition may be requested.

Request Splash

2-153.  SPLASH can be sent at the observer’s request. The FDC announces SPLASH to the observer 5 seconds prior to round impact. SPLASH must be sent to aerial observers and during high-angle fire missions.

Refinement and End of Mission

2-154.  The observer should observe the results of the fire for effect and then take one of the following actions to complete the mission:

– Correct any adjustments.

– Record as target.

– Report battle damage assessment.

– Report end of mission.

Adjust Fire

2-155.  If the rounds have accurately impacted the target after the initial call for fire, the observer requests fire for effect. If the rounds are not impacting the target, the observer adjusts the indirect fire onto the enemy target. Making adjustments to an indirect fire mission requires the observer to determine deviation and range corrections. Deviation corrections move the round right or left toward the target while range corrections add or drop the round toward the target with respect to the observer’s position. If the observer cannot locate the target (due to deceptive terrain, lack of identifiable terrain features, poor visibility, or an inaccurate map), he adjusts the impact point of the rounds. The observer chooses an adjusting point. For a destruction mission (precision fire), the target is the adjusting point. For an area target (area fire), the observer picks a well defined adjusting point close to the center. The observer spots the first and each successive adjusting round and sends range and deviation corrections back to the FDC until rounds hit the target. The observer spots each round by relating the round’s point of impact to the adjusting point. See FM 6-30, Tactics, Techniques, and Procedures for Observed Fire, for a more detailed discussion of adjusting mortar and artillery fire.

Deviation Spotting

2-156.  Deviation spotting (left or right) involves measuring the horizontal angle (in mils) between the actual burst and the adjusting point (Figure 2-14). For example, a burst to the right of the target is spotted as “(so many) mils right.” The observer uses an angle-measuring device to determine deviation. He might use the mil scale on his binoculars (Figure 2-15), or he might use his hand and fingers (Figure 2-16).


Figure 2-14. Deviation spotting.

Figure 2-15. Binocular reticle with mil scale.


Figure 2-16. Estimating deviation angles with your hand.

2-157.  On binoculars, the horizontal scale is divided into 10-mil increments and is used for measuring horizontal angles. The vertical scales in the center and on the left of the reticle (divided into 5-mil increments) are used for measuring vertical angles. The scale on the right, if present, is no longer used.

2-158.  A burst on the OT line is spotted as “line.” Deviation (left or right) should be measured to the nearest 5 mils for area targets, with measurements taken from the center of the burst. Deviation for a destruction mission (precision fire) is estimated to the nearest mil. Figure 2-17 shows the adjusting point at the center of the binocular horizontal scale.


Figure 2-17. Deviation spotting with binoculars.

Deviation Correction

2-159.  Deviation correction is the distance (in meters) the burst must be moved left or right to be on line between the observer and the target. Once the mil deviation has been determined, the observer converts it into a deviation correction (in meters). The OT distance is converted to a number called the OT factor (see FM 6-30). The OT factor is used in adjusting fires after the initial call for fire. The OT direction is usually determined in mils but degree azimuths can be used if necessary. OT distance is determined through individual range estimation or through the use of specific technical laser range-finding equipment (such as MELIOS). To determine the OT factor, take the range to the target, divide by 1,000, then round to the nearest even whole number.

2-160.  The deviation correction is determined by multiplying the observed deviation in mils by the distance from the observer to the target in thousands of meters (the OT factor). The result is expressed to the nearest 10 meters (Figure 2-18 [Example 1]).

2-161.  In adjustment of area fire, small deviation corrections (20 meters or less) can be ignored except when a small change determines a definite range spotting. Throughout the adjustment, the observer moves the adjusting rounds close enough to the OT line so range spotting is accurate. A minor deviation correction (10 to 20 meters) should be made in adjustment of precision fire.

2-162.  If the OT distance is greater than 1,000 meters, round to the nearest thousand and express it in thousands of meters (Figure 2-18 [Example 2]). If the OT distance is less than 1,000 meters, round to the nearest 100 meters and express it as a decimal in thousands of meters (Figure 2-18 [Example 3]).


Deviation Correction


Example 1:

      Observer deviation 20 mils

      OT distance 2,000 meters

      OT factor 2

      Observer deviation x OT factor = deviation correction

      20 x 2 = 40 meters


Example 2:

      OT distance 4,200 meters – OT factor 4

      OT distance 2,700 meters – OT factor 3


Example 3:

      OT distance 800 meters – OT factor 0.8

Figure 2-18. Determing deviation correction.

Angle T

2-163.   Angle T (Figure 2-19) is the angle formed by the intersection of the gun‑target line and the OT line with its vertex at the target. If angle T is 500 mils or greater, the FDC should tell the observer. If this occurs, the observer continues to use the OT factor to make his deviation corrections. If he sees that he is getting more of a correction than he has asked for, the observer should consider cutting the corrections in half to better adjust rounds onto the target.


Figure 2-19. Angle T.

Range Spotting

2-164.  Range spotting (short or over) requires adjusting the range to obtain fire on the target. An adjusting round’s burst on or near the OT line gives a definite range spotting. If he cannot make a definite spotting, the observer announces a “lost” or “doubtful” spotting. In these situations only, he gives the deviation correction to the FDC. Deviation corrections include—

– Over. The observer sees the burst beyond the adjusting point.

– Short. The observer sees the burst between himself and the adjusting point.

– Target. The observer sees the burst hit the target. He uses this spotting only in precision fire (destruction missions).

– Range Correct. The observer believes that the burst occurred at the correct range.

– Doubtful. The observer sees the burst but cannot tell whether it occurred over, short, target, or range correct.

– Lost, The observer cannot see or hear the burst.

Range Correction

2-165.  With each successive correction, the adjusting round lands over or short of the adjusting point, but closes on the target. There are three methods of range corrections: successive bracketing; hasty bracketing; and the creeping method.

Successive Bracketing

2-166.  In bracketing, the observer deliberately gives range corrections that land over or short of the target.  After spotting the first round, the observer makes a drop/add correction which he believes will give him one round over and one round short of the target.  For example, if the first round impacts over the target, the observer will give a drop correction which is large enough to cause the next round to impact short of the target.  Once the observer meets the goal of one round over and one round shot, he cuts each correction in half and drops or adds as necessary. The observer continues bracketing until his correction is less than 50 meters. At this point his adjustment is finished and he transitions to a fire-for-effect mission. Using the above example, his final adjustment would be “add 50 meters fire for effect.” This technique is called successive bracketing (Figure 2-20).

2-167.  When bracketing, the observer uses the following guide to determine his first range correction:

l     OT distance between 1,000 to 2,000 meters – initial add or drop at least 200 meters (+/- 200, +/- 100, +/- 50 fire for effect).

l      OT distance greater than 2,000 meters – initial add or drop at least 400 meters (+/- 400, +/-
200, +/- 100, +/- 50 fire for effect).


Figure 2-20. Successive bracketing technique.

Hasty Bracketing

2-168.  An alternative to successive bracketing is hasty bracketing. Bracketing is an effective technique in that it is sure to bring fire on the target. However, bracketing is relatively time consuming. If the target is moving, bracketing may not be fast enough to engage the target.

2-169.  A successful hasty bracket depends on a thorough terrain analysis, which gives the observer an accurate initial target location. For his first correction, the observer receives a bracket similar to that used for successive bracketing. Once the observer receives the initial bracket, he uses it like a yardstick to determine the subsequent correction. He then sends the FDC the correction to move the rounds to the target and to fire for effect (Figure 2-21). Hasty bracketing improves with observer experience and judgment.


Figure 2-21. Hasty bracketing technique.

Creeping Method

2-170.  In danger close situations, the observer uses the creeping method of adjustment. He calls for the first round and deliberately overshoots the target. He adjusts rounds in 100-meter increments or less until the fire hits the target (Figure 2-22). This method requires more time and ammunition than other methods. Therefore, the observer uses it only when he must consider safety first.


Figure 2-22. Creeping method of adjustment.

End of mission

2-171.  End of mission completes the mission and reports the battle damage assessment. The report should go to both the FDC and parent unit. Higher headquarters staff officers use battle damage assessment to update their staff estimates and feed the common operating picture. The proper report format for an indirect fire mission is END OF MISSION, TARGET# ____, BDA, OVER. An example of battle damage assessment is FOUR T72s DESTROYED, or ENEMY SNIPER TEAM SUPPRESSED.

fire support coordination measures

2-172.  Leaders use fire support coordination measures (FSCM) to facilitate both the engagement of targets and protection of friendly forces. Boundaries are the most basic FSCM. Boundaries are both permissive and restrictive FSCM. The fire support coordinator recommends FSCM to the leader based on the leader’s guidance, location of friendly forces, scheme of maneuver, and anticipated enemy actions. Once the leader establishes FSCM, they are entered into or posted on all the unit’s displays and databases (see FM 1-02).

Permissive FSCM

2-173.  The primary purpose of permissive measures is to facilitate the attack of targets. Once they are established, further coordination is not required to engage targets affected by the measures. Permissive FSCM include a coordinated fire line, fire support coordination line, and free-fire area.

Coordinated Fire Line

2-174.  A coordinated fire line (CFL) is a line beyond which conventional, direct, and indirect surface fire support means may fire at any time within the boundaries of the establishing headquarters. This is done without additional coordination. The purpose of the CFL is to expedite the surface-to-surface attack of targets beyond the CFL without coordination with the ground commander in whose area the targets are located (see JP 3-09, Joint Fire Support). Brigades or divisions usually establish a CFL, though a maneuver battalion may establish one. It is located as close as possible to the establishing unit without interfering with maneuver forces to open up the area beyond to fire support.

Fire Support Coordination Line

2-175.  The fire support coordination line (FSCL) is an FSCM that facilitates the expeditious attack of surface targets of opportunity beyond the coordinating measure. The FSCL applies to all fires of air-, land-, and sea-based weapon systems using any type of ammunition. Forces attacking targets beyond an FSCL must inform all affected commanders in sufficient time to allow necessary reaction to avoid fratricide. Supporting elements attacking targets beyond the FSCL must ensure that the attack will not produce adverse effects on or to the rear of the line. Short of an FSCL, all air-to-ground and surface-to-surface attack operations are controlled by the appropriate leader responsible for that area.

Free-Fire Area

2-176.  A free-fire area is a specific area into which any weapon system may fire without additional coordination with the establishing headquarters. Normally, division or higher headquarters establish a free-fire area on identifiable terrain.

Restrictive FSCM

2-177.  A restrictive FSCM prevents fires into or beyond the control measure without detailed coordination. The primary purpose of restrictive measures is to provide safeguards for friendly forces. Restrictive FSCM include no-fire area, restrictive fire area, and restrictive fire line.

No-Fire Area

2-178.  A no-fire area (NFA) is a land area designated by the appropriate commander into which fires or their effects are prohibited. Leaders use the NFA to protect independently-operating elements such as forward observers and special operating forces. They also use it for humanitarian reasons such as preventing the inadvertent engagement of displaced civilian concentrations, or to protect sensitive areas such as cultural monuments. There are two exceptions to this rule:

(1)     The establishing headquarters may approve fires within the NFA on a case-by-case mission basis.

(2)     When an enemy force within an NFA engages a friendly force, the friendly force may engage a positively-identified enemy force to defend itself.

Restrictive Fire Area

2-179.  A restrictive fire area (RFA) is an area in which specific restrictions are imposed and into which fires that exceed those restrictions will not be delivered without coordination with the establishing headquarters. The purpose of the RFA is to regulate fires into an area according to the stated restrictions such as no unguided conventional or dud-producing munitions. For example, no DPICM rounds should be fired into an area of land that is later going to be occupied by friendly forces. These types of munition have a dud rate and could possibly result in friendly forces being incapacitated. Maneuver battalion or larger ground forces normally establish RFAs. On occasion, a company operating independently may establish an RFA. An RFA is usually located on identifiable terrain by grid or by a radius (in meters) from a center point. The restrictions on an RFA may be shown on a map or overlay, or reference can be made to an operation order that contains the restrictions.

Restrictive Fire Line

2-180.  A restrictive fire line is a phase line established between converging friendly forces that prohibits fires or their effects across that line. The purpose of this phase line is to prevent fratricide between converging friendly forces. The next higher common commander of the converging forces establishes the restrictive fire line. Alternatively, the commander can use a restrictive fire line to protect sensitive areas such as cultural monuments. This control measure can also be used as a direct fire control measure.

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