Infantry Drills

FM 3-21.8 – Appendix C – Fire Planning

Appendix C

Fire Planning

Fire planning is the continual process of selecting targets on which fires are prearranged to support a phase of the concept of operation.  Fire planning is accomplished concurrently with maneuver planning at all levels. Leaders conduct fire planning to suppress, isolate, obscure, neutralize, destroy, deceive, or disrupt known, likely, or suspected targets, and to support the actions of the maneuver element.  Fires are planned for all phases of an operation.

 

section i —  fire planning

C-1.       Fire planning starts as soon as the leader gets a mission. Once begun, fire planning continues through the operation’s completion.  The primary aim of fire planning is to develop how fire is to be massed, distributed and controlled to best support the leader’s concept of operation.

C-2.       Fires are either targets of opportunity, or planned targets.  Targets of opportunity are not planned in advance, but are engaged as they present themselves in accordance with established engagement criteria and rules of engagement.  Planned targets are ones on which fires are prearranged, although the degree of this prearrangement may vary. The degree of prearrangement influences the time it takes to receive fires. The greater the prearrangement—the faster the reaction time. The subject of this section is planned fires.

C-3.       Planned targets are categorized as scheduled, or on-call.  Scheduled fires are fired in accordance with a pre-established time schedule and sequence. On-call targets are fired in response to a request for fires.  Priority targets are a special type of on-call target. Priority targets have quick reaction times because the firing unit has guns set on a specific target when not engaged in other fire missions.

C-4.         To be effective fires must be integrated and synchronized in time, space, and purpose over the entire concept of operation.  Integration means all available assets are planned and used throughout an operation. Synchronization means that these assets are sequenced in time, space, and purpose in an optimal manner, producing complementary and reinforcing effects for the maneuver element.

 

              On 14 May 1945 during the Ryukyus Campaign in Okinawa after three days of heavy fighting, the companies of 1stBattalion, 305th IN, 77th ID were reduced to the size of platoons, led by corporals and sergeants.  Despite loses, the commander decided to continue its advance. In order to achieve surprise, the morning attack began without preparatory fires.  The rifle companies moved over the LD at 0800 hours and advanced 200 yards with out a shot being fired by the enemy.  Surprise had been achieved, but the enemy quickly recovered and achieved fire superiority by pouring machine gun and mortar fire on the attacking units, stopping their advance.  Two of the enemy positions along ridge were destroyed by mortar fire but the troops were still unable to move with out being met by enemy fire.  Determined not to loose ground already gained, the battalion commander ordered the 81-mm mortar platoon to place suppressive fires in front of the lead company.  Placing fire only 50 yards in front of the troops, he kept moving the barrage ahead as troops advanced.

              The battalion’s mortar PL went forward to the lead elements, and after a hasty visual recon decided to use two mortars on the mission.  He adjusted one mortar about 50 yards in front of the company and the second about 100 yards in front of the company. One fired at a range of 700; the other at a range of 750 yards.  At these ranges two turns of the elevating crank would move the impact of the round about 25 yards.

              The lead company slowly resumed its advance, moving behind this curtain of mortar fire.  The enemy moved back into their cave positions to get out of the fire, becoming easy prey for flame throwers and satchel charges.  Seven caves were taken care of in this fashion as the advance moved slowly – but continuously forward.  Each mortar fired at a rate of about 10 rounds per minute.  Some rounds fell as close as 25 yards to the troops, wounding three riflemen with fragments.  Within 45 minutes ridge 59 was secured.

—Suppressive Fires

Fire Planning Process

C-5.       Fire planning begins with the concept of fires.  This essential component of the concept of operation complements the leader’s scheme of maneuver detailing the leader’s plan for direct and indirect preparatory and supporting fires.  Fire planning requires a detailed knowledge of weapon characteristics and logistical capabilities of those providing the support.  Although leaders may be augmented with personnel to assist in planning and controlling attached or supporting assets, the responsibility for planning and execution of fires lies with the leader. The leaders do not wait to receive the higher headquarters’ plan to begin their own fire planning. Rather, he begins as soon as possible to integrate fires into his own concept of operation and the concept of operation of the higher headquarters.

C-6.       Additional assets are allocated in either a command or support relationship (see Chapter 1).  An example of a command relationship would be an attachment of a section from the weapons company.  The leader relies on the senior representative from the organization to provide expertise when planning.  An example of a support relationship would be direct support from the artillery battalion or from an attack aviation company. When planning fires or CAS from a supporting unit, the leader normally receives someone from that organization to assist them.  For example, if the unit were to get close air support (CAS), a Soldier trained to control the CAS would probably be attached to assist the leader in his planning and execution.

C-7.       Developing the concept of fire should be fairly straight forward during deliberate operations because of the ability to conduct reconnaissance, planning, and preparation.  However, during hasty operations the unit may have to rely on its internal SOPs and more hands on control by the leader.

PLOT-CR

C-8.       Leaders refine, or establish if required, timings and control to ensure these targets are initiated, adjusted, and shifted properly. If possible, the observer should locate where he can see assigned target.  Leaders refine, or develop a detailed execution matrix assigning responsibility for each target to the leader or observer who is in the best position to control them should be developed. These Soldiers must know when each target, series, or group is fired. They must also understand what effect is desired on which enemy positions, and when to lift or shift the fires. Leaders may consider the use of pyrotechnic or other signals to ensure communication.  Units’ assigned responsibilities for executing fires continually refine and rehearse their actions.  Responsibilities are further refined with the information contained in the categories contained in the memory aid PLOT:

Purpose

C-9.       The purpose outlines how the target assists the maneuver element or contributes to the higher headquarters’ concept of operation.

Location

C-10.    An identified target is the target’s proposed location given as a grid preferably with a known point.  The target location is not the location of the enemy – it is where the leader (or the higher headquarters) thinks the enemy will be.

Observer

C-11.  The observation plan is how the leader plans to monitor the battlefield to execute the target.  He assigns primary and alternate observers with proposed locations where they can observe the target and associated triggers.  Positioning is perhaps the most important aspect of the plan.  Observers’ positions must allow them to see the trigger for initiating fires as well as the target area and the enemy forces on which the target is oriented. The leader also must consider other aspects of observer capabilities, including available equipment, communication, and their security. This information is critical to the leader. If an enemy asset is critical enough to be designated as a target, then it must be adequately resourced with execution assets.

Trigger

C-12.    A trigger is event- or time-oriented criteria used to initiate planned actions directed toward achieving surprise and inflicting maximum destruction on the enemy or a designated point (FM 1-02).  Triggers can be a physical point on the ground, a laser or lazed spot, or an action or event that causes and action among friendly forces.  When using triggers to control fires, leaders ensure they have allocated them to start, shift, and cease fires. There are two types of triggers: tactical; and technical. Tactical triggers cue the observer/ executor of the target to communicate to the firing agency to prepare to fire.  In the offense tactical triggers are tied to a friendly maneuver event.  In the defense, tactical triggers are usually tied to enemy actions.  Technical triggers involve the actual firing of the target, taking into account the enemy rate of march, and the friendly munition’s time of flight.

C-13.    When using triggers in the defense it is important for subordinates to have a method, usually addressed in the unit’s SOP, for marking triggers.  The marking method should work during day and limited visibility operations.

Tactical uses of planned Fires

C-14.    Fires are used for many different tactical reasons.  They include:

– Fire delivered before an attack to weaken the enemy position (FM 1-02).

– Supporting fires (covering fires). Supporting fires enable the friendly maneuver element to move by destroying, neutralizing, or suppressing enemy fires, positions, and observers.

– Final protection fires (FPF) is an immediately available prearranged barrier of fire designed to impede enemy movement across defensive lines or areas.

– Suppression.

– Obscuration.

– Counterbattery (indirect fires only).  Counterbattery is fire to destroy or neutralize enemy artillery / mortars.  These missions are normally controlled at higher level headquarters.  Direct support artillery moves with supported units and aviation is used to destroy enemy fire support means and key enemy units and facilities.  Counter battery radars are positioned to maintain radar coverage to ensure continuous coverage during rapid movement forward.

– Harassing fire is observed or predicted (unobserved) fire intended to disrupt enemy troop and vehicle movement, disturb their rest, and lower their morale.

– Illumination.

Echelonment of Fire – Planned Fires Technique

C-15.     Echelonment of fires is the schedule of fire ranging from the highest caliber munitions to the lowest caliber munitions.  The purpose of echeloning fires is to maintain constant fires on the enemy while using the optimum delivery system.  Leaders use REDs, SDZs, and MSDs to manage associated risks.  In the defense, triggers are tied to the progress of the enemy as it moves through the AO, enabling the leader to engage the enemy throughout the depth of the sector.  In the offense triggers are tied to the progress of the maneuver element as it moves toward the objective protecting the force and facilitating momentum up to the objective.

Defensive Echelonment

C-16.    In the defense, echeloning fires are scheduled based on their optimum ranges to maintain continuous fires on the enemy, disrupting his formation and maneuver.  Echelonment of fires in the defense places the enemy under increasing volumes of fire as he approaches a defensive position.  Aircraft and long-range indirect fire rockets and artillery deliver deep supporting fires. Close supporting fires such as final protective fires (FPF) are closely integrated with direct fire weapons such as Infantry weapons, tank support, and antiarmor weapons systems. Figure C-1 illustrates an example of defensive echelonment.

Figure C-1. Defensive echelonment of fires example.

Offensive Echelonment

C-17.    In the offense, weapons are scheduled based on the point of a predetermined safe distance away from any maneuvering friendly troops. When scheduled effectively, fires provide protection for friendly forces as they move to and assault an objective. They also allow friendly forces to get in close with minimal casualties and prevent the defending enemy from observing and engaging the assault by forcing him to take cover.  The overall objective of offensive scheduled fires is to allow the friendly force to continue the advance unimpeded (Figure C-2).

Figure C-2. Offensive echelonment of fires example.

C-18.    As an example of echelonment of fires use during the conduct of a mission, consider an operation in which a platoon assaults an enemy position (Figures C-3 through C-6). As the lead elements of the unit approach the designated phase line en route to the objective, the leader orders the fire support officer (FSO) to begin the preparation. Observers track friendly movement rates and confirm them. Other fire support officers in the chain of command may need to adjust the plan during execution based on unforeseen changes to anticipated friendly movement rates.

C-19.    As the unit continues its movement toward the objective, the first weapon system engages its targets. It maintains fires on the targets until the unit crosses the next phase line that corresponds to the RED of the weapon system being fired.

C-20.    To maintain constant fires on the targets, the next weapon system begins firing before the previous weapon system ceases or shifts. This ensures no break in fires, enabling the friendly forces’ approach to continue unimpeded. However, if the unit rate of march changes, the fire support system must remain flexible to the changes.

C-21.    The FSO shifts and engages with each delivery system at the prescribed triggers, initiating the fires from the system with the largest RED to the smallest. Once the maneuver element reaches the final phase line, the FSO ceases the final indirect fire system or shifts to targets beyond the objective to cease all fires on the objective. Direct fire assets in the form of supporting fires are also maintained until the final assault, then ceased or shifted to targets beyond the objective.

 

Figure C-3. 81-mm mortars begin firing.

 

Figure C-4. 81-mm mortars shift, 60-mm mortars and supporting fires begin.

 

Figure C-5. 60-mm mortars shift.

 

Figure C-6. Supporting fires shift for final assault.


Fire Planning for the Defense

C-22.    To develop a defensive fire plan, the leader—

– Assigns primary and secondary sectors from primary and alternate position to each subordinate.

– Designates unit point or area targets and other control measures, such as target reference points (TRPs), to coordinate the fire when more than one subordinate is firing into the same engagement area or sector.

– Receives target information from subordinates (normally provided on sector sketches and/or individual weapon range cards). The leader reviews this target information to insure that fire is equally distributed across the entire unit’s sector and that sufficient control measures are established.

– Completes the unit’s fire plan and gives a sketch to his higher headquarters.

C-23.    In the defense, fires are planned in three locations – in front of the unit’s position, on the position (FPF), and behind the position.  Figure C-7 shows fires masses in front of a company-sized position.  Fire plans are best developed using the seven steps of engagement area development technique:

(1) Identify likely enemy avenues of approach.

(2) Identify the enemy scheme of maneuver.

(3) Determine where to kill the enemy.

(4) Emplace weapon systems.

(5) Plan and integrate obstacles.

(6) Plan and integrate indirect fires.

(7) Conduct an engagement area rehearsal.

Figure C-7. Company defensive fire plan sketch.

 

C-24.    The engagement area (EA) is the place where the leader intends to destroy an enemy force using the massed fires of all available weapons. The success of any engagement depends on how effectively the leader can integrate the obstacle and indirect fire plans with his direct fire plan in the EA to achieve the unit’s purpose. Completing the steps of EA development is not a lengthy process.  Particularly at the Infantry platoon level, EA development can occur rapidly without an elaborate decision making process.

Squad fire planning

C-25.     The squad leaders make two copies of their sector sketches. One copy goes to the platoon leader; the other remains at the position. The squad leaders draw sector sketches as close to scale as possible, showing the elements contained in Figure C-8.

Figure C-8. Squad sector sketch.

Platoon Fire Planning

C-26.    Squad leaders prepare their sketches and submit them to the platoon leader. The platoon leader combines all sector sketches (and possibly separate range cards) to prepare a platoon sector sketch. A platoon sector sketch is drawn as close to scale as possible that includes a target list for direct and indirect fires. One copy is submitted to the company commander, one copy is given to the PSG, and one copy is maintained by the platoon leader. As a minimum, the platoon sector sketch should show the elements contained in Figure C-9.

 

Figure C-9. Platoon sector sketch.

Final Protective Line

C-27.    The final protective line (FPL) is a line of fire selected where an enemy assault is to be checked by interlocking fire from all available weapons and obstacles (FM 1-02). The FPL consists of all available measures, to include protective obstacles, direct fires, and indirect fires.  The FPF targets the highest type of priority targets and takes precedence over all other fire targets. The FPF differs from a standard priority target in that fire is conducted at the maximum rate until the mortars are ordered to stop, or until ammunition is depleted.  If possible, the FPF should be registered.

C-28.    If Soldiers are in well-prepared defensive positions with overhead cover, an FPF can be adjusted very close to the friendly positions, just beyond bursting range. If required, the leader can even call for artillery fires right on the unit’s position using proximity or time fuzes for airbursts.  Table C-1 shows indirect fire mortar weapon system characteristics that should be used when planning the FPF.

 

Table C-1. Normal FPF dimensions for each number of mortars.

Weapon

Number  of Tubes

Width (meters)

Depth (meters)

Risk Estimated Distance, .1% PI

Risk Estimated Distance, 10% PI

 

MORTARS

 

120 mm 4 300 75

400m

100m

 
120 mm 2 150 75  
81 mm 4 150 50

230m

80m

 
81 mm 2 75 50  
60 mm 2 60 30

175m

65m

 

Fire Planning for the Offense

C-29.    Offensive fire planning follows the same methodology as defensive fire planning within constraints of the situation.  The main difference is that offensive fire planning always includes the synchronization between the base of fire and the maneuver element.  Inevitably, the leader’s plan will not be as detailed as the defensive plan, but the presence of a maneuver element requires a baseline of planning and control to ensure fire support is effective and efficient.

C-30.    The leader must plan how he will engage known or suspected enemy targets, where friendly suppressive fire may be needed, and how he will control the unit’s fires against both planned targets and targets of opportunity. Fire planning should include a thorough analysis of the type of threat expected. This will aid the supporting friendly element in tailoring the weapon and ammunition requirements to suit the situation.

C-31.    Offensive fire planning supports four phases: planning and preparation, approach to the objective, actions on the objective, and follow-through.  The degree of completeness and centralization of offensive fire planning depends on the time available to prepare for the offensive.  Fires are planned in four locations on the battlefield – short of the LD / LC, LD / LC to the objective, on the objective, and behind the objective. Table C-2 lists planning considerations for each of the four locations.

Table C-2. Planning considerations.

Phase

Plan Fires to:

1) Planning and Preparation (Short of the LD / LC)

·         Support unit in assembly areas.

·         Support unit’s movement to the LD / LC.

·         Disrupt enemy reconnaissance forces.

·         Disrupt enemy defensive preparations.

·         Disrupt enemy spoiling attacks.

 

2) Approach to the Objective (LD / LC to the Objective)

·         Begin echeloning fires for maneuver units.

·         Suppress and obscure for friendly breaching operations.

·         Suppress and obscure enemy security forces throughout movement.

·         Provide priority of fires to lead element.

·         Screen / guard exposed flanks.

 

3) Actions on the Objective (On the Objective)

·         Fires to block enemy reinforcements.

·         Fires to suppress enemy direct fire weapons.

·         Suppress and obscure point of penetration.

·         Suppress and obscure enemy observation of friendly forces.

 

4) Follow Through

(Beyond The Objective)

·         Disrupt movement of enemy reinforcements during the assault.

·         Block avenues of enemy approach.

·         Disrupt enemy withdraw.

·         Screen friendly forces from enemy counterattacks during the assault.

·         Consolidate objective after the assault.

 

C-32.    For simplicities, offensive fire planning is divided into two categories – preparatory and supporting fires.  The concept of fires will have artillery and mortars in support of an attack to gain and maintain fire superiority on the objective until the last possible moment. When this indirect fire lifts, the enemy should be stunned and ineffective for a few moments. Take full advantage of this period by doing any or all of the following:

– Combat Vehicles. Vehicles used in the attack, or as fire support, continue to give close support.

– Maintaining Fire Superiority.  Small-arms fire from local and internal SBF is continued as long as possible.

– Maneuver Elements.  Assaulting troops must try to fire as they advance.  Troops must observe fire discipline, as in many cases fire control orders will not be possible. They must not arrive at the objective without ammunition.

– Audacity.  Where the ground and vegetation do not prohibit movement, leading sections should move very quickly over the last 30 or 40m to the enemy positions to minimize exposure.

C-33.    When planning fires for the offense, leaders verify the fire element’s task organization and ensure there exists plans and coordinating measures for the attack, exploitation, pursuit, and contingency plans.  Leaders develop or confirm with the responsible level authority that supporting systems are positioned and repositioned to ensure continuous fires throughout the operation.  Mutual support of fire systems promotes responsive support and provides the commanders of maneuver units freedom of action during each critical event of the engagement or battle

C-34.    There exists a diverse variety of munitions and weapon systems, direct and indirect, to support close offensive operations.  To effectively integrate fire support, the leader must understand the mission, the commander’s intent, the concept of operations, and the critical tasks to be accomplished.  The leader plans fires to focus on enemy capabilities and systems that must be neutralized.  Critical tasks include:

– Continuous in-depth support (accomplished by proper positioning of systems).

– Isolating enemy forces.

– Softening enemy defenses by delivering effective preparatory fires.

– Suppressing and obscuring enemy weapon systems to reduce enemy standoff capabilities.

– Interdicting enemy counterattack forces, isolating the defending force, and preventing its reinforcement and resupply.

 

section ii — target effects planning

C-35.    Not only must fire support planners determine what enemy targets to hit, and when, but must also decide how to attack each enemy target. Leaders should consider all the aspects of target effects when planning fires. Although this section is specific to mortars, the following concepts generally apply to most indirect fires.

HIGH-EXPLOSIVE AMMUNITION

C-36.    When mortar rounds impact they throw fragments in a pattern that is never truly circular, and may even travel irregular, based on the round’s angle of fall, the slope of the terrain, and the type soil. However, for planning purposes, each mortar high explosive (HE) round is considered to have a circular lethal bursting area. Figure C-10 shows a scale representation of the lethal bursting areas of mortar rounds.

 

Figure C-10. Comparison of lethal bursting areas of U.S. mortar rounds.

FUZE SETTINGS

C-37.    The decision concerning what fuze setting to use depends on the position of the enemy.

C-38.    Exposed enemy troops that are standing up are best engaged with impact (IMP) or near surface burst (NSB) fuze settings. The round explodes on, or near, the ground.  Shell fragments travel outward perpendicular to the long axis of the standing target (Figure C-11).

Figure C-11. Standing targets.

C-39.    If exposed enemy troops are lying prone, the proximity (PRX) fuze setting is most effective. The rounds explode high above the ground, and the fragments coming downward are once again traveling perpendicular to the long axis of the targets (Figure C-12).

 

Figure C-12. Prone targets.

C-40.    The PRX setting is also the most effective if the enemy is in open fighting positions, without overhead cover. Even PRX settings will not always produce effects if the positions are deep (Figure C-13).

 

Figure C-13. Targets in open fighting positions.

C-41.    The DLY fuze setting is most effective when the enemy is below triple canopy jungle or in fighting positions with overhead cover.  Light mortars will have little effect against overhead cover. Even medium mortars have limited effect. Heavy mortars can destroy a bunker or enemy troops beneath jungle canopy with a hit or near-miss (Figure C-14).

 

Figure C-14. Targets beneath triple canopy jungle.

EFFECTS OF COVER ON HIGH-EXPLOSIVE ROUNDS

C-42.    Enemy forces will normally be either standing or prone. They maybe in the open or protected by varying degrees of cover. Each of these changes the target effects of mortar fire.

C-43.    Surprise mortar fire is always more effective than fire against an enemy that is warned and seeks cover. Recent studies have shown that a high casualty rate can be achieved with only two rounds against an enemy platoon standing in the open. The same studies required 10 to 15 rounds to duplicate the casualty rate when the platoon was warned by adjusting rounds and sought cover. If the enemy soldiers merely lay prone, they significantly reduce the effects of mortar fire. Mortar fire against standing enemy forces is almost twice as effective as fire against prone targets.

C-44.    Proximity fire is usually more effective than surface-burst rounds against targets in the open. The effectiveness of mortar fire against a prone enemy is increased by about 40 percent by firing proximity-fuzed rounds rather than surface-burst rounds.

C-45.    If the enemy is in open fighting positions without overhead cover, proximity-fuzed mortar rounds are about five times as effective as impact-fuzed rounds. When fired against troops in open fighting positions, proximity-fuzed rounds are only 10 percent as effective as they would be against an enemy in the open. For the greatest effectiveness against troops in open fighting positions, the charge with the lowest angle of fall should be chosen. It produces almost two times as much effect as the same round falling with the steepest angle.

C-46.    If the enemy has prepared fighting positions with overhead cover, only impact-fuzed and delay-fuzed rounds will have much effect. Proximity-fuzed rounds can restrict the enemy’s ability to move from position to position, but they will cause few, if any, casualties. Impact-fuzed rounds cause some blast and suppressive effect. Delay-fuzed rounds can penetrate and destroy a position but must achieve a direct hit. Only the 120-mm mortar with a delay-fuze setting can damage a Soviet-style strongpoint defense. Heavy bunkers cannot be destroyed by light or medium mortar rounds.

SUPPRESSIVE EFFECTS OF HE MORTAR ROUNDS

C-47.    Suppression from mortar is not as easy to measure as the target effect. It is the psychological effect produced in the mind of the enemy that prevents him from returning fire or carrying on his duties. Inexperienced or surprised Soldiers are more easily suppressed than experienced, warned Soldiers. Soldiers in the open are much more easily suppressed than those with overhead cover. Suppression is most effective when mortar fires first fall; as they continue, their suppressive effects lessen. HE rounds are the most suppressive, but bursting WP mixed with HE has a great psychological effect on the enemy.

C-48.    If a 60-mm mortar round lands within 20 meters of a target, the target will probably be suppressed, if not hit.

C-49.    If a 60-mm mortar round lands within 35 meters of a target, there is a 50 percent chance it will be suppressed. Beyond 50 meters, little suppression takes place.

C-50.    If an 81-mm mortar round lands within 30 meters of a target, the target will probably be suppressed, if not hit.

C-51.    If an 81-mm mortar round lands within 75 meters of a target, there is a 50 percent chance that the target will be suppressed. Beyond 125 meters, little suppression takes place.

C-52.    If a heavy mortar round (proximity-fuzed) lands within 65 meters of target, the target will probably be suppressed, if not hit.

C-53.    If a heavy mortar round (proximity-fuzed) lands within 125 meters of a target, there is a 50 percent chance the target will be suppressed.  Beyond 200 meters, little suppression takes place. The 120-mm mortar round is better for suppression than the 107-mm, but both are excellent suppressive rounds.

ILLUMINATION, SMOKE, AND WHITE PHOSPHORUS

C-54.    Illumination and obscuration missions are important functions for mortar platoons or sections. Atmospheric stability, wind velocity, and wind direction are the most important factors when planning target effects for smoke and white phosphorus (WP) mortar rounds. The terrain in the target area also effects smoke and WP rounds.

C-55.    The bursting WP round provides a screening, incendiary, marking, and casualty-producing effect. It produces a localized, instantaneous smoke cloud by scattering burning WP particles.

C-56.    The WP round is used mainly to produce immediate, close point obscuration. It can be used to screen the enemy’s field of fire for short periods, which allows troops to maneuver against him. The 60-mm WP round is not sufficient to produce a long-lasting, wide-area smoke screen, but the much larger WP round from the heavy mortar is.

C-57.    The bursting WP round can be used to produce casualties among exposed enemy troops and to start fires. The casualty-producing radius of the WP round is much less than that of the HE round. Generally, more casualties can be produced by firing HE ammunition than by firing WP.  However, the WP burst causes a significant psychological effect, especially when used against exposed troops. A few WP mixed into a fire mission of HE rounds may increase the suppressive effect of the fire.

C-58.    The WP rounds can be used to mark targets, especially for attack by aircraft. Base-ejecting smoke rounds, such as the 81-mm M819 RP round, produce a dispersed smoke cloud, normally too indistinct for marking targets.

C-59.    The effects of atmospheric stability can determine whether mortar smoke is effective at all or, if effective, how much ammunition will be needed.

– During unstable conditions, mortar smoke and WP rounds are almost ineffective–the smoke does not spread but often climbs straight up and quickly dissipates.

– Under moderately unstable atmospheric conditions, base-ejecting smoke rounds are more effective than bursting WP rounds. The M819 RP round for the M252 mortar screens for over 2½ minutes.

– Under stable conditions, both RP and WP rounds are effective.

– The higher the humidity, the better the screening effects of mortar rounds.

C-60.    The M819 RP round loses up to 35 percent of its screening ability if the ground in the target area is covered with water or deep snow. During extremely cold and dry conditions over snow, up to four times the number of smoke rounds may be needed than expected to create an adequate screen. The higher the wind velocity, the more effective bursting WP rounds are, and the less effective burning smoke rounds become.

C-61.    If the terrain in the target area is swampy, rain-soaked, or snow-covered, then burning smoke rounds may not be effective. These rounds produce smoke by ejecting felt wedges soaked in red phosphorus. These wedges then burn on the ground, producing a dense, long-lasting cloud. If the wedges fall into mud, water, or snow, they can be extinguished.  Shallow water can reduce the smoke produced by these rounds by as much as 50 percent. Bursting WP rounds are affected little by the terrain in the target area, except that deep snow and cold temperatures can reduce the smoke cloud by about 25 percent.

C-62.    Although bursting WP rounds are not designed to cause casualties, the fragments of the shell casing and bits of burning WP can cause injuries. Burning smoke rounds do not cause casualties and have little suppressive effect.

ILLUMINATION

C-63.    Illumination rounds can be used to disclose enemy formations, to signal, or to mark targets. There are illumination rounds available for all mortars.

C-64.    The 60-mm illumination round available now is the standard cartridge, illuminating, M83A3. This round has a fixed time of delay between firing and start of the illumination. The illumination lasts for about 25 seconds, providing moderate light over a square kilometer.

C-65.    The 60-mm illumination round does not provide the same degree of illumination as do the rounds of he heavier mortars and field artillery.   However, it is sufficient for local, point illumination. The small size of the round can be an advantage where illumination is desired in an area but adjacent friendly forces to not want to be seen. The 60-mm illumination round can be used without degrading the night vision devices of adjacent units.

C-66.    The medium and heavy mortars can provide excellent illumination over wide areas. The 120-mm mortar illumination round provides one million candlepower for 60 seconds.

C-67.    The M203 40-mm grenade, as well as all mortars have the capability to deliver IR illumination rounds in addition to the more common white light.

SPECIAL ILLUMINATION TECHNIQUES

C-68.    Following are three special illumination techniques that mortars have effectively used.

C-69.    An illumination round fired extremely high over a general area will not always alert an enemy force that it is being observed. However, it will provide enough illumination to optimize the use of image intensification (starlight) scopes such as the AN/TVS-5 and the AN/TVS-4.

C-70.    An illumination round fired to burn on the ground will prevent observation beyond the flare into the shadow. This is one method of countering enemy use of image intensification devices. A friendly force could move behind the flare with greater security.

C-71.    An illumination round fired to burn on the ground can be used to mark targets during day or night. Illumination rounds have an advantage over WP as target markers during high winds. The smoke cloud from a WP round will quickly be blown downwind. The smoke from the burning illumination round will continue to originate from the same point, regardless of the wind.

CONSIDERATIONS WHEN USING THERMAL SIGHTS

C-72.    Although illumination rounds may aid target acquisition when friendly forces are using image intensification devices (such as night vision devices), this is not so when thermal sights are used. As the illumination flares burn out and land on the ground, they remain as a distinct hot spot seen through thermal sights for several minutes. This may cause confusion, especially if the flare canisters are between the enemy and the friendly forces. WP rounds can also cause these hot spots that can make target identification difficult for gunners using thermal sights (tanks, BFV, TOW, or Javelin).


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