Section 5 - Engagement Area - InfantryDrills.com

5-204. The engagement area is an area where the commander masses effects to contain and destroy an enemy force (FM 3-90). Contain is a tactical mission task in which a unit stops, holds, or surrounds an enemy force (FM 3-90). Destroy is a tactical mission task that physically renders an enemy force combat-ineffective until reconstituted (FM 3-90). The platoon leader uses natural and man-made obstacles to canalize the attacking force into an engagement area where they can be destroyed by direct and indirect fires. The key to success is the platoon leader’s ability to integrate the obstacles, fires and direct fires plans within the engagement area to achieve the Infantry platoon’s and squads’ tactical purposes. (See ATP 3-21.10 and ATP 3-21.20 for additional information.)

Key Engagement Considerations

5-205. Engagement criteria are protocols that specify those circumstances for initiating engagement with an enemy force (FM 3-90). Engagement criteria may be restrictive or permissive in nature. For example, the platoon leader may instruct a subordinate squad leader not to engage an approaching enemy unit until the enemy commits to an avenue of approach. The platoon leader establishes engagement criteria in the direct fire plan in conjunction with engagement priorities and other direct fire control measures to mass fires and control fire distribution.

5-206. Engagement priority identifies the order in which the unit engages enemy systems or functions (FM 3-90). The platoon leader assigns engagement priorities (see paragraph A-61) based on the type or level of threat at different ranges to match organic weapon system capabilities against enemy vulnerabilities. Engagement priorities are situationally dependent and used to distribute fires rapidly and effectively. Subordinate elements can have different engagement priorities but will normally engage the most dangerous targets first, followed by targets in-depth or specialized systems, such as engineer vehicles.

5-207. A target reference point is a predetermined point of reference, normally a permanent structure or terrain feature that can be used when describing a target location. (JP 3-09.3). The platoon may designate TRPs (see paragraph A-41) to define unit or individual sectors of fire and observation, usually within the engagement area. TRPs, along with trigger lines, designate the center of an area where the platoon leader plans to distribute or converge the fires of all weapons rapidly. TRPs allow leaders to distribute, shift, or focus fires throughout the width and depth of an engagement area: for instance, a squad sector distributes fires between TRP 1 and TRP 2. A machine gun PDF may be established using a TRP to focus their fires. A squad may shift fires by shifting from TRP 1 in their primary sector to TRP 3 in their secondary sector. Trigger lines, when added, serve as a method of control. Once designated, TRPs may also constitute indirect fire targets.

5-208. A trigger line is a phase line located on identifiable terrain used to initiate andmass fires into an engagement area at a predetermined range (FM 3-90). The platoonleader can designate one trigger line (see paragraph A-62) for all weapon systems orseparate trigger lines for each weapon or type of weapon system. The leader specifiesthe engagement criteria for a specific situation. The criteria may be either time- or event-driven, such as a certain number or certain types of vehicles to cross the trigger linebefore initiating engagement. The leader can use a time-based fires deliverymethodology or a geography-based fires delivery.

Engagement Area Development

5-209. Engagement area development is a complex function demanding parallel planning and preparation if the Infantry platoon and squad are to accomplish the tasks for which they are responsible. Despite this complexity, engagement area development resembles a drill, and the platoon leader and subordinate leaders use an orderly, standard set of procedures. The steps of engagement area development are not a rigid sequential process. Some steps may occur simultaneously to ensure the synergy of combined arms (asterisks [*] denote steps that occur simultaneously). The platoon leader integrates these steps within the TLP and the IPOE (see chapter 2 for additional information). Beginning with evaluation of mission variables of METT-TC (I), the development process—

Identifies likely enemy avenues of approach.
Determines most likely enemy COA.
Determines where to kill the enemy.
Positions subordinate forces and weapon systems.*
Plans and integrates obstacles.*
Plans and integrates fires.*
Rehearses the execution of operations in the engagement area.

Identify Likely Enemy Avenues Of Approach

5-210. This step begins during the IPOE (see paragraph 2-4) and creating the platoon graphic terrain analysis overlay (GTAO), see paragraph 2-67, that is similar to the modified combined obstacle overlay (MCOO) prepared by the battalion intelligence staff officer (S-2) (see paragraph 2-6). Identifying avenues of approach (see paragraph 5-1) is important because all COAs that involve maneuver depend on available avenues of approach. During defensive operations, it is important to identify avenues of approach that support threat offensive capabilities when identifying the most likely enemy COA. See paragraphs 2-63 to 2-66 for information on the classification of severely restricted terrain, restricted terrain, and unrestricted terrain, reference the MCOO. Results of IPOE are validated during leader’s reconnaissance and preparation of the defense.

Note. The primary analytic tools used to aid in determining the effects specific to terrain, are the MCOO and the terrain effects matrix. The company commander expands upon the products received from the battalion to further identify the enemy avenues of approach.

5-211. Avenues of approach consist of a series of mobility corridors (see paragraph 5-1) through which a maneuvering force must pass to reach its objective. (See figure 5-20 on page 5-74.) Avenues of approach must provide ease of movement and enough width for dispersion of a force large enough to affect the outcome of the operation significantly. Avenues of approach are developed by identifying, categorizing, and grouping mobility corridors and evaluating avenues of approach. Additional procedures and considerations when identifying the enemy’s likely avenues of approach include:

Conducting initial reconnaissance. If possible, do this from the enemy’s perspective along each avenue of approach into the AO or engagement area.
Identifying key terrain—is an identifiable characteristic whose seizure or retention affords a marked advantage to either combatant (ADP 3-90) and decisive terrain—key terrain whose seizure and retention is mandatory for successful mission accomplishment (ADP 3-90). This includes locations affording positions of advantage over the enemy, as well as natural obstacles and choke points restricting forward movement.
Determining which avenues provide cover and concealment for the enemy while allowing the enemy to maintain its tempo.
Determining what terrain, the enemy is likely to use to support each avenue.
Evaluating lateral routes adjoining each avenue of approach.

Figure 5-20. Likely enemy avenues of approach

Identify Most Likely Enemy Course Of Action

5-212. This step is completed after step 4 (determine threat COAs) of the IPOE process (see paragraph 2-4) identifies and describes threat COAs that can influence the platoon’s AO and area of interest. Outputs from the S-2 cell during step 4 includes situation templates (known as SITEMPs) and COA statements for each COA. Procedures and considerations in determining the enemy’s most likely COA (enemy scheme of maneuver) include:

Determining how the enemy will structure the attack.
Determining how the enemy will use reconnaissance and surveillance assets. Will the enemy attempt to infiltrate friendly positions?
Determining where and when the enemy will change formations and establish support by fire positions.
Determining where, when, and how the enemy will conduct the assault or breaching operations.
Determining where and when the enemy will commit follow-on forces.
Determining the enemy’s expected rates of movement.
Assessing the effects of enemy combat multipliers and anticipated locations/areas of employment.
Determining what reactions, the enemy is likely to have in response to projected friendly actions.

Determine Where To Kill The Enemy

5-213. Generally, leaders at the platoon level decide where to kill the enemy within an engagement area assigned by a higher headquarters; however, leaders at the platoon level must assess the best place to kill the enemy within the assigned AO by understanding the terrain effects and the enemy they will face.

5-214. An analysis of the terrain, enemy scheme of maneuver and avenues of approach enables the platoon leader to understand how the enemy will enter, and flow through the platoon’s AO. Within the engagement area (either assigned or identified) the platoon leader determines through this analysis where exactly to mass fires. For example, is it where the enemy stops to cross a stream; is it where the terrain forces the enemy to cross in front of the platoon laterally giving it a flank shot; is it where the platoon can fire at a point where it can achieve enfilade fires; or is a chokepoint where the platoon can drop a wire obstacle to create a place to mass fires on a stationary enemy? Only after this analysis can the platoon leader accurately identify the most advantageous places to concentrate fires within the engagement area and then identify TRPs to focus, distribute, and shift fires within those places.

5-215. The following steps apply in identifying and marking where the enemy engagement (see figure 5-21 on page 5-76) is to occur:

Identify TRPs matching the enemy’s scheme of maneuver allowing the Infantry platoon and squad to identify where it will engage enemy forces through the depth of the AO.
Identify and record the exact location of each TRP.
In marking TRPs, use thermal sights to ensure visibility at the appropriate range under varying conditions, including daylight and limited visibility (darkness, smoke, dust, or other obscurants).
Determine how many weapon systems will focus fires on each TRP to achieve the desired end state.
Determine which element will mass fires on each TRP.
Establish engagement areas around TRPs.
Develop the direct fire planning measures necessary to focus fires at each TRP.

Figure 5-21. Locations to kill enemy

Position Subordinate Forces And Weapon Systems

5-216. The platoon leader does not normally position subordinate forces and weapon systems before completing steps 1, 2, and 3 of engagement area development. With an understanding of how the enemy will move through the engagement area, the optimal places to kill enemy forces within the engagement area, and tentative TRPs designated, the platoon leader plans where to emplace machine guns, antitank (AT) missiles, and squad battle positions to most effectively cover those places with direct fires. The platoon leader plans the use of primary and secondary sectors of fire, primary and alternate, subsequent and supplementary battle positions, and direct fire control measures to enable the platoon to focus, shift, and distribute direct fires throughout the EA. Additionally, emplacement of forces and weapon systems needs to support the desired obstacle effect to maximize the effectiveness of the engagement area. The following steps apply in selecting and improving battle positions and emplacing the Infantry platoon and squads, antiarmor weapon systems, crew-served weapon systems, vehicles (when attached), and individual fighting positions (see figure 5-22 on page 5-78):

Position key weapons systems first; ensure they can observe likely target locations.
Select tentative platoon/squad battle positions capable of massing fires in likely target locations; ensure they can observe tentative TRPs from the prone position.

Note. When possible, select battle positions while moving in the engagement area. Using the enemy’s perspective enables the Infantry leader to assess survivability of positions.

Conduct a leader’s reconnaissance of tentative battle positions.
Move along the avenue of approach into the engagement area (when possible) to confirm selected positions are tactically advantageous.
Confirm and mark the selected battle positions.
Ensure battle positions do not conflict with those of adjacent units and are tied in with adjacent positions.
Select primary, alternate, and supplementary fighting positions to achieve the desired effect for each TRP.
Ensure leaders position weapon systems so each TRP is covered by the required number of weapon systems and squads.
Stake weapons system positions and vehicles (when attached) according to unit SOPs so engineers can dig in the positions.
Confirm all weapons system positions.
When established, mark and rehearse route(s) and trigger(s) for the defending force to move from its hide position(s) (concealed from enemy observation) to its OP(s) and/or battle position(s).

Figure 5-22. Position subordinate forces and weapon systems

Plan And Integrate Obstacles

5-217. The platoon leader, as directed by the company commander, with the assistance of the engineer leader (when attached) determine an obstacle’s intent relative to its location, and effect to block, disrupt, fix, or turn attacking enemy forces into planned engagement areas. Countermobility planning includes the positioning of protective obstacles to prevent the enemy from closing with defensive battle positions, and integrating mines, wire, indirect fires, and direct fires in conjunction with placement.

The following apply in planning and integrating obstacles (see figure 5-23 on page 5-80) during defensive missions:

Platoon leader must understand what obstacle effort the platoon has been tasked to emplace by higher headquarters, whether an obstacle group or a specific directed obstacle. This will take priority.
Obstacle effort is time-intensive; platoons must immediately start emplacing obstacles. This may mean emplacing lower priority obstacles first while higher priority obstacles are still being planned.
Obstacles shape the engagement area by achieving specific effects: denying enemy access to terrain (block), forcing the enemy to change direction (turn), significantly delaying their movement (fix), or limiting their ability to move freely or maintain their movement formations (disrupt).
- Block is an obstacle effect that integrates fire planning and obstacle effort to stop an attacker along a specific avenue of approach or prevent the attacking force from passing through an engagement area (FM 3-90).
- Turn is an obstacle effect that integrates fire planning and obstacle effort to divert an enemy formation from one avenue of approach to an adjacent avenue of approach or into an engagement area (FM 3-90).
- Fix is an obstacle effect that focuses fire planning and obstacle effort to slow an attacker’s movement within a specified area, normally an engagement area (FM 3-90).
- Disrupt is an obstacle effect that focuses fire planning and obstacle effort to cause the enemy to break up its formation and tempo, interrupt its timetable, commit breaching assets prematurely, and attack in a piecemeal effort (FM 3-90).
Protective obstacles are positioned close to friendly unit positions to disrupt an enemy assault.
Tactical wire obstacles support the defensive scheme, for instance by running along a machine gun FPL.
Determine the obstacle or obstacle groups’ intent with the engineer platoon leader confirming the target, relative location, and effect. Ensure intent supports the commander’s scheme of maneuver.
In conjunction with the engineer platoon leader, identify, site, and mark the obstacles within the obstacle group, tie reinforcing obstacles into natural obstacles.
Ensure coverage of all obstacles with observation and direct and/or indirect fires. Ensure squads can observe and fire on obstacles but also on the terrain the enemy will use when making contact with those obstacles.
Assign responsibility for guides and lane closure as required.
According to METT-TC (I), assist engineer platoons in emplacing obstacles, securing Class IV/V point, and securing obstacle work sites.
Coordinate engineer disengagement criteria, actions on contact, and security requirements with the engineer platoon leader at the obstacle work site.
Assess what effect the obstacle will have on the enemy.
Understand resources required to construct each obstacle effect based off the enemy they are facing.
Understand how the terrain supports the obstacle effect, examples include block, disrupt, fix, and turn.

Figure 5-23. Plans for and integration of obstacles

Plan And Integrate Fires

5-218. The platoon leader, as directed by the company commander and with the assistance of the fire support officer, determines the purpose of fires and where that purpose is best achieved. This plan provides the most effective fires (specifically direct and indirect fires) resources and mitigate the risk of fratricide as the attacking enemy nears the designated engagement areas while supporting air assets conduct army aviation and close air support (CAS) attacks. The following apply in planning and integrating fires (see figure 5-24 on page 5-82):

Determine the purpose of fires
Determine where purpose will best be achieved.
Establish the observation plan that includes—
- Redundancy for each target.
- Observers who will include the FIST, as well as members of maneuver elements with direct fire support execution responsibilities.
Establish triggers based on enemy movement rates.
Obtain accurate target locations using organic target location devices or survey/navigational equipment.
Refine target locations to ensure coverage of obstacles.
Plan final protection fire.
Request critical friendly zone for protection of maneuver elements and no-fire areas for protection of observation posts and forward positions.
When able, leaders walk the terrain with their FOs to ensure the observers can fire targets at pre-planned triggers. This also ensures the observers can provide bottom-up refinement through the fires planning process.

Note. Leaders at the platoon level provide bottom-up refinement on the effectiveness of the higher fire support plan. Leaders at the platoon level have a better appreciation of the terrain within the engagement area because of their proximity to the engagement area.

Figure 5-24. Plans for and integration of fires

Rehearsals

5-219. The purpose of rehearsals is to ensure every leader and Soldier understands the plan and elements are prepared to cover their assigned areas with direct and indirect fires. The rehearsal should cover—

Rearward passage of security forces (as required).
Closure of lanes (as required).
Movement from the hide position (when used) to the battle position.
Use of fire commands, triggers, and maximum engagement lines to initiate direct and indirect fires.
Shifting of fires to refocus and redistribute fire effects.
Disengagement criteria.
Identification of displacement routes and times.
Preparation and transmission of critical reports using radio and digital systems, as applicable.
Assessment of the effects of enemy weapon systems.
Displacement to alternate, supplementary, or subsequent battle positions.
Cross leveling or resupply of Class V.
CASEVAC and MEDEVAC procedures.
Evacuation of casualties.
Friendly passage of lines or reducing own obstacles to counterattack or pursue enemy.

5-220. The platoon leader should coordinate rehearsals with higher headquarters to ensure there are no conflicts with other units. Coordination leads to efficient use of planning and preparation time for all units involved with the operation. It eliminates dangers of misidentifying friendly forces in the rehearsal area, which could result in fratricide.

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