CHAPTER 4

DEFENSIVE OPERATIONS

Battalions defend for many reasons: to retain ground, to gain time, to deny the enemy access to an area, or to defeat the enemy attack. However, defense entails more than just killing the enemy and destroying his equipment before he can move these resources to the battlefield. The enemy's plan, the cohesion and synchronization of his forces, his morale, and his ability to see the battlefield must also be destroyed. Defensive operations must be planned and conducted with the spirit of the offense. Whatever its larger purpose, the immediate challenge of any defensive operation is to recapture the initiative and thus to create the opportunity to shift to the offensive. This chapter describes how the infantry battalion defends within the framework of AirLand Battle.

Section I

DOCTRINE

AirLand Battle doctrine stresses initiative. Even in the defense, offensive action is used to gain the initiative. This requires successful reconnaissance and counterreconnaissance. It also requires that a reserve be maintained for quick transition to the offense. Supporting fires and reinforcing obstacles are planned to shape the battlefield, to disrupt and confuse the enemy, and to destroy the synchronization of his attack.

4-1. PURPOSE

The main purpose of the defense is to defeat the enemy's attack and to regain the initiative. Defense is a temporary measure used to identify or create enemy weaknesses. Use of the defense provides the opportunity to change to the offense.

a. The infantry defends aggressively to accomplish this. It must defend from positions that are mutually supporting and arrayed in depth. It must attack the enemy throughout the depth of his formations.

b. A cohesive defensive plan includes ambushes, reverse slope positions, and depth to disrupt the enemy. Use of these measures forces the enemy to fight in more than one direction; this increases the opportunities to disrupt his command and control, CS, and CSS systems. Thus, friendly forces can regain the initiative and shift to offensive operations.

4-2. CHARACTERISTICS OF DEFENSIVE OPERATIONS

The fundamentals of a successful defense are preparation, disruption, concentration, and flexibility.

a. Preparation. The defender arrives in the battle area before the attacker. He must use his early arrival to prepare thoroughly for combat within his time constraints.

(1) The attacker must learn the terrain by seeing each part of it for the first time. The defender can prepare positions, construct obstacles, and conceal his efforts in advance. The attacker must commit assets to learn where the defender is located. The defender initiates the fight from hard-to-detect stationary positions that provide cover from enemy fire. The attacker must react to the defender by either firing while moving or by seeking covered positions, thereby losing momentum.

(2) The defender develops flexible plans to control fire, movement, communications, and logistics in all possible situations. The attacker must either adhere to a planned scheme and risk destruction, or alter his plan and risk an uncoordinated effort.

(3) The defender must know how enemy units are organized and how they deploy in an attack. He must also know the abilities and limitations of enemy weapons systems and equipment. The battalion S2 provides this information, but the commander must understand it. Thorough preparation begins with sound IPB.

(4) The defender organizes his defense around the weapons most effective against the principal threat. When facing an armored force, the defender's allocation and positioning of antiarmor weapons (TOW missile systems, Dragons, antitank mines, and tanks) is most important; other assets supplement their fires and minimize vulnerabilities. Against an infantry threat, infantry-defeating weapons (machine guns, mortars, artillery, small arms) and antipersonnel obstacles (wire and mines) are integrated to reduce the momentum of the enemy's attack and to destroy the enemy forward of the defender's positions. The effects of all weapons greatly increase when the weapons are positioned where cover and concealment reduce or neutralize enemy suppressive fires.

b. Disruption. The defender must disrupt the synchronization of the enemy's operations. This counters the attacker's initiative and prevents him from concentrating overwhelming combat power against a single part of the defense.

(1) Units maintain OPSEC and avoid patterns to hide their dispositions. Enemy reconnaissance efforts and probing attacks must be defeated without disclosing the scheme of defense to the enemy.

(2) An attacker's strength comes from speed, mass, and the mutual support of maneuver and CS elements. The defender must disrupt the attacker's synchronization and destroy the mutual support between the attacker's combat and CS elements. This makes it hard for the attacker to coordinate and concentrate forces and fires or to isolate and overwhelm the defender.

c. Concentration. The defender is often forced to economize and accept risks elsewhere to gain local superiority in one area. Reconnaissance and security forces must enable him to "see" the battlefield, thereby reducing risk. Due to the limited mobility of infantry weapons, the battalion must concentrate the effects of its weapons rather than the weapons themselves. They should do this before the battle.

(1) The commander concentrates weapons effects by designating the main effort. All elements and assets support and sustain this main effort. By redesignating it, the commander can shift the focus of his combat power. To weight his main effort, the commander can--

(a) Focus counterattack plans to support the main effort.

(b) Reduce the size of the main effort's area of operations.

(c) Assign the main effort priority for obstacles preparation.

(d) Give the main effort priority of indirect fires.

(e) Position the reserve near, in, or behind the main effort.

(2) The commander integrates available assets so that their combined effect on the enemy exceeds the sum of their individual effects.

d. Flexibility. The defender is assured flexibility by sound preparation, disposition in depth, retention of reserves, and effective command and control. Contingency planning permits flexibility. Flexibility also requires that the commander "see the battlefield" to detect the enemy's scheme of maneuver early. IPB determines likely enemy actions, and security elements verify which actions are occurring.

4-3. DEFENSIVE FRAMEWORK

The battalion normally defends as part of a larger force. Because of this, battalion commanders must understand the defensive framework within which divisions and brigades organize and fight.

a. Elements of the Divisional Defense. Divisions fight conventional defenses that are organized into five elements. These elements are complementary, as shown in Figure 4-1. Three of these, security operations, MBA operations, and reserve operations, apply at all echelons. The five elements are as follows:

(1) Deep operations in the area forward of the FLOT.

(2) Security operations forward and to the flanks of the defending force.

(3) Main battle area defensive operations.

(4) Reserve operations in support of the main defensive effort.

(5) Rear operations to retain freedom of action in the rear area.

b. Deep Operations. Deep operations are actions against enemy forces not yet in contact with friendly forces. Deep operations prevent the enemy from massing, and they create opportunities for offensive action by the defender. A deep operation enables the defender to separate the attacking echelons; disrupt the attacker's command and control, CS, and CSS; and slow the arrival times of succeeding echelons. Battalions may participate in deep operations IAW brigade or division plans.

c. Close Operations. Close operations include security area operations, battle handover, and main battle area operations.

(1) Brigade and higher security area operations. The forward security force established by corps or division is called a covering force. This covering force is tactically self-contained--it is organized with enough CS and CSS forces to operate independently from the main body. This force begins the fight against the attacker's leading echelons in the security area. The covering force gains and maintains contact, develops the situation, delays or defeats the enemy's lead forces, and deceives the enemy as to the location of the MBA.

(2) Battalion security area operations. The infantry battalion uses a screening force as its forward security echelon. The exact size and composition of the security force depends on the width of the sector, the nature of the terrain, and the specific tasks the security force is expected to accomplish. It is always tasked with providing early warning. The battalion security force is normally required to establish contact with the covering force, if one is employed, and to aid in its rearward passage and BHO. When no covering force is employed, the battalion security force might be required to move farther forward of the MBA to increase its early-warning ability.

(3) Battle handover. Battle handover provides an orderly transition between the security force battle and combat in the MBA (Figure 4-2). The enemy should be unable to determine that this transition has occurred. The problems inherent in a battle handover arise from when, where, and how the covering force gives up responsibility for the fight to the MBA battalion. The BHL and contact points on the ground must be coordinated and clearly identifiable to both forces. The headquarters that establishes the covering force designates the BHL and sets up contact points to aid contact between MBA units and the covering force. MBA and covering force commanders coordinate and recommend BHL location changes to the higher commander. The BHL is shown on the operation overlay as a phase line. The BHL represents the location where control of the battle passes from the covering force to the MBA commander. The BHL is 2 to 4 kilometers forward of the FEBA, where MBA forces can use direct fire and observed indirect fire to aid the covering force in its final delay, disengagement, withdrawal, and passage of lines. The battle handover takes place at the time or event coordinated between the commanders or as directed by the senior commander.

(4) Main battle area operations. The brigade commander assigns MBA battalion-sized sectors, areas of operation, or battle positions based on his intent and estimate of the situation. The brigade commander can strengthen the effort on the most dangerous avenue by narrowing the sector of the unit astride it or by positioning more forces to cover it. He might be required to use fewer maneuver forces in minimum-risk sectors. The battalion fights the decisive battle in the MBA. The commander positions forces there to control or repel enemy penetrations. He employs reserves to halt the attack, to destroy penetrating enemy formations, and to regain the initiative.

d. Reserve Operations. The primary purpose of the reserve is to retain flexibility. The secondary purpose includes reinforcing success or regaining the initiative through counterattacks. The commitment of reserve forces at the decisive point and time may be the key to the success of a defense. The commander should decide the size, composition, and mission of the reserve early in the planning stage regardless of the defensive technique employed. The reserve is normally positioned near its most probable area of employment. All movement by the reserve to BPs during counterattack or reinforcement occurs on routes that provide cover from direct fire and concealment from ground or air observation. The reserve can also be tasked--

(1) To block any penetration until the enemy is destroyed or additional forces can be committed.

(2) To prepare one or more positions on less dangerous approaches.

(3) To reinforce a forward unit when casualties or heavy enemy pressure reduces its relative combat power.

(4) To counterattack to regain critical positions or terrain.

e. Rear Area Operations. Many command and control, CS, and CSS units are located in the rear area. Their importance, as well as their survivability, reduced mobility, and relatively small-caliber weapons, makes them prime targets for enemy deep attack. However, a maneuver battalion can be assigned a rear area protection mission and can conduct offensive operations there against enemy conventional or unconventional forces.

Section II

PLANNING AND PREPARATION

Defensive doctrine, rather than being prescriptive, allows the commander freedom to plan and conduct his defense. The commander may defend well forward to strike the enemy as he approaches. The commander may fight the defensive battle in the main battle area; or, he may fight a nonlinear defense, drawing the enemy deep into the area of operations then striking his flanks and rear. This section contains considerations for development of defensive COA, based on the types of defense employed by infantry battalions.

4-4. COMMANDER'S INTENT

The commander's intent in defensive situations plays a major role in his development of viable COAs. He normally expresses his intent in terms of the enemy, the terrain, or his own force.

a. Enemy Destruction or Enemy Disruption. When conducting these tasks, soldiers must consider the locations of friendly units and must know their ability to control or retain terrain in order to destroy or disrupt the enemy. Normally, a large reserve is maintained so that units can maneuver aggressively to attack the enemy. The intent should be clarified by control measures that specify which avenues of approach or engagement areas a unit must engage. OPORDs should state which critical targets or elements the friendly unit must destroy--for example, the enemy's reconnaissance forces, reserve forces, infiltrating forces, or logistics formations.

b. Area Denial or Terrain Retention. In certain defensive situations, the enemy is important only if he threatens the unit's control over the terrain or affects battalion operations.

(1) Area denial. The battalion may have a defensive situation in which it must deny an area to the enemy. The enemy must be prevented from using the area for command and control, CS, or CSS operations. For example, a battalion may be given an area-denial task in a specific sector. It can then choose to fight an infiltrating enemy in one of three ways. It can conduct active patrols or ambushes; it can have scouts call for indirect fires; or it can deploy sharpshooters and snipers to kill enemy leaders and reconnaissance elements (Appendix E). It continues these tactics as long as the enemy remains in the battalion sector.

(2) Terrain retention. The battalion may have a defensive mission to hold terrain. That is, it may be required to hold a specific location or sector free of enemy--for example, to secure a decisive terrain feature, LZ, or lodgment area throughout an air assault or airborne operation.

c. Force Preservation. The terrain and enemy are important in this mission only if they aid or threaten the unit's ability to survive or to prepare for other operations. The unit avoids enemy contact and positions itself in terrain that is easily defensible. Use of assembly areas and hide positions are examples of this type of defense.

4-5. DEVELOPMENT OF DEFENSIVE CONCEPT

The restated mission statement and other critical facts and deductions focus the development of the defensive concept. The commander begins developing the course of action by understanding when and where the enemy reconnaissance will probe and when and where the enemy will direct the attack. Therefore, he must --

a. Determine decisive points and the times to focus combat power. The brigade may focus the battalion on a decisive point in an engagement area, or the battalion may be required to determine this point.

b. Determine the results that must be achieved at the decisive point to accomplish the mission. The commander must know the brigade commander's concept and intent.

c. Determine the purposes to be achieved by the main and supporting efforts. The purpose of the main effort is often derived from the battalion's mission statement. The purposes of the supporting efforts must be linked clearly to that of the main effort.

d. Determine the essential tasks of the subordinate units (main and supporting efforts) that achieve these purposes. The assigned task must clearly focus the subordinate unit on the terrain, the enemy, or a friendly unit. A purpose linked with a decisive, attainable, well-defined task produces a good mission statement.

e. Identify types of forces required to accomplish the mission (companies, special platoons, and CS and CSS units as appropriate).

f. Assign command and control headquarters for each of the task-organized units. The commander should fully utilize all subordinate unit commanders and leaders. If additional leaders are required, he uses key coordinating or special staff members.

g. Complete a generic task organization by assigning all organic or attached units.

h. Establish control measures that clarify and support the assigned mission. Control measures should only aid in synchronization. Overuse of control measures can stifle subordinate leader initiative and should be avoided.

i. Ensure the main effort is weighted once the essential part of concept development is completed. He can weight it--

(1) By attaching additional platoons or weapons systems.

(2) By assigning priority of fire or allocating a priority target.

(3) By limiting the area of responsibility of the main effort, which allows the main effort to focus on the critical action.

j. Complete the concept development--

(1) By including the occupation plan for the defense.

(2) By positioning other assets, such as the CP, the battalion mortars, or the trains, and assigning them missions.

(3) By developing the CSS plans for resupply, casualty evacuation, and movement of supplies.

(4) By planning for likely contingencies.

k. Develop this concept within a time framework. He must backwards plan from the following:

• The arrival of the enemy main body.
• The arrival of the enemy reconnaissance forces.
• The preparation time for defensive positions and obstacles.
• The time required for rehearsals.
• The time needed for any required movement.

4-6. LIMITED VISIBILITY OPERATIONS

Battalions must always have plans for both good and limited visibility operations. This is required, since the enemy might not attack during good visibility, and since he can use indirect fires and smoke for obscuration. Also, day attacks can continue into darkness. The battalion must be able to move quickly from its original defensive positions to its limited visibility positions.

a. Technology has changed how soldiers fight on the limited-visibility battlefield. Friendly force use of NVDs and thermal-imaging sights reduces the enemy's advantage in an attack during limited visibility. Despite this fact, limited visibility still reduces effective defensive engagement ranges. Therefore, the commander can expect an attacker to use limited visibility conditions to reconnoiter defender's weapons, obstacles, and positions and to move support elements into position. In addition, the enemy may use the reduced detection distances to infiltrate, breach obstacles, or move elements through gaps in the defender's coverage.

b. Defensive operations during limited visibility--mainly at night--are common. The defender must be able to adapt plans rapidly and to overcome the impact of limited visibility on the defense. To help solve limited visibility problems, the defender--

(1) Uses long-range detection equipment (radar, sensors, NVDs) on well-defined enemy avenues of approach.

(2) Increases surveillance of obstacles, of potential enemy overmatch and assault positions, and of the routes into them.

(3) Repositions some units and weapons along avenues of approach that the enemy will likely use during limited visibility. TRPs must be visible at night for the unit to properly execute its responsibilities in the engagement area.

(4) Uses more resources (infantry, scouts, OPs, patrols, and armor-killer teams) forward on secondary avenues of approach and between positions to detect and slow enemy movement--particularly enemy infiltration. The defender uses the scout platoon on the most important enemy avenue of approach. Units conduct a stand-to each morning and evening IAW battalion SOP (Appendix A).

(5) Uses point obstacles and early warning devices along likely night approaches to slow the enemy and to alert defenders to the presence of the enemy.

(6) Plans and rehearses the required movement of weapons and units and the massing of fires.

(7) Plans illumination on or behind likely engagement areas to silhouette enemy forces and to leave defenders in shadows and darkness.

(8) Begins movement to night defensive positions just before dark and completes the return to daylight positions before dawn.

(9) Uses some of the techniques described for night defense when smoke, dust, heavy rains, snowstorms, fog, or other conditions limit the use of mechanical vision aids. When any of these conditions exist, the defender moves nearer the enemy avenues of approach he is guarding. Sensors can still be useful in limited visibility, and radar can still reveal enemy activity.

Section III

COUNTERRECONNAISSANCE

Counterreconnaissance is defined as the sum of the actions taken at all echelons throughout the depth of the area of operations to counter enemy reconnaissance efforts. Counterreconnaissance is both active and passive; it includes all combat actions designed to deny the enemy information about friendly units by destroying enemy reconnaissance elements (active measures) and by concealing friendly information through OPSEC (passive measures). An analysis of battles throughout history shows that the initial stages of battle are mainly a fight for information. Both sides try to learn as much as possible about each other without committing their main efforts or disclosing their primary positions. The force that wins this battle normally wins the MBA battle.

4-7. PLANNING

Counterreconnaissance is just one aspect of security. The counterreconnaissance force commander is given specific tasks, such as "destroy" or "deny," rather than the general task "conduct counterreconnaissance." Counterreconnaissance continues throughout a defensive operation. It is more than just a forward security area mission. All maneuver units must also plan to counter enemy reconnaissance elements that try to penetrate security forces. All units, including CPs, CS, and CSS units, must establish local security and use hide positions. OPs with an ambush ability should cover obstacles, gaps between units, and avenues of approach. These efforts are coordinated through the S2/S3 to ensure full coverage and to avoid friendly force engagements. The S2 consolidates all counterreconnaissance efforts into the battalion R&S plan. Figure 4-3 shows various considerations for conducting counterreconnaissance functions.

a. Resources. Commanders must have sufficient resources to support the reconnaissance and security effort. Scouts are just part of the counterreconnaissance effort in the security area. Also, counterreconnaissance requires a two-function organization with distinct responsibilities. The first part, finders, conduct surveillance and acquire enemy reconnaissance elements. The second, killers, close with and destroy the enemy elements.

(1) Finders. The finders include scouts, aviation, MI, and FA information gatherers; and maneuver forces. The killers include assets brought forward from the MBA.

(2) Fighters. An MBA maneuver company/team used as a fighter is pushed forward for this purpose and pulled back before the MBA defense is executed. This is risky and difficult to synchronize, but detailed planning and rehearsals reduce the risk and simplify synchronization.

Another technique used in forming the counterreconnaissance unit is that of building a team composed of HHC and maneuver company assets around the HHC commander or the assistant S3. This team must have radios, FOs, medical personnel, and finding and killing systems. Depending on the time the commander estimates the team will be in position, the team may plan to cache water and additional Classes I, V, and VIII.

b. Security Area. The battle in the security area must be planned in the same detail as the one in the MBA. Unity of command is vital. Commanders should be involved in the counterreconnaissance efforts of the battalion; they should fully appreciate the function of the IPB process and the integration of reconnaissance assets. Denying the enemy intelligent enhances the ability to defeat enemy main body forces.

(1) A detailed IPB discloses likely enemy reconnaissance actions. For example, the most likely avenues of approach for mounted and dismounted enemy reconnaissance elements must be identified.

(2) The leader of the counterreconnaissance team receives a detailed order that specifies expected enemy reconnaissance measures and the actions required to counteract them. The S2 recommends to the S3 the placement of the force for final approval by the commander. The unit leader adjusts these positions on the ground to ensure long-range observation and complete, overlapping sector coverage. He reports all adjustments to the main CP and to the command group. Counterreconnaissance forces consist of some or all of the following:

(a) Scouts. Scouts are finders, not killers. In counterreconnaissance operations, they help locate enemy reconnaissance units for destruction by other elements or systems. Scouts can engage the enemy with indirect fire but must avoid direct-fire battles (except in self-defense). Elements that become involved in direct-fire engagements usually stop observing their designated areas, allowing other enemy reconnaissance elements to enter.

(b) Maneuver units. Maneuver units participate in counterreconnaissance by manning OPs, by patrolling, and by practicing OPSEC. Battalion-directed emplacement of PEWS can supplement other sensors, OPs, and patrols. If available, tanks or mechanized forces can help with the counterreconnaissance effort in the forward security area.

(c) TOW systems and MK 19s. TOW systems provide a good long-range observation ability in all environments and conditions in addition to their firepower and mobility. MK 19s can defeat thin-skinned enemy reconnaissance vehicles. However, using TOW missile systems or MK 19s for security missions reduces their availability to prepare for the defense. The commander uses METT-T to determine the mix and allocation of weapons to the counterreconnaissance force and to the MBA force.

(d) Ground surveillance radar. GSR can help identify enemy reconnaissance units, especially during limited visibility. Since GSR is a line-of-sight acquisition system other assets must be used to cover dead spaces. If GSR is located behind scouts, it might mistake scouts moving on the screen line for enemy. To prevent this from happening, GSR can be placed on line with the scouts. The counterreconnaissance team commander positions the GSR with technical advice from the GSR section NCOIC and in coordination with the battalion S2. The counterreconnaissance force provides security for the GSR.

(e) Aviation. Observation, lift, and attack helicopters can help with counterreconnaissance. The counterreconnaissance team commander should get an LO from the aviation unit, include the air battle captain in the planning process and rehearsals, assign specific missions and responsibilities, and define the reporting channels. The ABC should report to the battalion commander. The plan must include contingencies in case aviation elements are unable to fly.

(f) Field artillery. Responsive fire support is vital for a successful counterreconnaissance mission. Based on the IPB, the FSO should develop a flexible fire support plan tailored to the commander's concept. He should ensure the plan is distributed to the leaders of the screening force. Indirect fire is required to the limit of the battalion's observation, normally from 3 to 5 kilometers forward of the security force. The FA battalion commander may need to position one or more batteries forward in the MBA. Detailed coordination of positions, timing, passage lanes, and signals is required. The commander integrates FISTs into the security force to remain mobile, ensuring responsive fire support.

(g) Air defense artillery. Battalion commanders must consider how to provide air defense for counterreconnaissance forces. Stingers and Vulcans extend the battalion ADA umbrella farther into the security area (Chapter 7).

(3) Deception measures can be effective if they are believable. Deception is based on IPB and should have specific objectives. Effective deception techniques include skillfully emplacing heavy concentrations of smoke and frequently repositioning. The deception operation must not disrupt position preparation or remove too many resources from the main effort.

4-8. EXECUTION

The counterreconnaissance force should be emplaced as soon as the battalion either completes an attack or moves into a sector to establish a defense. A retransmission team or relay station may be needed forward to satisfy communications requirements.

a. The killing team should choose a position astride the enemy reconnaissance force's most likely avenue of approach. Leaders of the killing team must know exactly where the scouts and GSR elements are positioned beside or forward of them. Designating "no-movement areas" for specific times also helps prevent fratricide.

b. Observation posts should be planned in depth, not spread out in a line across the battalion front. They should have overlapping fields of observation so the forward OPs can visually hand over the advancing enemy to the next OP. Based on the commander's PIR, some OPs may be required to remain forward and to continue observing NAIs, TAIs, or DPs after the enemy passes. Companies, CPs, and trains should also plan OPs and patrols forward and around their positions.

c. The battalion FSO considers counterreconnaissance operations as priority missions. He ensures the fire support plan will help the counterreconnaissance force strip the initiative from the enemy attacking force.

d. Procedures for communicating with the battalion and with fire support units should be described in the plan. Reports may be passed directly on the command net.

(1) The S2, FSO, and XO should analyze the information from the counterreconnaissance force and other units of the battalion. Speculation by the counterreconnaissance unit may lead to poor preparation in the MBA.

(2) A schedule should be established for making routine reports (Appendix A). This ensures soldiers who occupy OPs remain vigilant and that combat information and negative reports continue to arrive at the main CP.

e. CSS considerations must also be planned in detail. Battalion support assets should be positioned forward initially to reduce response time.

(1) Resupply periods should be planned carefully to prevent the enemy from learning of screening force locations; the movement of resupply vehicles should be restricted. Frequent vehicular movement at night can hinder counterreconnaissance efforts. Also, because the frequent presence of friendly vehicles can make soldiers complacent, enemy reconnaissance elements can enter more easily.

(2) Commanders should develop a responsive casualty evacuation plan. The locations of casualty collection points should be known by all soldiers in the counterreconnaissance force.

f. The position of the counterreconnaissance force commander is an important planning consideration. He should be located centrally or astride the most dangerous enemy avenue of approach.

g. Rehearsals increase the probability of a successful reconnaissance just as they do with any other complex operation. If practical, units should rehearse two drills in particular: acquiring enemy reconnaissance patrols and guiding killing force elements into positions to engage them.

4-9. DISPLACEMENT OF THE COUNTERRECONNAISSANCE FORCE

Planning and executing the withdrawal of counterreconnaissance forces to the MBA are critical. Too often, units underestimate the speed of an enemy attack and withdraw too late. The withdrawal of the screening force should be planned as a rearward passage of lines under enemy pressure. (Chapter 6 provides more information about this type of movement.) Route recognition signals and timing for withdrawal to the MBA must be coordinated and rehearsed between forward security elements and company teams in the MBA. Withdrawal must be planned for both daylight and darkness. Uncontrolled withdrawal to the MBA results in fratricide from friendly obstacles, direct fire, or artillery.

Section IV

CONDUCT OF OPERATIONS

This section aids leaders in executing the operation to accomplish the combat mission through prescribed tactical and defensive techniques.

4-10. OCCUPATION

The scouts are usually the first to reconnoiter the proposed defensive position during this phase. They check for enemy OPs and NBC contamination, establish security, and confirm information as directed by battalion. Leaders then reconnoiter and prepare their assigned areas. Units occupy these areas as soon as practical after receiving the mission. Some assets are brought forward to secure the area and to help prepare or confirm fields of fire for their positions. Security forces, consisting of surveillance and counterreconnaissance units, are established in the security area to prevent enemy observation of position and obstacle preparation. During occupation and setup, movement is reduced to avoid enemy observation.

4-11. PRIORITY OF WORK

Many tasks are accomplished at the same time, but the battalion commander, based on his defensive plan, may give priority to specific tasks. The following is a possible sequence:

a. Position the security force, which includes a counterreconnaissance force.

b. Establish local security for defensive positions.

c. Identify engagement areas and TRPs.

d. Position key weapons (TOW missile systems, MK 19s, Dragons, machine guns, grenade launchers, and available combat vehicles).

e. Site FPFs or other priority targets.

f. Clear fields of observation and fire; determine ranges to probable target locations.

g. Emplace wire, mines, and other obstacles; cover them with fire.

h. Prepare fighting positions and protective positions.

i. Prepare range cards and sector sketches.

j. Establish a wire communications system.

k. Select and prepare routes for supply and evacuation.

l. Prepare alternate and supplementary positions.

m. Confirm and prepare the reserve's position.

n. Rehearse defensive plans, including counterattacks. Focus on the most critical area first.

o. Execute deception plans. Ensure they are IAW higher headquarters' deception plans.

4-12. SEQUENCE OF THE DEFENSE

Defenses are often conducted in the following sequence, because enemy attacks follow this scenario:

a. Defeat of Enemy Reconnaissance and Enemy Preparatory Fires. The enemy uses reconnaissance elements and probing attacks to try to discover the defensive scheme. He also tries to breach or bypass the defender's obstacles. Battalion security forces must use fire and movement to defeat these efforts. At the same time, the enemy may increase the preparatory fires when he increases his reconnaissance efforts. Consistent with the need to maintain security, battalion elements should remain in defilade, should hide, and should prepare positions to avoid the casualties and shock associated with these enemy fires.

b. Approach of the Enemy Main Attack. Battalion security elements observe and report enemy approach movement. Enemy units may approach in columns to ensure rapid advance and to avoid the defender's fires and obstacles. The battalion commander orients his forces against the enemy's main effort. He may initially withhold fires to allow the enemy to close into an engagement area so that, at the decisive time, he can concentrate fires on the enemy formation. His other option is engaging at maximum range with supporting fires and CAS to cause casualties, to slow and disorganize the enemy, to cause the enemy to button up, and to impair enemy communications. Direct-fire weapons are repositioned or maneuvered to attack the enemy from the flank.

c. Enemy Assault. The enemy becomes more vulnerable to obstacles as he deploys. The battalion uses a combination of obstacles and direct and indirect fires to disperse and disrupt the assaulting formation. Some security elements may stay in forward positions to monitor enemy second-echelon movement and to direct supporting fires on these forces as well as on enemy artillery, air defense, supply, and command and control elements. If the enemy assaults, FPFs and all other available fires are placed on his assaulting formations. The decision to use the FPFs can be delegated to platoon leaders in forward platoons. The FPFs are fired only when needed and are terminated or resumed as needed. Prematurely firing FPFs wastes ammunition. Before the enemy penetrates the battalion's defensive sector and seizes or threatens to seize key terrain, the commander should first try to destroy or repel him by using all available fires. If that fails, the commander must decide whether to use his reserves or his least committed forces to block further penetration.

4-13. COUNTERATTACKS

A counterattack is an attack by part or all of a defending force against an enemy attacking force. It is conducted for specific purposes such as regaining lost ground or cutting off or destroying enemy advance units. The objective of a counterattack is to regain the initiative and to prevent the enemy from attaining his purpose in attacking. In sustained defensive operations, a counterattack is conducted to restore the battle position and is directed at limited objectives. The commander must prepare counterattack plans for likely penetrations. Priority is given to areas that are vital to the success of the defense.

a. A counterattack is delivered from a defensive posture. Like other attacks, it depends on surprise and speed of execution and it requires carefully coordinated support from available weapons. The counterattack plan involves one coordinated strike delivered by an appropriate force. Success of a counterattack depends on detailed planning and timing.

b. Penetrations often occur under tactical conditions that would prevent a counterattack and, as such, are not an automatic signal for a counterattack. Therefore, the commander should employ whatever measures are needed to limit penetrations. In the battle position or sector, positions are prepared to add depth to the defense. These positions, when occupied, can limit likely penetrations. If the commander decides that the situation is unfavorable for a counterattack, he orders his reserve to contain the enemy by occupying these prepared positions. He fixes and holds the enemy by fire and informs the next higher commander of his actions.

c. The defending commander evaluates the situation to determine whether he can afford a counterattack, even though one may be needed to reduce the threat. Some of the factors that he must consider are as follows:

(1) Surprise. The counterattacking force gains surprise by using concealed routes to the LD. The force moves--

(a) Under the cover of smoke or noise from supporting weapons.

(b) By coordinating the efforts of all units in the defending force.

(c) By deceiving the enemy as to the time and direction of the counterattack.

(2) Availability of adequate reserves and supporting fires. The commander may need all the soldiers under his command, including reserves, to contain the enemy in the penetrated area. Also, hostile fire may inflict such high casualties within the reserve that the commander no longer has an adequate counterattacking force. If this happens, the commander should fix the enemy by fire from prepared positions and should inform the next higher commander of the situation.

(3) Armored elements in the penetrated area. Defending infantrymen use restrictive terrain to close with and destroy enemy tanks that dominate the penetrated area. If the terrain prohibits them from destroying the tanks, the soldiers counterattack the enemy's flanks and rear from prepared positions to destroy him and most of his tanks.

4-14. SPOILING ATTACKS

Spoiling attacks (Figure 4-4) are mounted to disrupt an expected enemy attack before it is launched. A unit conducting a spoiling attack tries to strike the enemy while he is most vulnerable, while he prepares for an attack in his assembly areas or attack positions, or while he moves to his line of departure. A unit conducts a spoiling attack much like any other attack: it may be either hasty, when time is short; or deliberate, when the unit receives adequate warning. Sometimes, circumstances prevent the unit from fully exploiting this attack, it may either halt on its objective or withdraw to its original position. However, when the situation permits, the unit should exploit the situation as it would in any other attack.

4-15. INTEGRATION OF COMBAT SUPPORT

The key CS elements in the forward defense are those that can destroy infantry. Other CS elements help by acquiring targets or providing security.

a. The mortar platoon provides close and continuous fire support for the battalion. The commander designates a priority of fire to a subordinate unit and allocates its FPF. This method of employment provides flexibility in shifting and massing fire; it also simplifies platoon control and logistics support.

b. Artillery gives the commander a means of projecting destructive power on an enemy at longer ranges. At shorter ranges, artillery is integrated with infantry weapons and mortar fire for added firepower to critical areas. The commander accomplishes this by assigning priority of fire, priority targets, and FPF.

c. Forward observers play a key role in putting these supporting fires on target. FOs must be placed in protected positions where they can observe and report timely and accurate requests for appropriate fires. This positioning requirement may influence the positioning of infantry and other elements.

d. Tactical air support can deliver quantities of cannon fire, iron or smart bombs, and scatterable mines to breakup and destroy massed enemy elements.

e. The main role of the engineers is to provide advice about and emplacement of tactical obstacles. These obstacles reduce the enemy's ability to maneuver, mass, and reinforce, and they increase his vulnerability to fires. Engineers can advise and aid units in building survivability positions and in emplacing protective obstacles. These obstacles protect defensive forces and prevent the enemy from penetrating their positions. If strongpoints are used, engineers help prepare them.

f. Attack helicopters can rapidly and effectively destroy exposed enemy forces that other elements cannot detect or engage. The helicopters' ability to move rapidly to threatened areas enhances their value to a defender threatened by large enemy forces.

g. The scout platoon, though best used for forward security missions, can screen a dangerous flank, maintain contact with adjacent units, patrol gaps between company positions, or perform in an economy-of-force role. Scouts can also operate traffic control points, guide forces conducting rearward passage through the battalion, or perform other infantry tasks.

h. Remotely employed sensors and GSR can help detect the enemy, especially during limited visibility. These resources are initially attached to the security element to monitor forward of the MBA When the security element is withdrawn, REMS and GSR can be employed to cover unoccupied areas between defensive forces and on the flanks of the battalion.

4-16. CONSOLIDATION AND REORGANIZATION

The battalion must quickly reorganize to continue the defense. Attacks are conducted to destroy enemy remnants, casualties are evacuated, and units are shifted and reorganized to respond to losses. Ammunition and other critical items are cross-leveled and resupplied. Security and obstacles are reestablished and reports are submitted.

a. Consolidation. This means reorganizing and strengthening a position after an enemy attack. Consolidation can vary from rapidly redeploying forces and security elements to defeat the next attack to organizing and improving the position. The commander always plans to consolidate after a defense. Planning considerations are as follows:

(1) Reestablish security. Observation posts and screening forces are repositioned.

(2) Eliminate the enemy. Companies ensure remnants of enemy units are captured, destroyed, or forced to withdraw.

(3) Reposition forces in a hasty defense. Armor and antiarmor platoons reposition as needed to cover likely mounted avenues of approach; infantry reorients along likely dismounted avenues of approach. Overmatching forces, TOW missile systems, companies with support-by-tie missions, mortars, the TOC, CSS, and GSRs displace to aid in consolidation.

(4) Plan fires. TRPs can be redesignated as part of the consolidation. Also, indirect fires are modified and existing targets are refined to support the defense.

(5) Conduct reconnaissance. The commander directs companies to conduct mounted or dismounted local patrols along likely enemy avenues of approach while local security is being reestablished. Infantry squads are assigned this task. These squads patrol within the overwatch range of established forces. Scouts are deployed to screen beyond the local patrols.

(6) Prepare for on-order missions. The most likely on-order mission is to continue the defense. During consolidation, the commander and staff continue troop-leading procedures in preparation for on-order missions. Intelligence gathered during reconnaissance is used to adjust plans for contingency missions.

b. Reorganization. This includes all actions to prepare for the next enemy attack or to go on the offense. Reorganization is continuous throughout the defense.

(1) Replace key soldiers. Leadership positions must be filled. If heavy losses have occurred, companies can be reconstituted from the remnants of companies.

(2) Report unit status. Units inform their next higher commander of their location and status.

(3) Evacuate required soldiers and equipment. Casualties, EPWs, and damaged equipment are evacuated or recovered IAW the plans developed before the defense.

(4) Redistribute required items. Supplies, ammunition, and equipment are redistributed by LOGPACs within the units as needed and as time permits.

(5) Plan for further operations. FRAGOS are issued as required. Command and control facilities are located for control during the consolidation and for the conduct of further operations. Units repair gaps in obstacles and continue to improve fighting positions.

Section V

TYPES OF DEFENSE

Many techniques can be used in the defense to capitalize on the abilities of the infantry forces. No best technique exists for defending successfully. The ideal concept may be a combination of several different techniques. This section discusses several techniques that may be used to accomplish the assigned defensive operation. (FMs 3-4, 31-71, 90-3, 90-5, 90-10, and 90-10-1 provide guidance on establishing the defense in unique environments.)

4-17. DEFENSE OF A SECTOR

The defensive operation the battalion commander receives most often is defense of a sector (Figure 4-5). Use of sectors allows flexibility and prevents the enemy from concentrating overwhelming firepower on the bulk of the defending force. Infantry forces defending against an enemy with superior mobility must use the depth of their positions to defeat the enemy. The depth of the defense must come from the initial positioning of units throughout the sector--not from maneuvering. Depth is enhanced by a properly positioned and viable reserve.

a. Positions. A battalion defending against a mounted enemy uses a series of mutually supporting antiarmor BPs. These should be located on armor-restrictive terrain, protected by infantry, and strengthened by obstacles.

b. Security. This disposition is stronger against armor but more vulnerable to infantry attack or combined arms action, which can be directed against one position at a time. Therefore, position preparation must emphasize all-round security and mutual support. (FM 7-10 provides more detailed information about security.)

c. Deployment in Depth. Forces deployed in depth must confront the enemy with effective antiarmor fires from multiple locations as he tries to maneuver. The sector is organized around dispersed, small units, which attack the enemy throughout the depth of his formations. The focus of this technique is the enemy force. Mines and other obstacles, infantry positions, and patrols are used to close gaps that cannot be covered effectively by fire due to terrain masking or heavily wooded areas.

d. Engagement Options. The commander has two engagement options when defending a sector. He chooses one based mainly on the restrictions of the terrain and his expectation of achieving surprise. His first option is to begin engaging at maximum optimum range, based on the terrain and available weapons systems. His second option is to allow the enemy to close to within direct-fire range of antiarmor weapons and machine guns. The defender then engages the enemy with violent hasty and deliberate counterattacks designed to destroy the enemy from any direction. In restrictive terrain, this option denies a more mobile enemy force any firepower or mobility advantage.

(1) Beginning the engagement at long range. The defender initiates fires at long ranges with FA, tactical aircraft, and attack helicopters to begin to breakup the continuity of the attack. As the enemy closes to within range of organic heavy antiarmor weapons, these weapons further disrupt enemy synchronization and destroy key vehicles. When the enemy enters the engagement range of the battalion's organic weapons, antiarmor weapons engage him from multiple unexpected directions and destroy him.

(2) Allowing the enemy into the depth of the position. This technique is offensively oriented. It allows for planned penetration, ambushes, and counterattacks throughout the enemy formation. Armor approaches cannot be defended by a forward array of forces. Such an array can be rapidly overrun or penetrated while under massive artillery, smoke, and direct-fire suppression. To avoid rupture, the battalion must array forces in depth. Concentrating the battalion on narrower fronts is risky.

e. Planning. The commander considers the following factors when facing a mostly mechanized or armored threat:

(1) The commander determines enemy mounted avenues of approach and the size force that can move on each. The commander or S3 estimates the maximum number of vehicles the enemy can deploy at one time on given avenues of approach and the length of time this target array would be exposed.

(2) The commander determines where vehicles can be killed and where antiarmor weapons can be positioned to kill them in these engagement areas. All potential positions throughout the sector are identified. If all positions are used, the commander disperses antiarmor systems. By doing this, he reduces his vulnerability to total suppression. However, he increases the vulnerability of his forces by having many small units that can be defeated in detail or bypassed by dismounted infantry. Dispersion also increases his command, control, and logistical concerns. The commander could go to the other extreme--he could place all his forces in a few positions; this would lessen command and control problems and enhance the security of his forces. However, this extreme makes his antiarmor weapons more vulnerable to suppression and mounted bypass. The prudent commander balances these choices to allow maximum freedom of decentralized action for subordinates.

(3) Dispersion of antiarmor weapons may be modified so that enough infantrymen can be provided to protect these weapons. The infantry prevents dismounted infiltration, provides security for antiarmor weapons (mainly during reduced visibility), and destroys armor at short ranges.

(4) Massing of antiarmor fires is achieved by assigning target engagement areas, primary and alternate sectors of fire, and TRPs. Battalion antiarmor sections can be attached to or in DS of a company. The battalion commander may also keep antiarmor sections in GS under the control of the antiarmor platoon leader or company commander. This is done when weapons are required to cover two or more engagement areas at the same time. To mass antiarmor fires, company Dragons can be placed under battalion control.

(5) The commander plans obstacles to disrupt, fix, turn, or block the enemy, and to protect positions. Encountering these obstacles increases enemy exposure time and enhances the effect of antiarmor fires.

(6) All available fire support is integrated. Planned CAS sorties can provide rapid and concentrated aerial-delivered firepower in the first, crucial engagements of the battle. Mortars and artillery increase the effect of antiarmor weapons by suppressing enemy overwatch elements, forcing enemy armor to button up. Attack helicopters can rapidly mass antiarmor and antipersonnel weapons. They can also provide security on flanks and in other unoccupied areas.

4-18. DEFENSE FROM A BATTLE POSITION

A battle position is a general location and orientation of forces on the ground from which units defend. Battalion-sized to squad-sized units can use BPs (Figure 4-6).

a. Use of battle positions (BPs) reduces the instructions needed to move a force. BPs are often used as graphic control measures for a FRAGO and are identified by number, letter, name, or a combination of these. BPs can be oriented to enemy or terrain.

b. The three levels of preparation for a BP are occupy, prepare, and reconnoiter. The use of on-order BPs with the associated tasks, "prepare" or "reconnoiter," adds flexibility and depth to the defensive plan.

(1) Occupy. The unit must, in positions first occupied, accomplish all actions that must be completed before the assigned mission (FM 7-10).

(2) Prepare. The unit must, from that position, accomplish all actions that will enable it to execute the mission immediately on occupation. Planning, coordinating, and rehearsing are required for the unit to displace to this position and to accomplish the mission from it. Within time constraints, fighting positions are constructed, TRPs are designated, direct-fire and indirect-fire plans are developed, obstacles are emplaced, fields of fire are cleared, and ammunition is prestocked. Prepare missions are normally critical to the defense. A unit assigned such a mission must maintain security on the position and on the routes to it.

(3) Reconnoiter. The unit must coordinate and plan for defense from this position. Leaders reconnoiter, select, and mark positions, routes, and locations for security elements. Movement and other actions, such as the preparation of obstacles and occupation plans, are coordinated with other elements of the battalion.

c. The commander can maneuver his elements freely within the assigned BP. To comply with the commander's intent, units can maneuver outside the BP to adjust fires or to seize opportunities for offensive action. Battalion security, CS, and CSS assets are often positioned outside the BP with approval from the headquarters assigning the BP.

d. The commander allocates space to subordinate elements within the area of the BP, based on the space available and the relative danger of nuclear and chemical attack.

(1) The battalion commander thinks two levels down or in terms of platoon BPs when he selects a BP for subordinate companies. He must allow enough space on each BP for dispersed primary, supplementary, and alternate positions for key weapons.

(2) The battalion commander can vary the degree of maneuver of companies within the battalion BP by allocating larger company BPs. Battle positions can also reflect positions in depth. They may take a shape other than the standard oblong shape, which suggests a linear defense within the BP. Large positions also allow increased dispersion in a nuclear and chemical environment.

e. The commander can combine sectors and BPs within the battalion sector to suit the tactical situation.

4-19. REVERSE SLOPE DEFENSE

A reverse slope defense is organized to use a topographical crest to mask the defender from the attacker's observation and from supporting direct fire (Figure 4-7).

a. The battalion commander may adopt a reverse slope position for elements of the battalion--

(1) When enemy fire makes the forward slope untenable.

(2) When the lack of cover and concealment on the forward slope makes it untenable.

(3) When the forward slope has been lost or not yet gained.

(4) When the forward slope is exposed to enemy direct-fire weapons fired from beyond the effective range of the defender's weapons. Moving to the reverse slope removes the attacker's standoff advantage.

(5) When the terrain on the reverse slope affords better fields of fire than are available on the forward slope.

(6) When the defender must avoid creating a dangerous salient or reentrant in friendly lines.

(7) To surprise the enemy and to deceive him as to the true location of the battalion defensive positions.

b. Some advantages of a reverse slope defense are as follows:

(1) Enemy ground observation of the battle area is masked, even from surveillance devices and radar.

(2) Enemy direct-fire weapons cannot effectively fire on the position without coming within range of the defender's weapons.

(3) The enemy is forced to try to breach obstacles on the reverse slope within direct-fire range of all the defender's weapons. The attacker cannot locate these obstacles until he runs into them.

(4) The enemy is deceived as to the strength and location of defensive positions.

(5) Enemy indirect fire is less effective since he cannot see the defender.

(6) The defender gains tactical surprise.

(7) The lack of enemy ground observation allows more freedom of movement within the battle area.

(8) Dragons, TOW missile systems, and MK 19s, if positioned properly, can mass fires on the reverse military crest; infantry small-arms weapons can contribute their close fires to the battle.

(9) The unit can dig in more quickly even when the enemy is approaching; this is because the slope of the hill covers and conceals the unit from the direct fire and observation of approaching enemy ground forces. Defenders can thus concentrate more fully on position preparation.

(10) The terrain protects the unit from the blast and thermal effects of enemy or friendly force nuclear weapons.

c. Some disadvantages of a reverse slope are as follows:

(1) Observation of the enemy may be limited, and the defender may be unable to cover obstacles to the front by direct fire.

(2) The range of important direct-fire weapons, such as TOW missile systems and MK 19s, may be limited by the topographical crest. However, such weapons may have to be sited separately from infantry to exploit their range.

(3) The enemy holds the high ground in an attack. Therefore, his attack is downhill, but the counterattack is uphill. This may provide a psychological advantage to the enemy.

(4) The effectiveness of the reverse slope defense is reduced during limited visibility, because the reverse military crest must be controlled.

d. The battalion commander organizes the defensive position IAW procedures that apply to all defensive techniques.

(1) The forward edge of the position should be within small-arms range of the crest; however, it should be far enough from the crest that fields of fire allow the defender time to place well-aimed fire on the enemy before he reaches friendly positions.

(2) A reverse slope position is most effective when flanking fires from units on adjacent terrain can be placed on the forward slope.

(3) A security force should be established to the front to stop or delay the enemy, to disorganize his attack, and to deceive him as to the location of the defensive position. When this security element is withdrawn, observation, indirect fire, and security must be maintained to the front.

(4) Observation posts are established on or forward of the topographical crest. This allows long-range observation over the entire front and indirect fire coverage of forward obstacles. OPs are usually provided by the reserve; they may vary in size from a few soldiers to a reinforced squad. They should include FOs. At night, their number should be increased to improve security.

e. The conduct of a reverse slope defense closely parallels that of a forward slope defense. TOW missile systems, MK 19s, and tanks (if available) may be positioned first on the forward slope to engage the enemy at long ranges. As the enemy nears, they move to positions on the reverse slope or on the forward slope of the next hill to the rear (counterslope).

f. Two other adaptations remain for the reverse slope defense of an area (Figure 4-8).

(1) Firing positions are prepared on or forward of the topographical crest when the commander wants to use the fields of fire afforded by the forward slope. However, the personnel manning these positions remain on the reverse slope to reduce their exposure to fire. Only a skeleton force is kept forward to slow the attackers while the rest of the soldiers occupy their fighting positions. Reserves are held in covered positions. These forces are used for counterattacks either over -the crest or around the flanks of the hill.

(2) The enemy may be denied the hill or suffer high casualties fighting for it even if neither the forward nor reverse slope is suitable for the BP. The defender can engage the enemy on the reverse slope from positions on other hills. Mortar, FA, and long-range machine gun fires are targeted on the reverse slope, the crest, and the forward slope. Using flanking hills for positions often allows grazing machine gun fire, which rakes otherwise protected areas just over the crest.

4-20. PERIMETER DEFENSE

A perimeter defense is oriented in all directions. The battalion can organize a perimeter defense to accomplish a specific mission or to provide immediate self-protection such as during resupply operations. A perimeter is established when the battalion must hold critical terrain in areas where the defense is not tied in with adjacent units. This can occur when the battalion is operating behind enemy lines or when it is securing an isolated objective such as a bridge, mountain pass, or airfield. The battalion may also form a perimeter when it has been bypassed and isolated by the enemy and must defend in place.

a. The need to hold or protect features, such as bridges, airfields, or LZs, from enemy observation and fires may restrict the positioning of units within a perimeter. These factors, and an inability to achieve depth, also make a perimeter defense vulnerable to armor. The commander reduces these vulnerabilities by doing the following:

(1) Positioning antiarmor weapons systems on armor-restrictive terrain to concentrate fires on armor approaches.

(2) Providing as much depth as the diameter of the perimeter allows through his location of security elements, the reserve, and secondary sectors of fire of antitank weapons.

(3) Constructing obstacles to fix or block the enemy so he can be effectively engaged.

b. Perimeters vary in shape, depending on the terrain and situation. If the commander determines the most probable direction of enemy attack, he may weight that part of the perimeter to cover that approach. The perimeter shape conforms to the terrain feature that best uses friendly observation and fields of fire. The effectiveness of the perimeter maybe enhanced by tying it in to a natural obstacle, such as a river, which allows combat power to be concentrated in more threatened sectors (A, Figure 4-9).

c. Several methods maybe used to organize a battalion perimeter. One method is to place all platoons in the battalion in positions on the perimeter (B, Figure 4-9). This is least desirable since it facilitates an enemy penetration. However, certain positioning techniques can create some depth in the defense.

(1) The perimeter is divided into company sectors with boundaries and coordinating points, which are established based on the same considerations discussed earlier. When possible, two platoons (each with three squads abreast) are placed on the outer perimeter and one on the inner perimeter of each sector (C, Figure 4-9). This gives depth to the company position and facilitates control. It gives one platoon from each rifle company the mission to support front-line platoons (just as in the defense). Also, it enables the company commander to locate his CP and his 60-mm mortars near the reserve platoon, enhancing control and security.

(2) The battalion commander may elect to assign two rifle companies to the outer perimeter and the third to an inner perimeter (D, Figure 4-9). Regardless of the method used, the inner perimeter should be far enough from the outer perimeter to prevent the enemy from suppressing both with the same fires. However, the inner perimeter must be close enough to support the outer perimeter with small-arms fire. Gaps on the outer perimeter between units in open terrain must be covered by fire. When units are in restrictive terrain with restricted fields of fire and observation, no gaps should be allowed, and a narrower frontage may be required. This may also require the company commander to deploy all his platoons on line.

d. The commander ensures the outer perimeter positions have rearward protection from inner perimeter weapons once the inner perimeter is established.

e. Combat vehicles supporting the defense are normally assigned firing positions on the perimeter, covering the most likely mounted avenue of approach. Additional firing positions and routes to them should be selected and prepared. If the perimeter has several mounted approaches, combat vehicles may be held in a mobile position. Therefore, units must prepare routes, firing positions, and range cards for all positions in advance. Also, commanders must ensure that vehicles do not destroy wire communications.

f. Isolation may drive the battalion commander to form a perimeter. If so, combat and combat support elements from other units may seek the battalion's protection. These units are given missions based on their support abilities. Any fire support provided from outside the perimeter is coordinated and integrated into the overall defensive plan. This extra fire support conserves the ammunition of units within the perimeter.

g. The battalion commander normally employs the scout platoon outside the perimeter for early warning. He may augment security with squad-sized or smaller elements, which are provided and controlled by units on the perimeter. The security elements are positioned to observe avenues of approach. Patrols cover areas that cannot be observed by stationary elements. If the scout platoon remains under battalion control, it must coordinate with units on the perimeter for a passage of lines (Chapter 6).

h. Reserve elements may consist of a designated unit or a provisional force organized from headquarters and support personnel. They form the second line of defense behind the perimeter elements. Ideally, reserves are mobile enough to react to enemy action in any portion of the perimeter. They are positioned to block the most dangerous avenue of approach and are assigned on-order positions on other critical avenues. If available, combat vehicles initially occupying firing positions on the perimeter may be tasked to reinforce the reserve on-order.

i. The perimeter defense is conducted much like a forward defense. Mortars, FA, tanks, and TOW missile systems engage the enemy at long ranges. As the enemy comes within small-arms range, other weapons on the perimeter engage him. If the assault continues, FPFs are fired. If the perimeter is penetrated, the reserve blocks the penetration or counterattacks to restore the perimeter. After committing the initial reserve, the commander must reconstitute a reserve to meet other threats. This force normally comes from an unengaged unit in another portion of the perimeter. If an unengaged force is used to constitute anew reserve, sufficient forces must be retained to defend the vacated sector.

j. CSS elements may support from within the perimeter or from another location, depending on the mission and status of the battalion, the type of transport available, the weather, and the terrain. Resupply is often by air. The availability of LZs and DZs protected from the enemy's observation and fire is a main consideration in selecting and organizing the position. Since aerial resupply is vulnerable to weather and enemy fires, commanders must emphasize supply economy and protection of available stocks.

4-21. LINEAR DEFENSE

The commander commits most of his combat power to the FEBA when he must locate his main effort well forward. Using this linear defensive technique, he must plan to defeat the enemy early when the enemy is still arrayed along the FEBA or beyond it. This technique is more difficult to execute than a defense in greater depth--it lacks flexibility due to the early commitment to decisive combat. Also, this technique depends on rapid and accurate identification of and concentration against the enemy main effort.

a. Conditions. Adoption of a linear defense may be appropriate--

(1) When defensible terrain, such as along a significant obstacle, is available in the forward part of the battalion's sector.

(2) When the enemy threat is mainly infantry.

(3) When natural or man-made obstacles neutralize the mobility of a mounted enemy, forcing him to attack dismounted.

(4) When specific terrain along the FEBA must be retained.

(5) When enough resources are available to provide the required density of combat power across the sector to detect and stop an infantry attack.

b. Characteristics. A linear defense has interlocking and overlapping observation and fields of fire along the FEBA to preclude penetration. The bulk of the maneuver units is forward to gain interlocking small-arms fire within and between companies. The main effort is assigned to the most likely avenues of enemy approach. The reserve is usually small and is used to reinforce forward units, to give depth to the defense, to block penetrations, or to counterattack to regain key terrain. If available, tanks form the basis of a counterattack force

c. Organization. The battalion commander considers several points when establishing the linear defense as part of COA development. He must gain mutual support between companies when arraying his forces linearly. To do this, he visualizes the building of the defense using infantry platoons as building blocks. In addition, he must--

(1) Identify enemy avenues of approach and determine the size enemy force that can use each avenue. He must also allocate enough infantry platoons to block the avenues by fire and to cover gaps. Finally, he must allocate and position the battalion reserve.

(2) Determine how to divide his area among his companies. Areas of responsibility, or sector locations, are designated by coordinating points and lateral boundaries. The commander tries to keep his company commanders' control problems to a minimum. He locates coordinating points and lateral boundaries so that avenues of approach or major terrain features are not divided. He tries to concentrate forces where enemy attacks are most likely and to give wider sectors to less threatened units.

(3) Consider that lateral boundaries should provide suitable terrain and depth for companies to deploy their mortars and support elements.

4-22. DEFENSE OF A STRONGPOINT

The mission to create and defend a strongpoint implies retaining terrain to stop or redirect strong enemy formations. Strongpoints are usually on high-speed enemy avenues of approach. They are tied to the defensive positions of units on their flanks (Figure 4-10). A bypassed strongpoint exposes the enemy's flanks to attacks from friendly forces in and outside the strongpoint. Battalion strongpoints can be established in isolation only when tied to restrictive terrain on their flanks.

a. The battalion pays a high cost in manpower, time, and assets for building a strongpoint. To build one requires many days of dedicated work, normally with engineer support. As a guideline, a strongpoint requires at least one day of effort from an engineer organization the size of the defending force.

b. A strongpoint cannot be easily bypassed, so repeated dismounted assaults must be expected and repelled. The strongpoint receives intensive artillery attacks and must be prepared with sufficient overhead cover. Also, defense in depth is achieved through multiple positions within the strongpoint. If used, combat vehicles dig in multiple firing positions, while dismounted infantry use positions tied together with trenches. Strongpoints maybe on the FEBA or in depth in the MBA (Figure 4-11).

c. The battalion commander and the commander of the supporting engineer unit must conduct a ground reconnaissance to determine their priorities of position construction. The first priority is to make the position impassable to armor. The second priority is to protect the antiarmor weapons with terrain, obstacles, and infantry. The third priority is to protect infantrymen who are guarding antiarmor weapons.

d. The battalion establishes security around a strongpoint before occupying it. A typical security force consists of a scout platoon, remote sensors, and radar. It may also include a maneuver platoon or company. The battalion must consider leaving stay-behind OPs to report enemy activity and to disrupt the enemy with indirect fire.

e. Tanks (if available), TOW missile systems, and MK 19s may first be positioned in BPs, if defensible terrain is available forward of the strongpoint, to begin disrupting and destroying the enemy early. Pushing mobile force-s forward also deceives the enemy as to the location of the main effort. As the enemy nears the forward positions, available TOW missile systems and tanks move to their primary positions, drawing the enemy into prepared engagement areas. These elements must anticipate the speed of the advancing enemy and establish criteria so they can begin disengaging before they are decisively engaged. This distance is 2 or 3 kilometers against a mounted enemy. Scouts occupy OPs to observe the enemy and to adjust fire, assisting maneuver elements that are returning to the strongpoint.

f. The battalion selects and prepares positions and routes such that combat vehicles can be moved to supplementary and alternate positions within the strongpoint. All positions within a strongpoint are mutually supporting, with interconnecting trenches to allow rapid reinforcement of a threatened area. Proper positioning also allows the massing of fire from two or more units against an assault. This prevents the enemy from isolating positions and defeating them in detail.

g. ADA weapons may first be positioned forward with the security element. Also, mortars normally operate in split section and are GS to the battalion.

h. Combat trains are in defilade positions or buildings within the strongpoint. Supplies are pre-positioned near primary, alternate, and supplementary positions. The MSR to the field trains is kept open as long as possible.

4-23. DEFENSE AGAINST INFILTRATION

Infiltration is a constant threat to a defense usually when forces in the forward defense area are dispersed. The enemy may try an infiltration to disrupt operations and to harass installations in the rear area, or he may try a massive infiltration. Specific measures to aid in controlling infiltration include extensive counterreconnaissance, combat patrols, antipersonnel obstacles, warning devices, NVDs, and electronic surveillance devices. If the threat of attack by infiltration exists, a mobile combat force receives the mission of engaging the infiltration forms once they are detected.

4-24. DEFENSE AGAINST AIR ATTACK

Air defense measures performed by the battalion include passive protective measures such as using a warning system, assigning firing areas, and attacking air targets IAW established ROE. Air defense units may operate in the battalion area under the control of battalion or higher headquarters (FM 44-100).