Infantry Drills

FM 3-21.8 – Chapter 8 – Section II – Sequence of the Defense

Section II – Sequence of the Defense

8-11.     As part of a larger element, the platoon conducts defensive operations in a sequence of integrated and overlapping phases. This section focuses on the following phases within the sequence of the defense:

– Reconnaissance, security operations, and enemy preparatory fires.

– Occupation.

– Approach of the enemy main attack.

– Enemy assault.

– Counterattack.

– Consolidation and reorganization.


8-12.     Security forces must protect friendly forces in the main battle area (MBA) and allow them to prepare for the defense. The goals of a security force include providing early warning, destroying enemy reconnaissance elements (within its capability), and disrupting enemy forward detachments or advance guard elements. The platoon may be attached to a larger element or remain with the parent company to conduct counter-reconnaissance. Additionally, the platoon may conduct security operations as part of the company defensive plan by conducting patrols or manning observation post(s) (OP) to observe named area(s) of interest (NAI).

8-13.     The platoon may also be required to provide guides to the passing friendly security force and may be tasked to close the passage lanes. The passage could be for friendly forces entering or departing the security zone, and may include logistics units supporting the security forces. The platoon, as part of a larger force, may also play a role in shaping the battlefield. The battalion or brigade combat team commander may position the company to deny likely enemy attack corridors. This will enhance flexibility and force enemy elements into friendly engagement areas.

8-14.     When not conducting security or preparation tasks, the Infantry platoon normally occupies dug-in positions with overhead cover to avoid possible enemy artillery preparatory fires.


8-15.     The occupation phase of the defense includes moving from one location to the defensive location. A quartering party under company control normally leads this movement to clear the defensive position and prepares it for occupation. The platoon plans, reconnoiters, and then occupies the defensive position. The battalion establishes security forces. The remaining forces prepare the defense. To facilitate maximum time for planning, occupying, and preparing the defense, leaders and Soldiers at all levels must understand their duties and responsibilities, including priorities of work (covered in the WARNO or by a unit TSOP).

8-16.     Occupation and preparation of the defense site (see Section V of this chapter) is conducted concurrently with the TLP and the development of the engagement area (if required). The platoon occupies defensive positions IAW the company commander’s plan and the results of the platoon’s reconnaissance. To ensure an effective and efficient occupation, the reconnaissance element marks the friendly positions. These tentative positions are then entered on the operational graphics. Each squad moves in or is led in by a guide to its marker. Once in position, each squad leader checks his position location. As the platoon occupies its positions, the platoon leader manages the positioning of each squad to ensure they locate IAW the tentative plan. If the platoon leader notes discrepancies between actual positioning of the squads and his plan, he makes the corrections. Security is placed out in front of the platoon. The platoon leader must personally walk the fighting positions to ensure that everyone understands the plan and that the following are IAW the plan:

– Weapons orientation and general sectors of fire.

– Crew served weapons positions.

– Rifle squads’ positions in relation to each other.

8-17.     Each squad leader ensures he knows the location of the platoon leader and platoon sergeant for command and control purposes, and where the casualty collection point is located. The platoon may be required to assist engineers in the construction of tactical obstacles in their sector. All leaders must know where these obstacles are so they can tie them into their fire plan.

8-18.     When the occupation is complete, subordinate leaders can begin to develop their sector sketches (paragraph 8-100) based on the basic fire plan developed during the leader’s reconnaissance. Positions are improved when the direct fire plan is finalized and proofed. In addition to establishing the platoon’s primary positions, the platoon leader and subordinate leaders normally plan for preparation and occupation of alternate, supplementary, and subsequent positions. This is done IAW the company order. The platoon and/or company reserve need to know the location of these positions. The following are tactical considerations for these positions.

Alternate Positions

8-19.     The following characteristics and considerations apply to an alternate position:

– Covers the same avenue of approach or sector of fire as the primary position.

– Located slightly to the front, flank, or rear of the primary position.

– Positioned forward of the primary defensive positions during limited visibility operations.

– Normally employed to supplement or support positions with weapons of limited range, such as Infantry squad positions. They are also used as an alternate position to fall back to if the original position is rendered ineffective or as a position for Soldiers to rest or perform maintenance.

Supplementary Positions

8-20.     The following characteristics and considerations apply to a supplementary position:

– Covers an avenue of approach or sector of fire different from those covered by the primary position.

– Occupied based on specific enemy actions.

Subsequent Positions

8-21.     The following characteristics and considerations apply to a subsequent position:

– Covers the same avenue of approach and or sector of fire as the primary position.

– Located in depth through the defensive area.

– Occupied based on specific enemy actions or conducted as part of the higher headquarters’ scheme of maneuver.


8-22.     As approach of the enemy main attack begins, brigade combat team and higher headquarters engage the enemy at long range using indirect fires, electronic warfare, Army attack aviation, and close air support (CAS). The goal is to use these assets and disrupting obstacles to shape the battlefield and or to slow the enemy’s advance and break up his formations, leaving him more susceptible to the effects of crew served weapons. As the enemy’s main body echelon approaches the battalion engagement area, the battalion may initiate indirect fires and CAS to weaken the enemy through attrition. At the same time, the brigade combat team’s effort shifts to second-echelon forces, depending on the commander’s plan. Based on an event stated in the company commander’s order, Infantry platoons cease security patrols and bring OPs back into the defense at a predetermined time. Positions may be shifted in response to enemy actions or other tactical factors.


8-23.     During an enemy assault attacking enemy forces attempt to fix and finish friendly forces. Their mission will be similar to those in friendly offensive operations: destroy forces, seize terrain, and conduct a penetration to pass follow-on forces through. During execution of the defense, friendly forces will mass the effects of fires to destroy the assaulting enemy. The platoon leader must determine if the platoon can destroy the enemy from its assigned positions.

Fighting From Assigned Positions

8-24.     If the platoon can destroy the enemy from its assigned positions, the platoon continues to fight the defense.

8-25.     The platoon leader continues to call for indirect fires as the enemy approaches. The platoon begins to engage the enemy at their weapon systems’ maximum effective range. They attempt to mass fires and initiate them simultaneously to achieve maximum weapons effects. Indirect fires and obstacles integrated with direct fires should disrupt the enemy’s formations, channel him toward EAs, prevent or severely limit his ability to observe the location of friendly positions, and destroy him as he attempts to breach tactical and or protective obstacles. If there is no enlisted tactical air controller (ETAC) available, the forward observer or platoon leader will be prepared to give terminal guidance to attack aviation if available and committed into his area of operations.

8-26.     Leaders control fires using standard commands, pyrotechnics, and other prearranged signals. (See Chapter 2, Employing Fires, for more information.) The Infantry platoon increases the intensity of fires as the enemy closes within range of additional friendly weapons. Squad leaders and team leaders work to achieve a sustained rate of fire from their positions by having buddy teams engage the enemy so both Soldiers are not reloading their weapons at the same time. To control and distribute fires, leaders consider—

– Range to the enemy.

– Engagement criteria (what to fire at, when to fire [triggers], and why).

– Most dangerous or closest enemy targets.

– Shifting to concentrate direct fires either independently or as directed by higher headquarters.

– Ability of the platoon to engage dismounted enemy with enfilading, grazing fires.

– Ability of the platoon’s SLM and CCMS to achieve flank shots against enemy vehicles.

8-27.     When the enemy closes on the platoon’s protective wire, machine guns fire along interlocking principal direction(s) of fire (PDF) or final protective line(s) (FPL) as previously planned and designated. Other weapons fire at their designated PDFs. Grenadiers engage the enemy with grenade launchers in dead space or as the enemy attempts to breach protective wire. The platoon leader requests final protective fire (FPF) if it is assigned in support of his positions.

8-28.     The platoon continues to defend until it repels the enemy or is ordered to disengage.

Fighting From Other Than Assigned Positions

8-29.     If the platoon cannot destroy the enemy from its assigned positions, the platoon leader reports the situation to the company commander and continues to engage the enemy. He repositions the platoon (or squads of the platoon) when directed by the commander in order to—

– Continue fires into the platoon engagement area.

– Occupy supplementary or alternate positions.

– Reinforce other parts of the company.

– Counterattack locally to retake lost fighting positions.

– Withdraw from an indefensible position using fire and movement to break contact.


NOTE:  The platoon leader does not move his platoon out of position if it will destroy the integrity of the company defense. All movements and actions to reposition squads and the platoon must be thoroughly rehearsed.


8-30.     As the enemy’s momentum is slowed or stopped, friendly forces may counterattack. The counterattack may be launched to seize the initiative from the enemy or to completely halt his attack. In some cases, the purpose of the counterattack will be mainly defensive (for example, to reestablish the forward edge of the battle area [FEBA] or to restore control of the area). The Infantry platoon may participate in the counterattack as a base-of-fire element or as the counterattack force. This counterattack could be planned or conducted during the battle when opportunities to seize the initiative present themselves.


8-31.     The platoon secures its sector and reestablishes the defense by repositioning friendly forces, destroying enemy elements, treating and evacuating casualties, processing EPWs, and reestablishing obstacles. The platoon conducts all necessary sustainment functions, such as cross-leveling ammunition and weapons, as it prepares to continue defending. Squad and team leaders provide liquid, ammunition, casualty, and equipment (LACE) reports to the platoon leader. The platoon leader reestablishes the platoon chain of command. He consolidates squad LACE reports and provides the platoon report to the company commander. The platoon sergeant coordinates for resupply and supervises the execution of the casualty and EPW evacuation plan. The platoon continues to repair or improve positions, quickly reestablishes observation posts, and resumes security patrolling as directed.

8-32.     Consolidation includes organizing and strengthening a position so it can continue to be used against the enemy. Platoon consolidation requirements include:

– Adjusting other positions to maintain mutual support.

– Reoccupying and repairing positions and preparing for renewed enemy attack.

– Relocating selected weapons to alternate positions if leaders believe the enemy may have pinpointed them during the initial attack.

– Repairing any damaged obstacles and replacing any Claymore mines.

– Reestablishing security and communications.

8-33.     Reorganization includes shifting internal resources within a degraded friendly unit to increase its level of combat effectiveness. Platoon consolidation requirements include:

– Manning key weapons as necessary.

– Providing first aid and preparing wounded Soldiers for CASEVAC.

– Redistributing ammunition and supplies.

– Processing and evacuating EPWs.

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