Infantry Drills

FM 3-21.8 – Chapter 8 – Section I – Characteristics of the Defense

Section I – Characteristics of the Defense

8-1.        Following are the characteristics of the defense that constitute the planning fundamentals for the Infantry platoon:

– Preparation

– Security

– Disruption

– Massing effects

– Flexibility

8-2.         To ensure the success of the defense, the platoon leader must understand the characteristics of the defense and apply TLP during planning, preparation, and execution of the operation.


8-3.        The friendly defender arrives in the battle area before the enemy attacker. As the defender, the platoon must take advantage of this by making the most of preparations for combat in the time available. By thoroughly analyzing the factors of METT-TC, the platoon leader gains an understanding of the tactical situation and identifies potential friendly and enemy weaknesses.

8-4.        By arriving in the battle area first, the Infantry platoon has the advantage of preparing the terrain before the engagement. Through the proper selection of terrain and reinforcing obstacles, friendly forces can direct the energy of the enemy’s attack into terrain of their choosing. Friendly forces must take advantage of this by making the most thorough preparations that time allows while always continuing to improve their defenses—security measures, engagement areas, and survivability positions. Preparation of the ground consists of plans for fires and movement; counterattack plans; and preparation of positions, routes, obstacles, logistics, and command and control (C2) facilities.

8-5.        The Infantry platoon must exploit every aspect of terrain and weather to its advantage. In the defense, as in the attack, terrain is valuable only if the friendly force gains advantage from its possession or control. In developing a defensive plan, the friendly force takes account of key terrain and attempts to visualize and cover with fire all possible enemy avenues of approach into their sector. The friendly defense seeks to defend on terrain that maximizes effective fire, cover, concealment, movement, and surprise.

8-6.        Friendly forces must assume that their defensive preparations are being observed. To hinder the enemy’s intelligence effort, leaders establish security forces to conduct counter reconnaissance and deceive the enemy as to the exact location of the main defenses.


8-7.        The goals of the platoon’s security efforts are normally tied to the company efforts. These efforts include providing early warning, destroying enemy reconnaissance units, and impeding and harassing elements of the enemy main body. The platoon will typically continue its security mission until directed to displace.


8-8.        Defensive plans vary with the circumstances, but all defensive concepts of the operation aim at disrupting the enemy attacker’s synchronization. Counterattacks, indirect fires, obstacles, and the retention of key terrain prevent the enemy from concentrating his strength against selected portions of the platoon’s defense. Destroying enemy command and control vehicles disrupts the enemy synchronization and flexibility.  Separating enemy units from one another allows them to be defeated piecemeal.


8-9.        The platoon must mass the overwhelming effects of combat power at the decisive place and time if it is to succeed. It must obtain a local advantage at points of decision. Offensive action may be a means of gaining this advantage. The platoon leader must remember that this massing refers to combat power and its effects—not just numbers of Soldiers and weapons systems.


8-10.     Flexibility is derived from sound preparation and effective command and control and results from a detailed analysis of the factors of METT-TC, an understanding of the unit’s purpose, and aggressive reconnaissance and surveillance. The platoon must be agile enough to counter or avoid the enemy attacker’s blows and then strike back effectively. For example, supplementary positions on a secondary avenue of approach may provide additional flexibility to the platoon. Immediate transitions from defense to offense are difficult. To ease this transition, the platoon leader must think through and plan for actions his platoon may need to take, and then rehearse them in a prioritized sequence based on time available.


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