ATP-4-90 Brigade Support Battalion Download
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Brigade Support Area 18 June 2020 4-7 Protect the Base The BSA requires continuous protection from occupation until displacement. Properly designed perimeter security is the base’s first line of defense. Perimeter security is designed to incorporate layered defense in depth and integrate security elements including: cleared fields of fire, interlocking fires, a final protective line, barriers, surveillance, and access control. Units organize a perimeter defense to accomplish a specific mission (such as protecting a base or providing immediate self-protection). Except for very small, dense BSAs no true perimeter defense is possible. The BSB depends upon early warning, key defensive positions, and a quick reaction force. During a perimeter defense, leaders at all levels ensure that— Units physically tie into each other. Direct fire weapons use flanking fire to protect the perimeter. Units utilize indirect fire assets. Communications are secure, and redundant systems are in place. Units employ obstacles. Units establish a final protective line. When the BSB controls the base, the BSB S-3 assigns a perimeter area to each unit collocated on the base. The S-3 ensures each unit’s area of fire mutually supports the adjacent unit’s area, when feasible. The S-3 coordinates with unit commanders and confirms that units in the base have coordinated their boundaries of fire with adjacent units. See Figure 4-2 on page 4-5 for an example of base perimeter area assignments. If a base cluster is used, each unit that controls a base performs the same actions as described for elements on the base. All elements of units in, or transiting through the base, help establishing and defending the base perimeter. Perimeters vary in shape depending on the terrain and situation. If the commander determines the most probable direction of enemy attack, the commander may choose to reinforce that part of the perimeter covering that approach with additional resources. All companies and tenants on the base provide sector sketches to the BSB S-3. Figure 4-3 on page 4-8 depicts an example of a completed company sector sketch. BSB companies and all units in the base draw sector sketches as close to scale as possible. The BSB S-3 combines each sector sketch from the BSB’s subordinate units to create a realistic, complete, and to-scale base sector sketch. Each sector sketch shows at a minimum— Main terrain features in the area of operation and the range to each. Each primary position. Primary and secondary sectors of fire covering each position. Machine gun final protective line or principle direction of fire. Type of weapon in each position. Reference points. Observation post locations. Dead space. Obstacles. Indirect fire targets. Engagement areas if applicable. ATP 4-90