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Military

CHAPTER 9

Defense

OPERATIONS IN DEPTH

The goal of a defensive operation is to defeat the enemy's attack and transition to the offense. To reach this goal, engineers provide synchronized engineer efforts to deep, close, and rear operations.

The engineer effort in support of deep operations includes analyzing terrain and identifying probable enemy AAs. It also includes planning and executing situational obstacles to disrupt enemy forces. These forces may include committed, reserve, or follow-on enemy units.

During close operations, engineers shape EAs by integrating the effects of direct and indirect fires and tactical obstacles. Engineers plan, coordinate, and synchronize survivability operations to support protecting friendly forces. Finally, they allocate mobility assets to the counterattack force.

Engineers ensure the survivability of C2 and CSS assets by constructing protective positions and providing assistance in constructing protective obstacles. They strengthen base-cluster defenses with obstacles. Engineers also maintain MSRs and facilities.

PERSPECTIVE:

When Germany launched its offensive from the Eifel region against the First United States Army lines in the Ardennes section of Belgium and Luxemburg, it marked the beginning of the Battle of the Bulge. It also set the stage for the development of the largest continuous minefield ever laid on any American division front. The 1st Engineer Combat Battalion planned and installed this extensive 12-mile minefield of 31,480 antitank mines, 127 antipersonnel mines, and 38 trip flares in two weeks, beginning on 20 December. The minefield aided the 1st Infantry Division in firmly repelling three of Von Rundstedt's best divisions, thereby preventing a successful breakthrough in the Monschau shoulder.

ENGINEER FOCUS IN THE DEFENSE

Five engineer functions provide the maneuver commander combat multipliers that significantly increase his combat effectiveness. Understanding the fundamentals of the engineer functions is imperative to successful integration into the maneuver unit's plans.

MOBILITY

Engineers focus on maintaining the force's freedom of maneuver. Counterattack routes are left clear of obstacles or have prepared breaches through friendly obstacles. Engineers construct combat roads and trails for counterattacks and lateral movement between fighting positions. During the fight, engineers rapidly reduce obstacles created by enemy fires, sabotage, or SCATMINEs to maintain friendly freedom of maneuver. Engineers conduct breaching and assault-bridging operations to the reserves or counterattack force.

COUNTERMOBILITY

Engineers integrate tactical-obstacle development to attack the enemy and complement the friendly scheme of maneuver. Tactical obstacles directly attack the enemy's ability to move, mass, and reinforce. Engineers ensure obstacle integration through the proper exercise of obstacle C2, focusing on obstacle-emplacement authority and obstacle control. Engineers facilitate granting obstacle-emplacement authority and obstacle control by developing specific obstacle-control measures. The specific control measures used vary with the echelon of obstacle planning. Finally, engineers ensure that obstacles are reported and that information is disseminated. FM 90-7 is the primary reference for countermobility planning.

Obstacle-Emplacement Authority

Obstacle-emplacement authority is the authority that a unit commander has to emplace reinforcing obstacles. In a TO, theater commanders have the authority to emplace obstacles. Usually, they delegate the authority to corps commanders who delegate it to division commanders. Division commanders retain authority unless a higher commander withholds or restricts it.

Obstacle Control

Obstacle control is the control that commanders exercise to ensure that obstacles support current and future operations. Obstacle control ensures that subordinate commanders emplace obstacles to best support the higher commander's scheme of maneuver. Obstacle control also ensures that subordinate commanders do not emplace obstacles that will interfere with future operations.

Obstacle-Control Measures

Obstacle-control measures are specific control measures that simplify granting obstacle-emplacement authority and providing obstacle control. Obstacle-control measures are obstacle zones, belts, groups, and restrictions.

Echelons of Planning

The nature of obstacle integration from theater level to company/team leads to an echelonment of obstacle planning. At each lower level, engineers conduct more detailed planning. At theater level, planning consists of developing obstacle restrictions and granting obstacle-emplacement authority to subordinate elements. At the company/team level, planning consists of the detailed design and siting plans to emplace and integrate the directed obstacles in the TF obstacle groups. The echelonment of obstacle planning requires engineers at each level to provide subordinate units with the right combination of positive control and flexibility. At each level, obstacle planning builds on the obstacle plan from higher echelons. Table 9-1 shows examples of appropriate obstacle planning at each level.

Obstacle Reporting

Obstacle reporting is a maneuver commander's responsibility at every level. Staff engineers assist him with this responsibility. Engineer units also report obstacle status through engineer channels from the emplacing-unit level to the authorizing-command level.

SURVIVABILITY

Survivability operations include all the aspects of protecting personnel, weapons, and supplies. Engineers plan and construct fortifications such as fighting positions for combat vehicles or protective positions for C2 nodes or supplies. Engineers provide equipment and technical assistance to help units construct other fortifications and protective obstacles. Camouflage and deception operations are other key engineer contributions to survivability. Engineers conceal their critical activities and provide equipment and technical assistance to assist in camouflaging key C2 nodes and CSS activities. An observed engineer effort is effective in painting a false picture. Dummy obstacles, phony minefields, and shallow ditches and weapons positions can be used to deceive and aid force survivability.

GENERAL ENGINEERING

Sustaining defensive operations requires extensive engineer support. Corps engineer units, augmented with engineers from the TA, provide most of the general-engineering effort. Critical general-engineering tasks include maintaining and improving LOC, constructing and repairing support facilities, and constructing airfields and aircraft support facilities.

TOPOGRAPHIC ENGINEERING

During the preparation phase, terrain analysts help the commander understand the terrain thoroughly and identify the military advantages and disadvantages. Engineers are the terrain experts. They tie into the IPB in several ways. Specifically, engineers provide information on terrain analysis and overlays with details on cover and concealment, lines of sight, cross-country movement, and LOC capabilities. They also assist in selecting battle positions and EAs and road and bridge classification products.

As the terrain is modified (bridges destroyed, roads built), the terrain team updates its data base and issues new products. Necessary information is reported through engineer channels. Topographic production facilities update maps with current information based on terrain modifications. This is generally done by overprinting existing maps. Other information, such as logistics data, planned obstacles, or tactical graphics, can also be overprinted directly on maps. Survey teams prepare the battlefield by establishing a dense network of control points to support artillery operations. They also perform airfield navigation surveys in support of Air Force units operating in the battle area.

PLANNING ENGINEER OPERATIONS IN THE DEFENSE

Engineers prepare for defensive operations using the tactical-planning process. Planning considerations specific to the defense include¯

MISSION, ENEMY, TERRAIN, TROOPS, AND TIME AVAILABLE

 The engineer must consider the factors of METT-T when planning engineer support for defensive operations:

Mission

The specifics of the mission will dictate the requirements for engineer support. A unit conducting an economy-of-force mission may require additional engineer support to allow it to complete its mission. A unit with a requirement to retain terrain will require significant countermobility and survivability support. As a final example, a requirement to conduct, or support, a counterattack will require breaching assets.

Enemy

The engineer is the expert on enemy engineer capabilities and works with the S2 to advise the maneuver commander on templating the likely enemy engineer COA, types and locations of key enemy breaching equipment, and enemy mobility organizations. The engineer must also contribute to the R&S effort to help develop PIRs.

Terrain

The engineer provides key products to assist the planning process. Examples include mobility-corridor obstacle overlays, road and bridge classification maps, and line-of-sight diagrams for key defensive positions. Using observation and fields of fire, cover and concealment, obstacles, key terrain, and avenues of approach (OCOKA), the engineer must be able to advise the maneuver commander on the advantages and disadvantages of each piece of terrain from the friendly's and enemy's points of view.

Troops

The engineer must have precise accountability of all personnel and equipment available, to include combined, joint, and HNS assets. During initial planning, the engineer must aggressively assist the task organization decision-making process. Unit and equipment assignments are critical to ensure proper command and support relationships throughout the conduct of the defense.

Time Available

After receiving the WO, the engineer must establish a time line. Depending on the amount of time available, he may choose to plan in a deliberate, combat, or quick manner. Planners must include all critical events on this time line, including OPORD issue, rehearsals, and precombat inspections.

TASK ORGANIZATION

The engineer commander and staff need to determine quickly the scheme of engineer operations that best supports the maneuver commander's intent. In anticipation of the defense, efficient use of available time demands establishing and linking up engineer units and equipment with their supported elements early.

The engineer recommends the best command or support relationship to the maneuver commander. Normally, the majority of engineers are placed in DS or GS of the defending forces. This allows efficient allocation of engineer resources and allows engineers to mass on the critical defensive tasks. Frequently, engineer planning HQ will link up with maneuver forces and conduct planning and coordination. Meanwhile the subordinate elements of the HQ are committed to supporting priority efforts elsewhere.

Although engineers are not held in reserve, they must be available to provide support to maneuver reserves or counterattack forces. These engineers will initially support defensive preparations and then support the reserve or counterattack force as a follow-on mission. They will require sufficient time to link up, plan, refit, and rehearse before executing the follow-on mission. Depending on METT-T, this will probably require 12 to 24 hours.

PREPARATION

When preparing for combat in the defense, engineer involvement is proactive at all levels. Immediately after receiving the WO, engineer staffs prepare an estimate and initiate movements and linkups, as necessary. Continual use of WOs keeps subordinates informed and current in the preparation process. Immediate precombat inspections identify any shortcomings and initiate necessary corrective steps, such as equipment maintenance. CSS planning is just as important and is integrated throughout the orders process. Class IV and V points are planned and established early. The staff also determines the availability and capability of resupply assets.

ENGINEERS IN THE DEFENSE

The mobile defense and the area defense are the characteristic patterns of defensive operations. The defense actually employed usually combines elements of both. For simplicity, they will be discussed separately.

MOBILE DEFENSE

A mobile defense orients on destroying the enemy force by using a combination of fire and maneuver, offense, defense, and delay to defeat the attack. It focuses on destroying the attacker in the depths of the defensive sector through the use of counterattacks. Defenders place minimum forces forward, forming powerful forces with which to strike the enemy at its most vulnerable time and place. The striking force can be from one-half to two-thirds the size of the total force, but it must have greater mobility than the attacker.

Because the defense involves significant battlefield maneuver, engineer forces focus on mobility operations. Engineers positioned with the counterattack force are reinforced with breaching and gap-crossing assets. They are prepared to reduce or cross existing obstacles such as railway embankments or rivers. They coordinate passage through lanes and prepare to breach friendly obstacles. They also prepare to breach enemy obstacles emplaced by air, artillery, or ground means. Engineers construct combat roads and trails to allow friendly forces in defensive positions to reposition from one position to another.

The successful mobile defense depends on the correct integration of maneuver, fire, and obstacles to wrest the initiative from the attacker in the defended area. Tactical obstacles are used to disrupt and delay enemy forces and to assist in the separation of echelons. Engineers also play a major role in establishing the conditions for the counterattack. They construct tactical obstacles to turn the enemy into engagement and objective areas and fixed obstacles to support the enemy's destruction by fires. Obstacle restrictions are common to protect the friendly forces freedom of maneuver. Other obstacle-control measures are smaller and less permissive for the same reason.

Engineers assist in developing survivability positions in depth. Repositioning units will require numerous fighting and protective positions. Because there will rarely be enough engineer assets, and therefore less survivability positions than desired, the most critical positions must be identified and constructed. Protective obstacles will be more important in protecting base clusters against rear threats, as forward units will likely move before the enemy's assault.

A decentralized engineer force distributed among the maneuver elements allows commanders the necessary flexibility. The engineers may have a command relationship with the supported maneuver forces.

AREA DEFENSE

Commanders conduct an area defense to deny the enemy access to designated terrain or facilities for a specified time. They retain terrain by drawing the enemy into an interlocked series of positions from which fire can destroy it. The bulk of the defenders fight forward in well-prepared defensive positions, with only small mobile reserves. The reserve in an area defense will be up to one-third of the entire force.

Preparing for an area defense is key, and the engineer effort is extensive. Retaining centralized control over engineer units and their resources is the most efficient method to prepare the area defense. Therefore, engineers generally are employed under their own commanders in a support relationship to maneuver forces. Once the battle is joined, a minimal number of engineers remain with the committed forces in a command relationship to allow rapid repair of obstacles and fighting positions and to provide support for local counterattacks. The bulk of the engineers withdraw to work on subsequent defenses in depth.

Tactical obstacles are used to force the enemy into EAs. Other tactical obstacles not only fix the enemy in the EA but also block his further advance. Additionally, obstacles are used to block the enemy from using AAs that will allow him to avoid the main defense. Disrupting obstacles are used just forward of EAs to fragment the enemy force and allow the defender to deal with only a small portion of the enemy at a time. The obstacle-control measures are used as permissive as possible to ensure that the subordinate commanders have the freedom to integrate extensive obstacles with their fire and maneuver.

Fighting and protective positions are more deliberate, and supplementary and alternate positions are more prevalent, in a mobile defense. Dismounted infantry will construct fighting positions able to withstand artillery attacks. Protective obstacles will be dense and interlocked around, and within, battle positions to help defeat the enemy's final assaults. Because defending forces will likely occupy their positions for longer periods of time, camouflage becomes increasing important.

On occasion, maneuver commanders may direct constructing a strongpoint to deny key terrain to the enemy and force its movement in a different direction. Constructing a strongpoint requires considerable time and engineer support. Generally it takes an engineer unit of the same size as the defending unit, working for one day, to create a strongpoint.

TRANSITION TO THE OFFENSE

Gaining the initiative and employing offensive operations are vital to victory. Opportunities are actively sought throughout the defense to transition to the offense. Employing obstacles in zones and belts, consistent with the commander's intent, permits free maneuver and allows offensive operations to occur rapidly. Engineers are task-organized throughout the maneuver organization to assist rapid deployment from defensive positions and through battlefield clutter when the enemy attack has reached the culminating point. Engineers at all levels plan for the transition to the offense as the sequel to a successful defense. They ensure that the engineer structure is designed to provide the necessary movement.



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