FM 3-34.22 - Army Electronic Publications & Forms - U.S. Army

Chapter 6
Mobile Defense
6-89. Mobile defense focuses on defeating or destroying the enemy by allowing advancement to a point
where it is exposed to a decisive counterattack by the striking force. Mobile defense uses a combination of
offensive, defensive, and delaying actions. It is characterized by relatively small, fixing forces forward and
the use of maneuver supported by obstacles to take the initiative. Mobile defense requires a large striking
force with mobility equal to or greater than that of the enemy to counterattack and defeat the enemy force.
6-90. Engineer support to a mobile defense focuses on using obstacles to attack enemy maneuver and
providing mobility to the striking force and reserve. Most countermobility and survivability assets support
the fixing force, while most mobility assets support the striking force. Obstacle zone planning received
from the division and obstacle belt planning at the brigade level are directed at the most likely enemy COA
rather than the terrain. Belts are aimed at enemy maneuver in the brigade AO to support its destruction by
counterattack. Therefore, obstacle belt planning is more restrictive to assure the mobility of the striking
force. Situational obstacles are advantageous in the mobile defense by allowing the commander to exploit
enemy vulnerabilities, exploit success, separate follow-on forces, and provide flank protection.
6-91. The survivability effort is uniquely tailored in a force-oriented defense. To create the conditions for a
counterattack, battalions may need to fight throughout the depth of their AO using multiple primary and
subsequent BPs. Protective obstacle effort may occur at any point within the mobile defense, though
minimal protective-obstacle effort may be required forward as the defense is geared toward a proactive
fight. The protective-obstacle effort and, typically, the supporting fighting-position effort are concentrated
where enemy penetration must be stopped to allow the counterattack to take place. Obstacle control
measures ensure that battalion obstacle efforts do not affect strike force ability to maneuver.
Area Defense
6-92. Area defense denies enemy access to specific terrain for a specific time. It is organized to absorb the
enemy into an interlocked-series of positions from which it can be destroyed. Area defense differs from
mobile defense in that most defending forces are committed to defending positions while the rest is kept in
reserve. To accomplish this, forces use a combination of defensive positions and small mobile reserves.
Commanders organize the defense around the static framework provided by defensive positions, seeking to
destroy enemy forces with interlocking fires or local counterattacks that are focused on EAs.
6-93. The commander organizes an area defense by designating his MBA and assigning AOs, BPs, or both
to subordinate units located within the MBA. He also creates a security area in front of the MBA. In
planning an area defense, the commander can organize a defense in depth or a forward defense based on
where defensible terrain is within assigned AO (terrain characteristics), the chosen enemy COA estimate,
and the other METT-TC factors. (See FM 3-90, FM 3-90.5, and FM 3-90.6 for more information.)
6-94. A defense in depth is the preferred option when the tactical conditions allow. It limits the enemy’s
ability to exploit a penetration through additional defensive positions employed in-depth. Alternate and
supplementary positions, combat outposts, and mutually supporting strong points forward of the perimeter
extend the depth.
6-95. The intent of a forward defense is to prevent enemy penetration of the defense. Due to its inherent
lack of depth, the forward defense is the least preferred option. Commanders use a forward defense, when
directed, to retain forward terrain or when the terrain (strong natural obstacles) favors a defense in that part
of the AO.
6-96. The focus of the engineer effort is on providing the maneuver commander with the ability to hold
terrain while enabling maneuver units to concentrate fires from static positions. During area defense,
engineer involvement in terrain analysis is vital. Engineers help identify key and decisive terrain that
supports the commander’s concept of the operation, with a focus on where the commander wants to kill the
enemy. During obstacle planning, obstacle control measures are designed to give maximum flexibility to
subordinate units, while focusing the tactical obstacle effort on terrain retention. The ENCOORD must
advise the maneuver commander of the resource requirements of each subordinate unit based on its
assigned essential tasks for M/CM/S and must coordinate through the appropriate channels to ensure that
the units are resourced accordingly.
6-20 FM 3-34.22 11 February 2009