text: Chapter 17
  Countermobility
  Countermobility operations is a combined arms activity. This chapter addresses the
  general considerations for countermobility, terrain reinforcement, obstacle intent,
  obstacle employment principles, and obstacle emplacement.
  GENERAL COUNTERMOBILITY CONSIDERATIONS
  17-1. Countermobility is a set of combined arms activities that use or enhance the effects of natural and man-
  made obstacles to prevent the enemy freedom of movement and maneuver (ATP 3-90.8/MCTP 3-34B). The
  primary purposes of countermobility are to shape enemy movement and maneuver and to prevent the enemy
  from gaining a position of advantage. Countermobility directly supports offensive and defensive operations,
  but only indirectly supports stability and defense support of civil authorities tasks. Offensive and defensive
  operations are always combined with stability operations; defense support of civil authorities tasks are
  typically only performed in support of homeland defense.
  17-2. Countermobility can be confused with other tasks or activities that may also employ obstacles. An
  obstacle is any barrier designed or employed to disrupt, fix, turn, or block the movement and maneuver, and
  to impose additional losses in personnel, time, and equipment (JP 3-15). Antiterrorism, physical security,
  survivability, safety, and traffic operations often employ obstacles such as perimeter fencing, concrete walls,
  and vehicular barriers. However, only countermobility involves tactical obstacle employment with effects
  directly linked to tactical mission tasks. Another discernible difference of countermobility is that it is a
  combined arms activity conducted to directly support offensive and defensive operations, which may be
  combined with stability and defense support of civil authorities tasks.
  17-3. Countermobility enables combined arms forces to shape enemy movement and maneuver and prevent
  the enemy from gaining a position of advantage. In the offense, countermobility is conducted to help isolate
  objectives and prevent the enemy from repositioning, reinforcing, and counterattacking. It enables flank
  protection along an axis of advance or as an integrated economy-of-force effort to provide general flank
  security. In the defense, countermobility disrupts enemy attack formations and enables friendly forces to
  defeat the enemy in detail. Obstacles help channel the enemy into engagement areas throughout and protect
  the flanks of friendly forces conducting a counterattack.
  17-4. In support of offensive operations, countermobility may be required to defend a lodgment and protect
  selected sites and positions from which combat power must be generated and sustained. The unit’s options
  for emplacing reinforcing obstacles in the offense are often limited because of challenges in gaining early
  access to much of the assigned area. This increases the importance of taking advantage of existing obstacles
  and the natural restrictiveness of the terrain. It also increases the unit’s reliance on rapid obstacle
  emplacement capabilities, especially remotely delivered obstacles to reinforce the terrain.
  17-5. In support of defensive operations, countermobility operations use tactical obstacles to shape
  engagements and maximize the effects of fires and use protective obstacles to provide close-in protection
  around defensive positions. Protective obstacles help warn, prevent, and mitigate intrusion into critical fixed
  sites such as assembly areas and sustainment sites, or a final enemy assault onto a unit position. Erecting
  obstacles is also a critical supportive task to conducting denial operations. In the defense, earlier access to
  more of the assigned areas typically provides units with the time and information to consider a broader range
  of options for reinforcing the terrain. In addition to the rapid obstacle emplacement capabilities often used in
  the offense, units can often use more time- and resource-intensive techniques to reinforce the terrain for
  longer periods. This may or may not be the case in support of lodgments. Such techniques include mostly