text: Countermobility
  Note. As of 1 January 2011, U.S. forces are no longer authorized to employ persistent (those that
  are not self-destructing or self-deactivating) or nondetectable land mines.
  * Networked munitions. Networked munitions are remotely controlled, interconnected, weapons
  systems designed to provide rapidly emplaced ground-based countermobility and protection
  capability through scalable application of lethal and nonlethal means (JP 3-15).
  * Demolition obstacles. Demolition obstacles are created using explosives. Examples include
  bridge or other structure demolition (rubble) and road craters. (See ATP 3-90.8/MCTP 3-34B for
  more information on demolition obstacles.)
  * Constructed obstacles. Constructed obstacles are created without the direct use of explosives.
  Examples include wire obstacles, antivehicle ditches, or similar construction that typically
  involves the use of heavy equipment. (See ATP 3-90.8/MCTP 3-34B for more information on
  constructed obstacles.)
  17-11. The use of some obstacles, specifically mines, is governed by U.S. law, U.S. policies, and
  international treaties or agreements. The United States regards mines as lawful weapons when employed
  according to accepted legal standards. These laws and policies are complex and subject to change; therefore,
  it is essential that commanders coordinate with legal advisors when developing local rules of engagement
  (ROE) and ensure that legal advisors review law and policies for legal sufficiency. (See JP 3-15 for more
  information on the laws, agreements, and policies that are most significant to the employment of obstacles.)
  TACTICAL OBSTACLES
  17-12. The primary purposes of tactical obstacles are to shape enemy maneuver and to maximize the effects
  of fires. Tactical obstacles directly attack the ability of a force to move, mass, and reinforce; therefore, they
  affect the tempo of operations. Units integrate obstacles into the scheme of maneuver to enhance the effects
  of fires. Preexisting obstacles that a unit reinforces and integrates with observation and fires may become
  tactical obstacles. The types of tactical obstacles are clearly distinguished by the differences in execution
  criteria. The three types are—
  * Directed obstacles.
  * Situational obstacles.
  * Reserved obstacles.
  17-13. A directed obstacle is an obstacle directed by a higher commander as a specified task to a subordinate
  unit (ATP 3-90.8/MCTP 3-34B). The higher commander directs and resources these obstacles as specified
  tasks to a subordinate unit. Units plan, prepare, and execute directed obstacles during the preparation of the
  area of operations. Most tactical obstacles are directed obstacles.
  17-14. A situational obstacle is an obstacle that a unit plans and possibly prepares prior to starting an
  operation but does not execute unless specific criteria are met (ATP 3-90.8/MCTP 3-34B). Situational
  obstacles are preplanned obstacles as part of a TAI. They provide the commander with flexibility for
  emplacing tactical obstacles based on battlefield development.
  17-15. A reserved obstacle is an obstacle of any type, for which the commander restricts execution authority
  (ATP 3-90.8). The commander specifies a unit that is responsible for preparing, guarding, and executing
  reserved-obstacle emplacement. Units execute reserved obstacles only on command of the authorized
  commander or based on specific criteria identified by the commander. The purpose of a reserved obstacle is
  to retain control over the mobility along an avenue of approach. Commanders use reserved obstacles when
  failure to maintain control over the mobility along an avenue of approach will have disastrous effects on the
  current battle or future operations.
  PROTECTIVE OBSTACLES
  17-16. Protective obstacles are employed to protect people, equipment, supplies, and facilities against
  threats. Protective obstacles have two primary roles, defense and security: