text: Operations During Armed Conflict
  (See ATP 3-90.8 for more information on countermobility.)
  MOBILITY OPERATIONS
  6-165. Freedom to move and maneuver within an operational area is essential to applying combat power.
  Most operational environments and enemy forces present numerous challenges to movement and maneuver.
  Leaders overcome these challenges through the integration of combined arms mobility.
  6-166. Mobility tasks are those combined arms activities that mitigate the effects of obstacles to enable
  freedom of movement and maneuver (ATP 3-90.4). There are six primary mobility tasks:
  (cid:122) Conduct breaching.
  (cid:122) Conduct clearing (of areas and routes).
  (cid:122) Conduct gap crossing.
  (cid:122) Construct and maintain combat roads and trails.
  (cid:122) Construct and maintain forward airfields and landing zones.
  (cid:122) Conduct traffic management and enforcement.
  6-167. Mobility tasks enable friendly forces to move and maneuver freely on the battlefield. Effective
  execution of mobility tasks depends on information collection and intelligence. Breaching and gap crossing
  in support of maneuver are primarily conducted using combat engineer units, often during close combat.
  6-168. Gap crossing, clearing, and the construction of combat roads and trails, forward airfields, and landing
  zones primarily support movement and require combat and general engineering units. Mobility tasks in
  support of movement are not normally conducted under fire, although the threat of fire is always present.
  6-169. A breach is a synchronized combined arms activity under the control of the maneuver commander
  conducted to allow maneuver through an obstacle (ATP 3-90.4). A successful obstacle breach is a
  synchronized and rehearsed combined arms activity under the control of the maneuver unit. Breaching is a
  mission undertaken to penetrate an obstacle. Breaching facilitates penetrations through enemy reinforcing
  obstacles covered with direct and indirect fire.
  6-170. Clearing is a mobility task that involves the total elimination or neutralization of an obstacle that is
  usually performed by follow-on engineers and is not done under fire (ATP 3-90.4). It is generally
  accomplished by destroying, altering, or removing obstacles.
  6-171. A gap is a ravine, mountain pass, river, or other terrain feature that presents an obstacle that may be
  bridged (ATP 3-90.4). Gaps will exist in an operational environment and present a significant challenge to
  movement and maneuver. A gap crossing is the projection of combat power across a linear obstacle (a wet
  or dry gap).
  SECTION II – DEFENSIVE OPERATIONS
  Even in the defensive position awaiting the enemy assault, our bullets take the offensive.
  So the defensive form of war is not a simple shield, but a shield made up of well-directed
  blows.
  Carl von Clausewitz
  6-172. Defensive operations defeat an enemy attack, buy time, economize forces, hold key terrain, or
  develop conditions favorable for offensive operations. Although offensive operations are usually required to
  achieve decisive results, it is often necessary, even advisable, to defend. Defensive operations alone do not
  normally achieve a decision unless they are sufficient to achieve the overall political goal, such as protecting
  an international border.
  PURPOSE AND CONDITIONS FOR THE DEFENSE
  6-173. One purpose of defending is to create conditions for the offense that allows Army forces to regain
  the initiative. Other reasons for conducting the defense include—