text: Defense
  conduct a forward defense,while the other part conducts a defense in-depth. The specific mission may also
  impose constraints such as time, security, and retention of certain areas, which are significant factors in
  determining how the BCT defends.
  Defense In-Depth
  7-127. A defense in-depth (see figure 7-11) reduces the risk of a quick penetration by the attacking enemy
  force. Even if initially successful, the enemy has to continue to attack through the depth of the defense to
  achieve a penetration. The defense in-depth provides more space and time to defeat the enemy attack.
  Dependent on the mission variables of METT-TC, it may require forces with at least the same mobility as
  the enemy to maneuver to alternate, supplementary, and subsequent positions. The mobility of the enemy
  force can determine the disengagement criteria of the defending forces as they seek to maintain depth. The
  BCT commander considers using a defense in-depth when—
  (cid:122) The mission allows the BCT to fight throughout the depth of the area of operations.
  (cid:122) The terrain does not favor a forward defense and there is better defensible terrain deeper in the
  area of operations.
  (cid:122) Sufficient depth is available in the area of operations.
  (cid:122) Cover and concealment forward in the area of operations is limited.
  (cid:122) CBRN weapons may be used.
  (cid:122) The terrain is restrictive and limits the enemy’s maneuver and size of attack.
  Figure 7-11. Defense in-depth