text: Security Operations
  PASSAGE OF LINES (FORWARD AND REARWARD)
  5-155. Cavalry units usually begin and end reconnaissance and security operations with a passage of lines,
  or a reconnaissance handover (discussed in chapter 4). A passage of lines is a tactical operation designed to
  pass one unit through the positions of another unit without interference. A passage may be designated as a
  forward or rearward passage of lines. A passage of lines is an inherent aspect of transferring responsibility
  for the battle between commanders while maintaining continuity of the fight. Cavalry units can be the passing
  or stationary force.
  FORWARD PASSAGE OF LINES
  5-156. A forward passage of lines occurs when a unit passes through another unit’s positions while moving
  toward the enemy (ADP 3-90). Cavalry units conduct forward passage of lines as a transitional operation,
  typically before reconnaissance and security missions, when the factors of METT-TC (I) do not provide the
  freedom of bypassing a forward friendly unit. A forward passage of lines may also be conducted by Cavalry
  units to—
  * Continue the attack or counterattack.
  * Envelop a threat force.
  * Pursue a fleeing threat.
  * Pass between friendly areas of operations during nonlinear operations.
  5-157. The passing force uses two techniques. In the first technique, the passing force deploys in its attack
  formation in the attack positions to the rear of the FLOT and crosses the FLOT in attack formation. This
  technique is appropriate if there is adequate maneuver space for the passing force to deploy effectively and
  without disrupting the stationary force’s defensive positions. This technique also allows the passing force to
  rapidly attack once it crosses the FLOT.
  5-158. In the second technique, the passing force deploys after crossing the FLOT. Using this technique,
  the passing force crosses the FLOT in march column and then deploys into attack formations prior to crossing
  the BHL. This technique is required by restrictive terrain. If this technique is used, the FLOT should be
  outside direct fire range of the threat to allow the passing force to deploy before making direct fire contact
  with the threat.
  5-159. Both of the passing force’s techniques require stationary unit scouts on or near the BHL. The passing
  unit may have their scout platoon link up with stationary unit scouts and continue the mission or they may
  have combat units deploy along the BHL to overwatch movement of other units. The units on the ground at
  the BHL must know the scheme of maneuver of the passing force so that they can act accordingly.
  5-160. If the stationary unit identifies a gap or weak point in the threat's deployment, they should go about
  identifying axes of attack for the passing force that take advantage of that weakness (reconnaissance-pull).
  The premier consideration is that the stationary force should not pass the moving force into the teeth of the
  threat defense. The passing force must be flexible enough to modify its scheme of maneuver, if necessary, to
  take advantage of weaknesses in the threat’s defense. Figure 5-18, page 5-44 depicts the graphic control
  measures associated with a forward passage of lines.