text: Chapter 16
  to displace artillery assets during critical stages of the passage. Ideally, enemy forces have not previously
  identified these positions.
  16-26. Detailed air and missile defense planning is essential. Passing units tend to move slowly and often
  in some type of column formation during their passage. Passing and stationary unit vehicle congestion
  presents lucrative targets to enemy aircraft and missiles. Dissemination of early warning and airspace control
  information reduces the risk of fratricide to friendly aviation assets while increasing the probability of the
  timely detection of enemy aircraft and missiles. Strict weapons control status among pilots and air and missile
  defense units is critical, especially during limited visibility.
  SUSTAINMENT AND PROTECTION
  16-27. Stationary forces furnish passing forces with necessary assistance (within their capabilities) as far
  forward as possible, but behind the BHL. Staffs can coordinate this assistance in advance or provide it on an
  emergency basis. The types of assistance typically provided includes—
  * Evacuating casualties and detainees.
  * Using areas and facilities such as water points and medical facilities.
  * Controlling routes and traffic management.
  * Recovering disabled vehicles and equipment.
  * Controlling dislocated civilians.
  This assistance expedites the passage of lines.
  FORWARD PASSAGE OF LINES
  16-28. The purpose of a forward passage of lines is to move forces forward to conduct offensive operations.
  Units performing forward passages of lines maintain enemy contact while allowing the relief of previously
  committed forces. Stationary units control and secure their assigned areas far enough to their front that
  moving units can pass through them and deploy into movement formations prior to those moving units
  making enemy contact. Generally, stationary units support passing units with direct fires until those passing
  units mask those direct fires. Stationary units continue providing fire support to passing units until those
  passing units move beyond the range of those systems. Stationary units secure the lines of departure of
  forward passing units until these later units can assume those responsibilities. The boundaries of forward
  passing units after they complete their passage do not have to coincide with the boundaries of stationary units.
  Figure 16-2 depicts a forward passage of lines.