c. As enemy forces approach friendly defensive positions, the smoke unit can produce hasty
smoke screens to channel enemy forces into restrictive terrain or prearranged ambush areas. A
combination of smoke, obstacles, and indirect fires will accomplish this channeling. The smoke screen
also serves to conceal obstacles and minefields from enemy observation.
d. During the defense the momentum of the enemy attack may force friendly units to fall back
to successive defensive positions. The smoke unit can support this action by concealing friendly units
during this move and by creating a smoke blanket in the main battle area to reduce the speed of
attacking enemy forces.
e. Smoke units can support the reserve force by concealing location or by producing a flank
smoke screen to hide the reserve force as it maneuvers into the main battle area to begin its attack.
f. Smoke may also be used in the defense to conceal rear-area support units. The ability of
these units to provide supplies and equipment to the defense sustains the firepower of defending units.
Smoke units can conceal rear-area support units as well as major supply route features.
g. The mission of smoke support during the defense is to engulf the enemy in smoke without
degrading friendly operations. Smoke support in the defense requires constant attention to wind
direction and weather conditions. A successful defense is fought on the terms of the defending force.
Well-planned and well-executed support by the smoke unit degrades enemy maneuver, command and
control, and ability to use major weapon systems; it also degrades the capability of the attacking enemy
to dictate the battle. This degradation of enemy capabilities gives the initiative to the defending force,
enhancing the overall success of the defense.
h. During the offense or defense one unit may pass through another unit to fall back and allow
fresh units to maintain the defense or push forward to conduct an attack. This is called a passage of
lines. Smoke units can support the passage of lines by concealing those points where the units pass
through each other or by concealing the rear unit from enemy observation. Concealment of the rear unit
denies the enemy intelligence as to the unit's presence, which may cause the enemy to overextend its
attack or to launch a counterattack prematurely. Figure 1-24 illustrates the use of smoke to support a
passage of lines.