To conceal emplacing of minefields or barriers.
To conceal airstrips or helicopter pads.
To conceal relief of combat units.
To channel enemy troops or vehicles into ambush sites.
(3) Deceptive Screens. A unit can use the M157/M998 to produce either large-area or small-
area deceptive smoke screens. Like the M1059, the M157/M998 gives credence to the deceptive smoke
screen by maneuvering while producing the smoke screen; the engine sound of the M113A2 may be
interpreted as indicating the presence of mechanized vehicles.
c. Limiting Factors. Any of several factors can limit the production of effective smoke screens.
The five major limiting factors affecting the M157 Smoke Generator System are maneuver conditions
(mobile smoke only), wind, weather, terrain, and fuel and fog oil supply. Discussion of these conditions
(1) Maneuver Conditions. This limiting factor applies only to the production of smoke while
the M1059 or M157/M998 is moving. The presence of smoke reduces visibility; therefore, it limits the
maneuverability of smoke vehicles. For the M1059 and M157/M998 this means that the vehicles must
reduce their speed once the smoke screen builds up. Also, the presence of other vehicles maneuvering in
the smoke screen further reduces the ability of the M1059 or M157/M998 to maneuver freely and to
react to changes in the mission or in the smoke screen. During smoke operations when the M1059 or the
M157/M998 is maneuvering in the smoke screen with other vehicles, it is imperative that all vehicle
maneuver routes be planned, coordinated, and disseminated to all soldiers involved. Furthermore, the
presence of enemy fire in the area forces mechanized vehicles to close all hatches, further reducing
The remaining four limiting factors affect smoke once it has been produced. Smoke screens from
stationary smoke generators may extend 1.6 to 6.4 kilometers (1,600 to 6,400 meters) from the smoke
source, depending on these factors. Discussion of these four limiting factors follows.
(2) Wind. Steering winds, which are found between 9 and 800 meters above the ground,
have the greatest rind influence on smoke. Once released, the smoke moves to the level of the steering
winds and follows their course. Wind speed does not affect the level of the steering winds but does
determine the distance the smoke must travel before reaching the level of the steering winds.
Turbulence influences the height of the steering