Conditions naturally vary, but observers report that smoke can often be used effectively. Some difficulties with the use of smoke are caused by desert winds, which are sometimes quite variable. Different sizes of whirlwinds which veer and change direction constantly make it difficult to estimate the wind when laying a smoke screen. Smoke has, however, many possibilities in connection with operations by armored formations.

a. Characteristics

Three main factors affect the use of smoke in the desert as elsewhere:

(1) The force and direction of the wind.

(2) Turbulence (which is the gustiness of the wind) and the effect of the bright sun on air currents.

(3) Humidity.

These factors do not remain constant, the force and direction of the wind being particularly liable to sudden change. Moreover, air eddies caused by the configuration of the ground may make the force and direction of the wind different at the spot where shells land and at the gun position. It is therefore impossible to specify particular weather conditions in which smoke will be effective. A decision on this point is reached usually by a method of trial and error, for which time must be allowed.

In desert areas high-explosive shell produces a substantial cloud of dust, and it may therefore often be practical to mix HE with smoke and so produce a satisfactory screen when conditions are not entirely suitable for the use of smoke alone. This fact also makes it possible to economize in the use of smoke shell and bombs, only limited quantities of which are usually carried.

b. Tactical Employment

All antitank guns depend on direct observation to obtain fire effect. If they can be deprived of their observation, their fire is automatically neutralized. In this fact lies the greatest value of smoke, particularly to armored divisions.

In attacks smoke has been used for the following purposes:

(1) To conceal local preparatory moves by supporting weapons such as antitank guns, machine guns, and mortars.

(2) To screen a forward movement preparatory to assault.

(3) To screen tanks from the observation of antitank guns and artillery observation posts on the flanks of the attack.

(4) To provide a smoke barrage on the front of the attack.

(5) To indicate the objectives to tanks.

Smoke screens required during the preparatory stages of the attack and during the advance to the objective are usually provided by the artillery. Assistance is sometimes given by infantry mortars when other tasks and the range permit. For a smoke barrage on the front of the attack, a crossing wind is necessary, and particular attention is paid to timing to insure that the attacking tanks are not placed in the dilemma of having either to wait for the barrage to lift, or to pass through it with the risk of being silhouetted against it on the far side.

In any attack some guns are either not located or not destroyed. In such situations some advantage has been obtained by smoke clouds laid down over the whole area,¹⁷ for the lack of visibility usually hampers the guns more than the tanks. This smoke is not used to form a screen, for it is considered more effective to form a pall of smoke over the enemy defensive area.

In defense situations smoke is used to blind attacking enemy tanks. When used for this purpose, a smoke screen is put down beyond the effective antitank range. Otherwise it will merely assist the enemy by depriving the antitank guns of essential observation. The provision of a smoke screen of this kind usually is a task for the artillery.

German tanks in a hull-down position at over 2,000 yards' range are not only difficult targets, but also beyond the effective range of antitank guns. Much of the Axis fire is by direct laying. In many cases, therefore, the best method of dealing with Axis fire has been by a smoke screen. Care is then taken that this smoke screen is well clear of the British front lines, for if it is too close, it will merely serve as cover for the German advance.

While the smoke is in place, Axis unarmored troops are attacked by fire. Observation posts well out to a flank are found to be necessary, and every opportunity is taken to disorganize and cause casualties to the enemy while he is assembling for the attack.

Another use of smoke in the defense has been the blinding of the enemy's close-support tanks and other supporting weapons by interposing a smoke screen between them and the enemy assault tanks. This task may be within the power of both the defenders' close-support tanks and artillery. When smoke was used for this purpose care was taken to avoid assisting the enemy by providing him with cover behind which he could move forward infantry detachments in support of his assaulting tanks.

For covering a disengagment or a withdrawal, all types of smoke-producing weapons are used, smoke screens at the longer ranges being put down by the artillery, medium range screens by close-support tanks, and short range screens by the use of special dischargers and 2-inch bomb throwers. Tanks capable of producing tail smoke have also been used effectively for this purpose by both the Germans and the British.