NOTES ON THE USE OF SMOKE.
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Smoke may be employed for two purposes:-
- To simulate gas. This may be useful when the supply of the latter is limited: intervals of smoke discharge could be interposed, especially under circumstances when it is desired to compel the enemy to wear their respirators continuously.
- To cover movements of Infantry. The discharge of a smoke cloud will probably always attract immediate attention and hostile fire.
This point should be considered so as to avoid isolated discharges on a short front; as if these are intended to conceal local movements of troops they will only serve to draw the attention of the enemy’s observers to spots on which the concentration of artillery and machine gun fire is likely to be well repaid.
Our present methods of producing smoke are as follows:-
- By Trench Mortar Shells.
- By Smoke Candles.
- By ‘P’ Bombs.
- By other extemporized methods, such as the burning of Phosphorus in open pans.
- For the present, at any rate, the 4” Stokes Mortars will be chiefly used for throwing smoke shells, and one of the Battalions of the Special Brigade has been carefully trained in the formation of smoke barrages in varying wind conditions, and in denying the power of observation to particular sections of the enemy’s position.
- Smoke candles as at present issued are of three types:-
- Pain’s Green Label. These candles burn well, and give a yellowish-brown smoke. They are the best at present issued. Average time of burning, 2 – 3 minutes.
- Wells’ Red Label. These are similar to pain’s, and burn for the same period, but they do not give such a good smoke: the latter is also of a lighter colour. The connections between the components of the triple candle are sometimes defective, and one or two sections are occasionally left unburnt.
- ‘Pelagus’ Yellow Label. These candles are very poor.
Fortunately there are very few available for issue.
Note: There may be other types of smoke candles in store – such as Brock’s: but these may be assumed to be similar in all important respects to (1) and (2).
In winds of greater velocity than 10 – 12 m.p.h. the smoke from all types of candles is of very little use, unless mixed with gas, except for obscuring the actual line on which the discharge takes place, and then only if the candles are used in considerable numbers.
- ‘P’ bombs give a very good cloud of smoke, but the greater part of the cloud is created on the bursting of the bomb. The thick cloud lasts for about one minute: for a minute or two afterwards, a fairly large volume of smoke continues to be produced, but after this the bombs are only about as effective as a Pain’s candle, although smoke continues to be discharged from them for 15 – 20 minutes altogether.
These bombs should not, if it can be avoided, be used on fronts over which Infantry are to advance to the assault, because the burning phosphorus left on the ground is a source of danger to men who may fall wounded; and during the summer months it may also set fire to the grass. The smoke from ‘P’ bombs is, however, so much better than that from candles that ity might be advisable to accept the risk mentioned under circumstances when it was essential to give infantry assaulting columns cover from view.
Men employed in lighting these bombs (fuzee matches should be provided) should be instructed to throw them as far forward as possible, preferably in front of our wire: otherwise the burning phosphorus may be scattered back into our trenches on the bursting of the bomb, or it may be splashed back, when lying on the ground, by the enemy’s shrapnel fire. This rule was not observed on October 13, and as a result reports were received from several points in the line to the effect that the Germans were employing incendiary shells against our trenches.
It was also observed on this occasion in some parts of the line that infantry charged with using the bombs had received no previous instruction in their duties, and as a consequence many of the bombs were thrown out unlit.
- Loose phosphorus can be easily ignited by means of safety fuze or safety fuze and detonator.
NUMBER OF CANDLES AND OF ‘P’ BOMBS TO BE EMPLOYED.
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Smoke Candles.
Numbers should be calculated with a view to producing a smoke cloud in a fairly high wind, namely, 10 – 12 m.p.h. Four candles per minute at each emplacement 25 yards apart, (i.e. 10 candles per yard of front per hour) should be allowed to give Infantry partial protection from view 200 yards in front of the line of candles.
Two candles per minute at each emplacement would conceal Infantry getting out of their trenches preparatory to the assault, but troops would be visible from in front after advancing 20 or 30 yards.
As the result of a chemical action, when mixed with gas the cloud becomes three or four times as effective as when candles are employed alone, and the number of the latter could be reduced in this proportion.
Of course it would not be necessary to maintain a dense cloud of smoke during the whole period of a gas attack: the smoke should be thickened up just before the time for the assault – and perhaps at one or two periods previously, so as not to disclose the intention.
‘P’ Bombs.
Sixty bombs per hour at each emplacement 25 yards apart (i.e. 2 bombs per yard of front per hour) would give a very effective smoke barrage in a moderate wind, and would conceal our men from the enemy in position 300 yards away until they were close up to them. Gas produces no appreciable effect on the density of the smoke from ‘P’ bombs.
May 15, 1916
C.W. Foulkes
colonel.
O.C., Special Brigade.
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