The use of smoke-producing devices has been highly developed during the war, with an increasing realization as to the importance of the results thus secured for a large variety of military operations. The improvements throughout the conflict have been continuous and extraordinarily effective. Chief among the employments to which this sort of device is peculiarly suited are the following:
1. To increase the visibility of explosions for shells of either small or average caliber, as an aid in determining the exact range.
2. To neutralize an enemy battery, or to conceal observation posts at great distances.
3. To hide enemy shelters and different organizations near at hand.
4. To simulate the effect of either rifle firing or the discharge of shells, in order to deceive the enemy.
5. To screen important organizations or movements of troops from view of the enemy.
As to the first of these employments, it must be borne in mind that explosive shells on bursting give off smoke from only a small quantity of black powder. This is not very distinctly visible, and, too, it is dissipated rapidly. On this account, it is of advantage often to increase the visibility of such explosions by the use of some additional material that shall supply a larger volume of smoke with sufficient density. For this purpose, the smoke-producing material most frequently used is red phosphorus, to which arsenic may be added. The arsenic may be either free or in combination. Paraffin serves as a casing for the phosphorus, and protects it against dampness. This material is ordinarily inclosed in a cardboard cylinder, to which the name unter Korper is given. It is buried in the explosive charge.
By this means, at the time of the shell's exploding, an abundant white smoke is thrown off. When arsenic is used, the smoke has the powerful alliaceous odor characteristic of this substance. Shells equipped with such a smoke-producing device are of especial value for establishing the range. It suffices that only a certain proportion of the explosive shells should be provided with the contrivance. The proportion is usually one-third for field guns, but one-half for the light 105 millimeter howitzer. The shells bear distinctive markings.
The Germans, on occasion, made use of a gray smoke, which was produced from a heavy carbonated powder with impure tolite (T. N. T.). The composition used for this purpose in a 105-millimeter explosive shell had a weight of 100 grams, made up as follows:
Carbon and bitumen ....................
Impure tolite (T. N. T.) approximately......................
Not measured ..........................
It seems probable that this gray smoke was employed for the sake of establishing the range, while a smoke screen was being used to hide both the objective and the explosions. The explosions producing the gray smoke were distinctly visible, since the color stood out in sharp contrast to the white of the screen.
As to the second employment of such smoke-production - for the neutralization of an enemy battery or observation post at a distance - the composition of the special charge in the shells includes tolite, carbon, bitumen, and sodium nitrate, or it may be a mixture of sulphureted arsenic and potassium nitrate.
For the third employment of smoke-producing devices - the hiding of enemy shelters or other organizations near by - 9-centimeter trench projectiles are commonly employed, or projectiles in containers of cardboard, or special grenades. When a very close approach can be made, tubes charged with a composition that is both incendiary and smoke-producing are effective.
The smoke candle was found to be of especial value for use in trench and field warfare whenever a small compact article was required. In the construction of these, three pounds of smoke mixture are packed within a tin container. The kindling of the composition is by means of the match-head type of ignition. A uniform volume of smoke is given off for a period of four minutes, which lies in a thick, foglike cloud, close to the ground. The smoke has the great advantage of being perfectly harmless, so that it may be breathed without discomfort. Its power of obscuration is extremely high.
Phosphorus has been found the best available substance for smoke barrage. A common type contained a mixture in a tin case, of which the dimensions were 5 by 3 inches. The mixture was of red phosphorus lumps, 70 parts, with red phosphorus powdered, 11 parts. This was fired either by a detonator, or a time fuse. Grenades for use by hand or by rifle contained molten white phosphorus in a quantity of 12 1/2 ounces. These grenades also were fired by either a detonator or a time fuse, set for 6 1/2 seconds. Where a supply of phosphorus was lacking, effective substitutes were found in various other substances.
Perhaps the most interesting single development of pyro-techny in the war was the use of rockets similar in type to those over which military experts waxed so enthusiastic 100 years ago. Thus, the Germans followed Congreve's construction in the use of metal, but modified the type in order to eliminate the necessity for a stick. Over a century ago, various attempts were made to do away with the stick attached to the rocket, but the results were never wholly satisfactory. The usual method was by dependence on holes pierced in the case, for the escape of gas in such a manner as to impart a rotary movement to the rocket, forcing a direct flight forward. In Hale's rocket,1 the added apertures for such escape of gas were made in the forepart of the firework. In the German war rocket, however, the openings for the escape of gas were in the base. It is sufficient to add that the Germans were not alone in endeavoring to utilize this principle by which the stick might be eliminated in the construction of war rockets. It is reasonable to believe that such a method of construction, long ago accepted with enthusiasm, may ultimately be revised and perfected.
It should be noted that the British, by reason of the efficiency attained with other forms of fireworks, were able in the last months of the war to discontinue the use of rockets. This, however, was a measure of economy, rather than of preference. As a matter of fact, the war has demonstrated once again the unique merits of the rocket - carrier of its own projecting mechanism.
Certain novelties of a pyrotechnic sort showed themselves during the conflict, some of great value, others of doubtful worth. Thus, the Italians developed a hissing flare,1 which, while suspended from a parachute, burned with a hissing noise distinctly audible over an area 3,000 meters in diameter. This was found practically effective as a gas alarm.
1 See appendix.
Both British and Italians successfully employed the rocket stick as a message carrier. The message (or map) was contained in a metal tube fastened at the lower end of the stick. In combination with this was a smoke bomb, which was set burning when the stick struck the ground. The plume of smoke from the bomb marked the resting place of the message.
The British experimented with an aerial flare to be used for illuminating enemy aircraft while in flight. This was designed to float with a parachute and to cast its cone of radiance upward. Great difficulty was experienced in securing adequate reflection of the light rays, and the contrivance had not been perfected at the conclusion of hostilities.
It would be impossible within the limits of this space to enumerate all the diverse forms of fireworks exploited by the various belligerents during the war. The details already set forth are sufficient to indicate in some degree both the importance and the novelty of the aspects under which pyro-techny has been demonstrated in the exigencies of conflict.1
It is a far cry from the flubdubbery of primitive priests and magicians to the amazingly effective displays of art in aerial fires over the blood-drenched fields of Europe. The grim needs of war incited all the combatants to strenuous effort for the enlarging and strengthening of their skill in pyrotechny. The end of the struggle shows a fireworks construction marvelously developed in many phases, yet to a considerable extent incomplete, in some directions confused, in others probably worthless. Under the less-hurried conditions of peace, the nations will now test their achievements with a discrimination that must finally determine the usefulness of every device, its essential practicality. Thus, we may believe that, presently, the art of pyrotechny will attain to scientific precision throughout its vastly broadened scope, a precision to which it has never reached in its more meager past. Moreover, there is the blessed assurance that, with pyrotechny as with all else, lessons learned under the scourge of war shall yet serve beneficently the gentler arts of peace.
1 Various types are summarized in the appendix.