As our Army was organized in France, and as it is organized at present, the number of 155 mm. guns will be greater than all others put together, except the 75 mm. In order that a non-persistent gas may be most effective a high concentration must be built up very quickly. This necessitates the use of the largest caliber shell that are available in large numbers. Of course, a certain percentage of the gas shell of other calibers may consist of non-persistent gases in order to help out the 155 mm. gun. This is in accordance with the present program for loading gas shell and applies particularly to the 8-inch and 240 mm. Howitzer.
Few Ideally Persistent or Non-Persistent Gases. Naturally there will be very few gases that are ideally non-persistent or ideally persistent. The groups will merge into one another. Those on the border line will be arbitrarily assigned to one group or the other. It might be said definitely, however, that a gas which will linger more than six or possibly eight hours under any conditions, except great cold, will not be considered non-persistent. For reasons of efficiency and economy persistent gases will not be chosen unless they will persist under ordinary conditions for two or three days or more. Accordingly, a gas which would persist for one day only would have to be extraordinarily useful to lead to its adoption.
Firing Non-Persistent Gases. Of the non-persistent gases phosgene is the type and the one most used at present. Furthermore, so far as can now be foreseen, it will continue to be the non-persistent gas most used. It volatilizes very quickly upon the bursting of the shell. Accordingly, in order that the shell fired at the beginning of a gas “shoot,” as they are generally referred to in the field, shall still be effective when the last shell are fired, it is necessary that the whole number be fired within two to three minutes. The temperature and velocity of the wind both affect this. If it be in a dead calm, the time may be considerably extended; if in a considerable wind, it must be shortened. Another important consideration requiring the rapid firing of non-persistent gases is the fact that nearly all masks thoroughly protect against phosgene and similar gases. It is accordingly necessary to take the enemy unawares and gas him before he can adjust his mask; otherwise, practically no harm will result. From the considerations previously mentioned, these “gas shoots” are usually made at night when, as before stated, carelessness, sleepiness and the resulting confusion of battle conditions always insure more casualties than firing gas in the daytime.
Firing Persistent Gases. The persistent gases will be fired by all caliber guns, but to a less extent by the 155 mm. than by the other calibers. Persistent gases must be sufficiently effective in low concentrations to act more or less alone. If it be desirable to fill an atmosphere over a given area with mustard gas, the firing may extend for two or three, or even five or six hours and all shell still act together. The same is true of bromobenzylcyanide. This, then, permits the minimum number of guns to be used in firing these persistent gases. Inasmuch as they persist and force the wearing of the mask, they are available for use in long-range, large-caliber guns for interdiction firing on cross-roads, in villages, and on woods that afford hiding places, as well as on other similar concentration points.
Firing Irritant Gases. The irritant gases will be fired by the various caliber guns, in the same manner as the persistent and non-persistent gases. We will have non-persistent irritant gases and persistent irritant gases. They are, however, considered as a group because they are used for harassing purposes, due to their efficiency in forcing the wearing of the mask.
Before the signing of the Armistice, the General Staff, A. E. F., had authorized, beginning January 1, 1919, the filling of 25 per cent of all shell with Chemical Warfare materials. The interpretation there given to shell was that it included both shrapnel and high explosive.
Of the field guns in use, the 75 mm. will be best, up to the limit of its range, for persistent gases such as mustard gas, and the tear gas, bromobenzylcyanide. A considerable number, however, were filled with non-persistent gases and probably will continue to be so, since, due to the very large number of 75 mm. guns available, they can be used to add greatly at times to the amount of non-persistent gas that can be fired upon a given point.
Use of Gas by the Aviation Service
No gas was used by aeroplanes in the World War. Many rumors were spread during the latter part of the war to the effect that the Germans had dropped gas here or there from aeroplanes. Every such report reaching the Chemical Warfare Service Headquarters was run down and in every case was found to be incorrect. However, there was absolutely no reason for not so using gas, except that the German was afraid. In the early days of the use of gas he did not have enough gas, nor had he developed the use of aeroplanes to the point where it would have seemed advisable. When, however, he had the aeroplanes the war had not only begun to go against him, but he had become particularly fearful of gas and of aeroplane bombing.
It does not seem to be generally known, but it is a fact, that after three or four months’ propaganda he made a direct appeal to the Allies to stop the use of gas sometime during the month of March, 1918. This propaganda took the form of an appeal by a Professor of Chemistry who had access to Switzerland, to prevent the annihilation of the Allied forces by a German gas that was to make its appearance in 1918. This German professor claimed that, while favoring the Germans winning the war, he had too much human sympathy to desire to see the slaughter that would be caused by the use of the new gas. The Allies in the field felt that this was simply an expression of fear and that he did not have such a gas. The Germans were accordingly informed that the Allies would not give up the use of gas. Later events proved these conclusions to be absolutely correct. The German evidently felt that the manufacturing possibilities of the Allies would put them in a more predominant position with gas than with anything else. In that he was exactly correct.