Professor F. P. Kirschbaum, writing on gas warfare, in Schwarte's book, reveals how Germany counted on obtaining the gas initiative against the French at Verdun. He explains how the decision to use Green Cross on a large scale coincided with certain modifications in the design of the German gas shell, which made its large-scale manufacture much simpler and more rapid. "The manufacture of Green Cross," he also tells us, "was assured in the special progress in technical chemistry, and the output was adequate," and goes on to explain, "The first use of per stuff[1] found the enemy unprepared with any suitable protection. The French had equipped their troops with protection against chlorine, but had provided no protection against phosgene,"—"the results of Green Cross ammunition were recognised by the troops. During the big operations before Verdun, however, the enemy did their very utmost to substitute the gas mask M2 for the respirator XTX. Gas mask M2 was a protection against Green Cross. For this reason Green Cross ammunition alone could not be expected to have an effect, as soon as the enemy carried out defensive measures by means of gas mask M2 or some better apparatus. This reverse spurred on the Germans to renewed efforts." The writer proceeds to explain how in 1916 these efforts resulted in finding two important substitutes, mustard gas or Yellow Cross and the arsenic compounds of the Blue Cross type.
[1] Diphosgene or Green Cross constituents.
Yellow and Blue Cross.—The Germans had, somewhat hastily, laid aside their cloud activities. But they were very keenly pursuing another line, the development of shell gas. Thus, in July, 1917, they made two distinct attempts to regain their initiative by the use of shell gas, and were very largely successful in one case. We refer to the Yellow and Blue Cross shell, containing mustard gas and diphenyl-chlorarsine respectively.
Captain Geyer, writing in Schwarte's book, relates: "Gas was used to a much greater extent, over 100,000 shells to a bombardment after the introduction of the Green Cross shell in the summer of 1916 at Verdun. From that time the use of gas became much more varied as the number of types of guns firing gas projectiles was increased, field guns having also been provided with gas projectiles. The most tremendous advance in the use of gas by the artillery, and indeed in the use of gas in general, came in the summer of 1917 with the introduction of the three elements, Green, Yellow, and Blue, one after another. This introduced the most varied possibilities of employing gas, which were utilised to the full in many places on the front during the successful defensive operations of 1917, above all in Flanders and at Verdun. The hardly perceptible poisoning of an area by means of Yellow Cross shell and the surprise gas attack became two of the new regulation methods of using gas."
Yellow Cross.—The respirator afforded complete protection against the attacks of mustard gas on the respiratory system, but this gas evaded protection in other ways. In the first place, its early unfamiliarity evaded the gas discipline of the Allies, and it was not realised in many cases that the respirator was necessary. This was speedily corrected, but its second line of attack was not easily, and never finally countered. We refer to its vesicant action. Mustard gas could produce severe blistering and skin wounds in such slight concentrations, even through clothing, that it was a tremendous casualty producer, putting men out of action for several weeks or months, with a very low rate of mortality. Used in large quantities against an entirely unprotected army, its results might well have been decisive.
This was the first example of chemical attack upon a new function. We had too readily assumed that gas, or chemical attack, would be restricted to the respiratory system, or to the eyes. We had assumed that if our mask protection was ahead of enemy respiratory attacks our situation was safe. Mustard gas was a rude awakening. It was impossible to protect fully against mustard gas, unless we protected the whole body, and it was never possible to do this during the war without too seriously influencing the movements of the soldier.
Blue Cross.—The Blue Cross Shell was a deliberate attempt to pierce the respirator. It represented to the German mind such an advance of aggression over protection that the effect on the enemy would be almost as if he were entirely unprotected. Some idea of the German estimate of its importance can be found in the following quotation from Captain Geyer: "The search for new irritants in the sphere of arsenic combinations led to the discovery of a series of effective substances. In view of the obvious importance of highly irritant compounds capable of existing in a very finely divided, pulverised, or particulate form, research was made in the domain of little volatile substances with boiling points up to 400'0. This led to the astonishing discovery that diphenylarsenious chloride when scattered would penetrate all gas masks then in use, even the German, practically unweakened, and would have serious irritant effects on the wearers. This discovery could only be explained by the supposition that the irritant works in the form of particles which it is difficult to keep back by means of a respirator, even a completely protecting respirator, such as the German and English gas masks were at that time. Further analysis showed that the mixture of air and gas examined revealed a concentration of gas greatly in excess of the point of saturation for the vapour given off by this stuff. Finally, ultra microscopic examination showed the existence of smoke particles. A new type of fighting material had been discovered."
He also tells us how, following this discovery, production rose to 600 tons monthly, and used up all the arsenic obtainable in Germany. The Allies were fully alive to the importance of this matter, and we have already explained that, had they been in possession of large quantities of Blue Cross compounds, they might have forced German protection into an impossible position. No better example could be found of the immense superiority enjoyed by Germany owing to her flexible and efficient producing organisation. Captain Geyer goes on to explain how the military value of these projectiles was considerable, and, therefore, the monthly production reached a figure of over one million shell. We have already emphasised the question of design in chemical warfare, and its importance is borne out by the comparative failure of these German projectiles. Geyer explains how only minute particles less than 1/10,000 of a millimetre in diameter are of any use to penetrate a mask, and he develops the difficulties experienced by Germany in obtaining such fine pulverisation without decomposing the substance. He explains the difficulties which they had in arriving at a suitable shell, and their unsuccessful struggle to overcome the necessity of a glass container, which, he says, demanded "a considerable advance in the technical work of shell production."
This attempt at the chemical initiative by the use of Blue Cross illustrates another method of attack. Geyer says, "Blue and Green Cross ammunition were used simultaneously in the field—called coloured cross (Buntkreuz) in order, by the use of Blue Cross, to force the enemy to remove gas masks, whereby they exposed themselves to the poisonous effects of Green Cross. Matters seldom reached that point, however, for as soon as the enemy realised the effect of `coloured cross' ammunition, they withdrew troops which were being bombarded with it from their positions to a zone beyond the range of artillery fire. The English in particular had tried to protect the troops against the effects of diphenylarsenious chloride, and of diphenylarsenious cyanide (which followed it and was even more effective) by the use of filters made of woollen material and wadding. They were to a great extent technically successful, but the most effective defensive apparatus, the `jacket' to the box, was unsatisfactory from the military point of view, as the troops could only make a limited use of it owing to the difficulty of breathing or suffocation which it occasioned."
The reference to the withdrawal of troops is a picturesque misrepresentation. The relative inefficiency of the German shell rendered this unnecessary. In addition, as Captain Geyer explains, our troops were specially protected in anticipation of the use of particulate clouds. An examination of our protective device by the Germans obviously led them to believe that resistance to breathing was too great for the protective appliance to be practicable. But here the exceptional gas discipline of the British troops became effective. There is no doubt that the new mask was worn just as constantly and satisfactorily as the old. Captain Geyer's remarks are also interesting from a point of view to which we have already referred: they show how much this question of resistance to breathing was exercising the minds of those responsible for German protection.