Evidence is found in the introduction of the German three-layer drum in the autumn of 1916. An army does not undertake the manufacture of millions of new appliances without very good reason. This new drum was specially aimed at phosgene protection. The middle layer consisted of granulated absorbent charcoal, which had the property of absorbing large quantities of organic irritants and phosgene. In the three-layer drum the latter gas was adequately guarded against for most field purposes, although we have reason to believe that the German staff was always apprehensive, and German soldiers suspicious of the actual penetration of their mask obtained in the immediate locality of projector discharges.
Dr. Pick explains in Schwarte's book what is already well known, that the charcoal layer has a wide, "non-specific effect, and it retains almost all materials of which the molecular weight is not too small, even if very strongly neutral in character (as, for example, chlorpicrin)." He goes on to say "the progressive development of gas warfare led to the use of these very materials, whilst substances with acid properties, such as chlorine, fell more and more into disuse. The three-layer drum went through all sorts of changes in consequence. When the use of chlorpicrin mixtures gained in importance in 1917, the layer of charcoal was increased at the expense of the other two layers. This stage of development ended in 1918, when the other layers were done away with altogether, and the entire three sets were filled with `A' charcoal." " `A' charcoal was a particularly efficient form. We learn from the same source that the increased protection against phosgene was very welcome to the Germans in view of the danger arising from gas projector attacks. Further, the capacity for absorption of the German charcoal was never equalled by any of foreign production." This was certainly true for the greater part of the war. But Dr. Pick continues, in a sentence which is full of significance: "In consequence of the high quality of the drum's absorption, we were able to carry on to the end of the war with a drum of relatively small proportions." This point is so important as to demand further explanation.
Enforced German Modifications.—The most important disadvantage of a gas mask is its resistance to breathing. Men undertaking arduous and dangerous duties in the presence of gas must wear a mask, but they cannot undertake these duties if their breathing is seriously interfered with. This is particularly so in trench engineering and in the heavy work of the artillery. Now the resistance depends, for a given type of filling, upon the area of the cross-section of the drum. Breathing will be easier through a very large area than through a very small one. The British appliance was a frank admission that, with its filling, a large drum was necessary, so large that the weight of it could not be borne by the mask itself, but by attachment to the chest, the actual mask being connected with the drum or box by a flexible rubber tube. But the Germans adopted from the beginning a form of protective appliance in which the drum or cartridge was attached to and supported by the mask. In other words, their development was limited by the weight of their drum, unless they completely changed their type on British lines. It is quite clear that they realised this, for Doctor Pick tells us, referring to the large size of the British box: "For this reason the weight of the box is so great that it is no longer possible to attach it directly to the mask. It is, therefore, carried on the chest and joined to the mouthpiece of the mask by a flexible tube."
The development of British cloud gas compelled the Germans so to modify their filling that the resistance to breathing increased considerably. They countered this, however, by introducing an exceedingly active charcoal, realising that the weight of their drum had already reached the limit possible with that type of apparatus, and that they could not, therefore, get better breathing capacity by increasing its size. When, however, the Blue Cross compounds were introduced, it was necessary for both armies to take special precautions. These precautions involved introducing a layer of filtering material into the canister or drum. Dr. Pick tells us: "When the material of the Blue Cross type became of greater importance, a supplementary apparatus had to be issued. A thin disc filter prepared by a special method from threads of cotton was fastened to the tube of the drum by means of a spring lid. This arrangement provided adequate protection against materials of the Blue Cross type used by the enemy, as, for instance, stannic chloride, whilst the German Blue Cross gas, which was more penetrating, was only retained to a moderate degree." This is a direct admission that, in order to counter the Allied use of Blue Cross gas, further filtering arrangements would have been necessary. But the resistance to breathing of the German apparatus was already strained to the utmost. It is exceedingly improbable that the Germans, having already reached the limit of size of the canister or drum, and being unable to obtain better breathing by increase in size, could have introduced any such device without carrying their resistance beyond the possible limit. In other words, the use of Blue Cross by the Allies would have compelled them to adopt the British type of apparatus, that is, a bigger box supported by the chest and connected to the mask by a flexible rubber tube. This would have led them into an impasse.
Shortage of Rubber.—We know how, in the beginning of 1917, they were compelled to substitute leather in the substance of the mask. Dr. Pick admits that this was due to lack of raw material, rubber, and there are many other signs that this was so. Although leather was not altogether a bad substitute for this purpose, rubber would have been essential for the flexible tube, and the millions required to refit the army would have completely broken the German rubber resources. Many facts, including their feverish development of synthetic rubber, small quantities of which they obtained at enormous cost, go to prove this conclusion. The submarine, Deutschland, returning to Germany in 1916, from its historic trip to America, carried shipments of the most sorely needed commodities, including large quantities of raw rubber. Stringent measures were adopted later to collect waste rubber and prevent its use for such purposes as billiard tables and tyres for private vehicles. The first naval expedition to Baltic ports after the Armistice found the hospitals in a pitiable plight for lack of rubber. The Germans were being driven into an impossible position. In other words, the Allies, by a proper use of Blue Cross compounds, could have regained the gas initiative. There is no doubt that they were within a few months of doing so. Once again we see the importance of production. Lack of raw materials for protective purposes was endangering the German position, but delay in offensive production by the Allies removed that danger. Although their pressing need was obvious, the Blue Cross arsenic compounds were not available. The chemical war involves manoeuvring for position just as definitely as the older forms, but in it production, formerly a routine activity, assumes critical strategic importance.
Gas Discipline.—This constant vigilance against enemy surprise imposed more conditions upon the troops than the permanent adoption of a protective appliance which, in itself, was a very big thing. Given the mask, the army had to be taught how and when to use it. A gas sense had to be developed which ensured rapid use of the mask at the right time with the least hampering of operations. Gas discipline thus became one of the most important features of general training, a feature which can never be abandoned by the armies of civilised nations in the future without disastrous results. This discipline, like all other protective work, was dependent in its nature and intensity upon the struggle for the initiative. One example out of many is found in the numerous German Army Orders which followed our introduction of the Livens projector. This weapon gave the possibility of much higher concentrations at much greater ranges from the front line than were formerly possible and for a time German gas discipline was severely shaken, and the staffs had to react violently to meet the situation. The introduction of this weapon, in fact, was the first clear case of the gaining of the chemical initiative by the Allies. A telegram from German General Headquarters stated: "The English have achieved considerable success by firing gas mines simultaneously from a considerable number of projectors on to one point. Casualties occurred because the gas was fired without warning, and because its concentration was so great that a single breath would incapacitate a man."
This is a further example of the fact that the decisive initiative was very difficult to obtain after two years of war, whereas by the same means it would have been ensured at the commencement. The general development of German protection was a partial safeguard, but the value of the weapon could be seen from the fact that an order was issued for all German working parties to wear gas masks when within 1000 yards of the front line on nights not obviously unsuitable for Allied gas discharges. It is difficult to exaggerate the military importance of such an imposition.
Summary.—We have thus covered a period, the main features of which were attempts at the cloud initiative by Germany and our rapid and successful protective reaction. The conditions surrounding the first attack were entirely peculiar. The complete surprise attending it could only be repeated at the commencement of another war. It failed for entirely different reasons from those which prevented the decisive use of phosgene by the Germans. But our reaction carried us further, and we developed the final form of cloud gas attack, the Livens projector, which, in its turn, taxed the German protection to the utmost, and threatened to overcome it. History repeated itself with a vengeance in this protective struggle.
Two attempts at the cloud initiative, the German phosgene attempt and the Livens projector, were both partially successful. Had either of those attempts shared the surprise of April 22nd, 1915, their success would have been many times greater. It was contact on the battle front that developed a protective appliance and organisation, by giving us an insight into enemy appliances and projects. We cannot emphasise too strongly the significance of this for the future. Apart from remote exceptions, contact will be entirely absent. We can have no guarantee whatever that new devices will be revealed, either between nations or to a central body. Suppose the Germans had been more fully aware of the possibilities of cloud gas, and, realising the dependence of their one method upon wind direction and caprice, had developed our method of producing cloud at a distance. The combinations of the two methods at Ypres could hardly have left a margin of chance for failure. This is a feeble example of what may occur.
New German Attempts.—By this time it was not easy to see how either side could obtain a decisive surprise by the use of chemicals aimed at the respiratory system. It appeared very difficult to penetrate the different forms of respirators by conditions obtainable in the field.