Long before the chemical plants were completed it became evident that civilian labor could not be utilized in their operation. Not only was such labor difficult to obtain, but the wages were abnormally high, the work was, as a whole, extremely inefficient, and it was virtually impossible to maintain the discipline and secrecy imperative to the success of the undertaking. Moreover, it was found that such civilian labor as was available could not be depended upon to work in the chemical plants because of the danger attending the manufacture of such highly poisonous materials. It was decided, therefore, to utilize enlisted men. As the project progressed, increasing numbers of soldiers from the National Army were detailed to the arsenal, the force reaching a strength of 7,400 at one time. The soldiers, no matter how much they disliked the work, could not quit like the civilian laborers; they had no option but to obey orders, and so, morning after morning, they rose at the summons of the bugles in the dim light of early dawn, hurried through their breakfasts at the long tables in the mess-halls, and marched to their respective tasks, whether making chlorine, chlorpicrin, phosgene, or mustard gas, filling or painting shell, working in the great refrigerating-plants through which the shell were passed to be chilled before filling, loading trains and boats, building roads, digging ditches, or firing boilers—all for thirty dollars a month. To the men who wore the blue-and-yellow hat-cords of the Chemical Warfare Service, the men who performed their dangerous work without advertisement and without public recognition, is due the gratitude of the nation. The chief activities of the great arsenal on the Chesapeake consisted, as I believe I have already mentioned, of the manufacture of four types of toxic-gas—chlorine, chlorpicrin, phosgene, and mustard—and the filling of shell with these gases. Now I have not the slightest intention of entering upon a technical account of the complicated processes by which these gases were produced. Though no doubt interesting to chemists, it would make dry reading for others. It will suffice for the purposes of this book to sketch in briefest outline, and in simple words, the chief characteristics of the principal toxic-gases and the methods followed in their manufacture.