Chemical warfare, besides being the newest, is the most technical and most highly specialized Service under the War Department. There is no class of people in civil life, and no officers or men in the War Department, who can take up chemical warfare successfully until they have received training in its use. This applies not only to the use of materials in attack, but to the use of materials for defense. Ten years from now perhaps this will not be true. It is certainly hoped that it will not be. By that time the entire Army should be pretty thoroughly trained in the general principles and many of the special features of chemical warfare. If not, chemical warfare cannot be used in the field with the efficiency and success with which it deserves to be used. Furthermore, it is believed that within ten years the knowledge of the gases used in chemical warfare will be so common through the development of the use of these same materials in civil life, that it will not be so difficult, as at the present date, to get civilians who are acquainted with Chemical Warfare Service materials. EFFECTIVENESS OF GAS Chemical warfare materials were used during the war by Chemical Warfare Service troops, by the Artillery and by the Infantry. In the future the Air Service and Navy will be added to the above list. Chemical warfare, even under the inelastic methods of the Germans, proved one of the most powerful means of offense with which the American troops had to contend. To realize its effectiveness we need only remember that more than 27 out of every 100 casualties on the field of battle were from gas alone. Unquestionably many of those who died on the battlefield from other causes suffered also from gas. No other single element of war, unless you call powder a basic element, accounted for so many casualties among the American troops. Indeed, it is believed that a greater number of casualties was not inflicted by any other arm of the Service, unless possibly the Infantry, and even in that case it would be necessary to account for all injured by bullets, the bayonet, machine guns and hand grenades. This is true, in spite of the fact that the German was so nearly completely out of gas when the Americans began their offensive at St. Mihiel and the Argonne, that practically no gas casualties occurred during the St. Mihiel offensive, and only a very few until after a week of the Argonne fighting. Furthermore, the Germans knew that an extensive use of mustard gas against the American lines on the day the attack was made, and also on the line that marked the end of the first advance a few days later, would have produced tremendous casualties. Judging from the results achieved at other times by an extensive use of mustard gas, it is believed that had the German possessed this gas and used it as he had used it a few other times, American casualties in the Argonne would have been doubled. In fact, the advance might even have been entirely stopped, thus prolonging the