This chapter should not be closed without reference to the Liaison Service that was established between the United States and her Allies, especially England. During the early days no one in the States was familiar with the details of gas warfare. At the request of the Medical Corps, upon the urgent representations of the Gas Service, A.E.F., Captain (now Major) H. W. Dudley was sent to this country (Sept., 1917) to assist in the development and manufacture of gas masks. For some time he was the Court of Appeal on nearly all technical points regarding matters of defense. Dudley’s continual insistence on the need for maintaining the highest possible standard of factory inspection was one of the factors resulting in the excellent construction of the American Mask. In March, 1918, Lieut. Col. Dewey and Captain Dudley made a trip to England and France, during which the idea of a liaison between the defense organizations of the two countries originated. Dudley was transferred to the Engineers, promoted and placed in charge of the Liaison service. While the time until the Armistice was too short to really test the idea, enough was accomplished to show the extreme desirability of some such arrangement. Probably the best known liaison officer from the British was Colonel S. J. M. Auld, also sent upon the urgent representations of the Gas Service, A.E.F. He arrived in this country about the middle of October, 1917, in charge of 28 officers and 28 non-commissioned officers, who were to act as advisers in training and many other military subjects besides gas warfare. Since Auld had had personal experience with gas warfare as then practiced at the front, his advice was welcomed most heartily by all the different branches of the Army then handling gas warfare. On questions of general policy Auld was practically the sole foreign adviser. The matter of gas training was transferred from the Medical Corps to the Engineers, and was greatly assisted by four pamphlets on Gas Warfare issued by the War College, which were prepared by Major Auld with the assistance of Captain Walton and Lieut. Bohnson. Later Auld gave the American public a very clear idea of gas warfare in his series of articles appearing in the Saturday Evening Post, and re-written as “Gas and Flame.” Major H. R. LeSueur, who was at Porton previous to his arrival in this country in December, 1917, rendered valuable aid in establishing the Experimental Proving Ground and in its later operations. Towards the close of the war the British War Office had drawn up a scheme for a Gas Mission, which was to correlate all the gas activities of England and America. This was never carried through because of the signing of the Armistice. The French representatives, M. Grignard, Capt. Hanker and Lt. Engel furnished valuable information as to French methods, but they were handicapped by the fact that French manufacturers did not disclose their trade secrets even to their own Government.