It must not be forgotten that the ordinary work of the Dover Patrol could not be interrupted even for one day at this period. The lines of communication across the Channel, important as they had already been throughout the war, were now of such vital importance that the Allied situation on the main battle front depended on the work of the Dover Patrol more than ever before. During February and March, 1918, when the preparations for our enterprise were in full {98} swing, and especially during the latter month, the Germans were concentrating every possible effort to break down the Allied resistance. Their final great "push" was in full swing and the Allied troops were being hard pressed almost to the point of giving way. British, Colonial, and American reënforcements were being poured into France by every available route; guns, ammunition, and stores were passing across the Channel in an endless stream of shipping. The situation was critical to a degree. If the Dover Patrol force had failed at such a time the war might have had a very different ending. And in the midst of this terribly anxious period we were forced to request great additional effort for the purposes which the author is endeavouring to describe. One may be pardoned for thinking that the blocking operation, with all its complicated requirements, should have received undivided attention, but such a thing was impossible. Those were busy days at Dover. Special material, such as artificial fog apparatus, had to be constructed and fitted in the craft concerned. The use of the apparatus had to be practised with a view to discovering the conditions under which the best results could be obtained. Neighbouring commands, such as at Portsmouth and The Nore, were exceedingly helpful in this latter respect. The use of howitzers, flame projectors, bomb-mortars, grappling irons, scaling ladders, and many other fighting appliances not usually found in men-o'-war had to be investigated. [Sidenote: Production of Smoke] A special factory was established at Dover under Wing-Commander Brock--of whom I shall have much to tell--mainly in connection with the {99} developments and use of artificial fog, but also to further the design and production of other material. Sixty men worked at this factory. Their output, both in quality and quantity, was most satisfactory in spite of the many handicaps with which such innovations have to contend. The difficulty of obtaining special material, when the output of every large firm in the country was already earmarked for other purposes, was not lessened by the fact that our urgent demands could seldom be supported, owing to the necessity for secrecy, by explanations as to the purposes in view.