The warlike character of their ships was even more cleverly hidden. In the early days the guns were placed behind the bulwarks, which, when a lever was pulled, would fall down, thus giving them an unobstructed range at the submarine. In order to make the sides of the ships collapsible, certain seams were unavoidably left in the plates, where the detachable part joined the main structure. The U-boat commanders soon learned to look for these betraying seams before coming to the surface. They would sail submerged around the ship, the periscope minutely examining the sides, much as a scientist examines his specimens with a microscope. This practice made it necessary to conceal the guns more carefully. The places which were most serviceable for this purpose were the hatchways--those huge wells, extending from the deck to the bottom, which are used for loading and unloading cargo. Platforms were erected in these openings, and on these guns were emplaced; a covering of tarpaulin completely hid them; yet a lever, pulled by the gun crews, would cause the sides of the hatchway covers to fall instantaneously. Other guns were placed under lifeboats, which, by a similar mechanism, would fall apart, or rise in the air, exposing the gun. Perhaps the most deceptive device of all was a gun placed upon the stern, and, with its crew, constantly exposed to public gaze. Since most merchantmen carried such a gun, its absence on a mystery ship would in itself have caused suspicion; this armament not only helped the disguise, but served a useful purpose in luring the submarine. At the first glimpse of a U-boat on the surface, usually several miles away, the gun crew would begin shooting; but they always took care that the shots fell short, thus convincing the submarine that it had the advantage of range and so inducing it to close.
Captain Campbell and his associates paid as much attention to details in their ships as in their personal appearance. The ship's wash did not expose the flannels that are affected by naval men but the dungarees that are popular with merchant sailors. Sometimes a side of beef would be hung out in plain view; this not only kept up the fiction that the ship was an innocent tramp, but it served as a tempting bait to the not too well-fed crew of the submarine. Particularly tempting cargoes were occasionally put on deck. One of the ships carried several papier-mâché freight cars of the small European type covered with legends which indicated that they were loaded with ammunition and bound for Mesopotamia. It is easy to imagine how eagerly the Hun would wish to sink that cargo!