ey
would be almost immune from torpedo attack.

A very good design was produced, and some of the later patrol boats were
converted and called "P Q's." These vessels had the appearance of small
merchant ships at a cursory glance. They would not, however, stand close
examination owing, again, to their fine lines, but being better sea
boats than the "P's," by reason of their greater freeboard, the design
was continued, and they met with considerable success against submarines
(especially in the Irish Sea) by ramming and depth charge tactics, the
submarines when submerged probably not realizing when observing the "P
Q.'s" through a periscope the speed of which they were capable.

During 1917, when the unrestricted submarine warfare was in progress,
many of the decoy vessels were fitted with torpedo tubes, either above
water or submerged, since, as the submarine commanders became more wary,
they showed great dislike to coming to the surface sufficiently close to
merchant ships to admit of the gun armament being used with certainty of
success. A torpedo, on the other hand, could, of course, be used
effectively against a submarine whilst still submerged. The use also
became general of casks or cargoes of wood to give additional flotation
to decoy ships after being torpedoed, so as to prolong their life in
case the submarine should close near enough to allow of effective
gunfire.

Another ruse adopted was that of changing the disguise of a decoy ship
during the night, so that she could not be identified by a submarine
which had previously made an attack upon her. In all cases of disguise
or of changing disguise it was essential that the decoy ship should
assume the identity of some class of vessel likely to be met with in the
particular area in which she was working, and obviously the courses
steered were chosen with that object in view.

Again, since for success it was essential to induce the submarine to
come within close range so that the decoy ship's gunfire should be
immediately effective, it was necessary that her disguise should stand
the closest possible examination through the periscope of a submarine.
German submarine commanders, after a short experience of decoy ships,
were most careful not to bring their vessels to the surface in proximity
to craft that were apparently merchant ships until they had subjected
them to the sharpest scrutiny at short range through the periscope, and
the usual practice of an experien