The moral effect of the constant apprehension that one is being "stalked" is considerable.

Indeed, the combination of our aircraft and our submarine patrols led to our vessels reporting, regretfully, that it was very seldom that German submarines were found on the surface in daylight, and towards the end of 1917 quite a large proportion of the attacks on merchant ships took place at night.
The work for our own vessels was very arduous indeed.

It was only on rare occasions that it was possible to bring off a successful attack on a submarine that had been sighted, the low underwater speed of submarines making it difficult to get into position when the enemy was only sighted at short range, which was naturally usually the case.
In order to obviate this difficulty directions were given in 1917 to design a special type of submarine for this form of warfare, and I believe that the first vessel was completed by the autumn of 1918.
This account of the development of anti-submarine measures during 1917 would not be complete without mention of the work of the Trade Division of the Staff, of which Captain Richard Webb, C.B., was the Director until September.
This Division was either partly or wholly responsible for: (1) The great increase in the rapidity of placing the armaments on board merchant ships.
(2) The establishment of schools of instruction for captains and officers of the Mercantile Marine.
This training scheme was begun at Chatham Barracks in February, 1917, by Commander E.L.B.Lockyer, acting under Captain Webb, and later was extended to Portsmouth, Cardiff and Greenock.

Its success was so marked, and its benefit in assisting officers to handle their ships in the manner best calculated to save them from submarine attack so great, that the Admiralty was continually being pressed by shipowners and by the officers of the Mercantile Marine to extend the instruction to more and more ports.

This was done so far as possible, our principal difficulty being to provide officers capable of giving the instruction required.
(3) The provision of wireless plant and operators to the Mercantile Marine.