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pressure on manufacturers, it was not until November, 1917, that mines
of this pattern were being delivered in large numbers. The earliest
minefields laid in the Heligoland Bight in September and October, 1917,
with mines of the new pattern met with immediate success against enemy
submarines, as did the minefields composed of the same type of mine, the
laying of which commenced in November, 1917, in the Straits of Dover.

When it became possible to adopt the system of bringing merchant ships
in convoys through the submarine zone under the escort of a screen of
destroyers, this system became in itself, to a certain extent, an
offensive operation, since it necessarily forced the enemy submarines
desirous of obtaining results into positions in which they themselves
were open to violent attack by depth charges dropped by destroyers.

During the greater part of the year 1917, however, it was only possible
to supply destroyers with a small number of _depth charges_, which was
their principal anti-submarine weapon; as it became feasible to increase
largely the supply of these charges to destroyers, so the violence of
the attack on the submarines increased, and their losses became heavier.

The position then, as it existed in the early days of the year 1917, is
described in the foregoing remarks.

The _result_ measured in loss of shipping (British, Allied, and neutral)
from submarine and mine attack in the first half of the year was as
follows in gross tonnage:

January - 324,016
February - 500,573
March - 555,991
April - 870,359
May - 589,754
June - 675,154

Because of the time required for production, it was a sheer
impossibility to _put into effect_ any fresh devices that might be
adopted for dealing with submarine warfare for many months, and all that
could be done was to try new methods of approach to the coast and, as
the number of small craft suitable for escort duty increased, to extend
gradually the convoy system already in force to a certain extent for the
French coal trade and the Scandinavian trade.

In the chapters which follow the further steps which were taken to deal
with the problem, and the degree of success which attended them, will be
described.


CHAPTER III

ANTI-SUBMARINE OPERATIONS


The previous chapters have dealt with the changes in organization
carried out at the Admiralty during the year 1917 largely with the
object of being able to deal more effectively with the submarine warfare
against merchant ships. Mention has also been made of the submarine
problem with which the Navy had to deal; particulars of the
anti-submarine and other work carried out will now be examined.

A very large proportion of the successful anti-submarine devices brought
into use during 1917, and continued throughout the year 1918, were the
outcome of the work of the Anti-Submarine Division of the Naval Staff,
and it is but just that the high value of this work should be recognized
when the history of the war comes to be written by future historians. As
has been stated in Chapter I, Rear-Admiral A.C. Duff, C.B., was the
original head of the division, with Captain F.C. Dreyer, C.B., Commander
Yeats Brown, and Commander Reginald Henderson as his immediate
assistants. Captain H.T. Walwyn took the place of Captain Dreyer on
March 1, 1917, when the latter officer became Director of Naval
Ordnance. When Admiral Duff was appointed Assistant Chief of the Naval
Staff, with a seat on the Board, in May, 1917, Captain W.W. Fisher,
C.B., became head of the division, which still remained one of the
divisions of the Staff working immediately under the A.C.N.S. It is to
these officers, with their most zealous, clever and efficient staff,
that the institution of many of the successful anti-submarine measures
is largely due. They were indefatigable in their search for new methods
and in working out and perfecting fresh schemes, and they kept their
minds open to _new ideas_. They received much valuable assistance from
the great civilian scientists who gave such ready help during the war,
the function of the naval officers working with the scientists being to
see that the effort was being directed along practical lines. They were
also greatly indebted to Captain Ryan, R.N., for the exceedingly
valuable work carried out by him at the experimental establishment at
Hawkcraig. Many brilliant ideas were due to Captain Ryan's clever brain.

I doubt whether the debt due to Admiral Duff and Captain Fisher and
their staff for their great work can ever be thoroughly appreciated, but
it is certainly my duty to mention it here since I am better able to
speak of it than any other person. In saying this I do not wish to
detract in the least from the value of the part performed by those to
whose lot it fell to put the actual schemes into operation. Without
them, of course, nothing could have been accomplished.

When the Anti-Submarine Division started in December, 1916, the earlier
devices to which attention was devoted were:

(1) The design and manufacture of howitzers firing shell fitted to
explode some 40 to 60 feet under water with which to attack submarines
when submerged.

(2) The introduction of a more suitable projectile for use against
submarines than that supplied at the time to the guns of destroyers and
patrol craft.

(3) The improvement of and great increase in the supply of smoke
apparatus for the screening of merchant ships from submarines attacking
by gunfire.

(4) A great increase in the number of depth charges supplied to
destroyers and other small craft.

(5) The development of the hydrophone for anti-submarine work, both from
ships and from shore stations.

(6) The introduction of the "Otter" for the protection of merchant ships
against mines.

(7) A very great improvement in the rapidity of arming merchant ships
defensively.

(8) The extended and organized use of air craft for anti-submarine work.

(9) A great development of the special service or decoy ship.

(10) The introduction of a form of net protection for merchant ships
against torpedo fire.

Other devices followed, many of which were the outcome of work in other
Admiralty Departments, particularly the Departments of the Director of
Naval Ordnance and the Director of Torpedoes and Mines, working in
conjunction with the Anti-Submarine or the Operations Division of the
Naval Staff. Some of the new features were the development of
depth-charge throwers, the manufacture and use of fast coastal
motor-boats for anti-submarine work, the production of mines of an
improved type for use especially against submarines, very considerable
developments in the use of minefields, especially deep minefields,
including persistent mining in the Heligoland Bight and the laying of a
complete minefield at varying depths in the Straits of Dover; also,
after the United States entered the war, the laying of a very extensive
minefield right across the northern part of the North Sea. The provision
of "flares" for illuminating minefields at night, and a system of
submarine detection by the use of electrical apparatus were also matters
which were taken up and pressed forward during 1917. During the year the
system of dazzle painting for merchant ships was brought into general
use.

On the operational side of the Naval Staff the work of dealing with
enemy submarines before they passed out of the North Sea was taken in
hand by organized hunting operations by destroyers and other patrol
craft, and by the more extended use offensively of our own submarines,
as vessels became available.

Considerable developments were effected in the matter of the control of
mercantile traffic, and much was done to train the personnel of the
mercantile marine in matters relating to submarine warfare.

Taking these subjects in detail, it will be of interest to examine the
progress made during the year.


HOWITZERS

The _howitzer_ as a weapon for use against the submarine when submerged
was almost non-existent at the beginning of 1917, only thirty
bomb-throwers, on the lines of trench-mortars, being on order. By April
of that year designs for seven different kinds of bomb-throwers and
howitzers had been prepared and approved, and orders placed for 1,006
weapons, of which number the first 41 were due for delivery in May. By
the end of May the number of bomb-throwers and howitzers on order had
been increased to 2,056, of eight different patterns. Over 1,000 of
these weapons fired a bomb or shell carrying a burster exceeding 90 lbs.
in weight, and with a range varying between 1,200 and 2,600 yards. Later
in the war, as we gained experience of the value of this form of attack,
heavier bombs were introduced for use in the existing bomb-throwers and
howitzers. The howitzer as an anti-submarine weapon was handicapped by
the comparatively small weight of the bursting charge of its shell. This
applied more particularly to the earlier patterns, and to inflict fatal
injury it was necessary to burst the shell in close proximity to the
submerged submarine. This weapon, although not very popular at first,
soon, however, proved its value, when employed both from patrol craft
and from merchant ships.

One curious instance occurred on March 28, 1918, of a merchant ship
being saved by a 7.5-inch howitzer. A torpedo was seen approaching at a
distance of some 600 yards, and it appeared certain to hit the ship. A
projectile fired from the howitzer exploded under water close to the
torpedo, deflected it from its course, and caused it to come to the
surface some 60 yards from the ship; a second projectile caused it to
stop, and apparently damaged the torpedo, which when picked up by an
escorting vessel was found to be minus its head.

Delivery of howitzers commenced in June, 1917, and continued as follows:

Total completed,
No. of Howitzers including those
Date. actually issued. under proof.

July 24, 1917 35 48
October 1, 1917 92 167
December 10, 1917 377 422

The slow rate of delivery, in spite of constant pressure, which is shown
by these figures gives some idea of the time required to bring new
devices into existence.


PROJECTILE FOR USE AGAINST SUBMARINES

In January, 1917, the Director of Naval Ordnance was requested by the
Anti-Submarine Division of the Naval Staff to carry out trials against a
target representing the hull of a German submarine, so far as the
details were known to us, to ascertain _the most suitable type of
projectile_ amongst those then in existence for the attack of submarines
by guns of 4.7-inch calibre and below.

The results were published to the Fleet in March, 1917. They afforded
some useful knowledge and demonstrated the ineffectiveness of some of
the shells and fuses commonly in use against submarines from 12-pounder
guns, the weapon with which so many of our patrol craft were armed. The
target at which the shell was fired did not, however, fully represent a
German submarine under the conditions of service. The trials were
therefore continued, and as a result, in June, 1917, a further order was
issued to the Fleet, giving directions as to the type of projectile to
be used against submarines from all natures of guns, pending the
introduction of delay action fuses for the smaller guns; this was the
temporary solution of the difficulty until a new type of shell evolved
from the experience gained at the trials could be produced and issued.
The trials, which were exhaustive, were pressed forward vigorously and
continuously throughout the year 1917, and meanwhile more accurate
information as to the exact form of the hull and the thickness of the
plating of German submarines became available. Early in 1918 the first
supplies of the new fuses were ready for issue.


SMOKE APPARATUS

The earlier _smoke apparatus_ for supply to merchant ships was designed
towards the end of 1916.

One description of smoke apparatus consisted of an arrangement for
burning phosphorus at the stern of a ship; in other cases firework
composition and other chemicals were used. A dense smoke cloud was thus
formed, and, with the wind in a suitable direction, a vessel could hide
her movements from an enemy submarine or other vessel, and thus screen
herself from accurate shell fire.

In another form the apparatus was thrown overboard and formed a smoke
cloud on the water.

The rate of supply of sets of the smoke apparatus to ships is shown by
the following figures:

April 1, 1917 - 1,372 sets
July 3, 1917 - 2,563 sets
October 5, 1917 - 3,445 sets
November 26, 1917 - 3,976 sets


DEPTH CHARGES

_Depth charges_, as supplied to ships in 1917, were of two patterns:
one, Type D, contained a charge of 300 lb. of T.N.T., and the other,
Type D*, carried 120 lb. of T.N.T. At the commencement of 1917 the
allowance to ships was two of Type D and two of Type D*, and the supply
was insufficient at that time to keep up the stock required to maintain
on board four per destroyer, the number for which they were fitted, or
to supply all trawlers and other patrol craft with their allowance. The
great value of the depth charge as a weapon against submarines, and the
large number that were required for successful attack, became apparent
early in 1917, and the allowance was increased. Difficulty was
experienced throughout the year in maintaining adequate stocks owing to
the shortage of labour and the many demands on our industries made by
the war, but the improvement is shown by the fact that while the average
output _per week_ of depth charges was only 140 in July, it had become
over 500 by October, and that by the end of December it was raised to
over 800, and was still increasing very rapidly. As a consequence, early
in 1918 it was found possible to increase the supply very largely, as
many as 30 to 40 per destroyer being carried.

Improvements in the details of depth charges were effected during 1917.
One such improvement was the introduction of a pistol capable of firing
at much greater depths than had been in use before. The result was that
all vessels, whether fast or slow, could safely use the 300-lb. depth
charge if set to a sufficient depth. This led to the abolition of the
Type D* charges and the universal supply of Type D.

In spite of the difficulties of dropping depth charges so close to
submarines as to damage them sufficiently to cause them to come to the
surface, very good results were obtained from their use when destroyers
carried enough to form, so to speak, a ring round the assumed position
at which the submarine had dived. In order to encourage scientific
attack on submarines, a system of depth charge "Battle Practice" was
introduced towards the end of 1917.

It is as well to correct a common misapprehension as to the value of
depth charges in destroying submarines.

Many people held very exaggerated ideas on this subject, even to the
extent of supposing that a depth charge would destroy a submarine if
dropped within several hundred yards of her. This is, unfortunately,
very far indeed from being the case; it is, on the contrary, necessary
to explode the charge near the submarine in order to effect destruction.
Taking the depth charge with 300 lb. weight of explosive, ordinarily
supplied to destroyers in 1917, it was necessary to explode it within
fourteen feet of a submarine to ensure destruction; at distances up to
about twenty-eight feet from the hull the depth charge might be expected
to disable a submarine to the extent of forcing her to the surface, when
she could be sunk by gun-fire or rammed, and at distances up to sixty
feet the moral effect on the crew would be considerable and _might_
force the submarine to the surface.

A consideration of these figures will show that it was necessary for a
vessel attacking a submarine with depth charges to drop them in very
close proximity, and the first obvious difficulty was to ascertain the
position of a submarine that had dived and was out of sight.

Unless, therefore, the attacking vessel was fairly close to the
submarine at the moment of the latter diving there was but little chance
of the attack being successful.


HYDROPHONES

The _Hydrophone_, for use in locating submerged submarines, although
first evolved in 1915, was in its infancy, so far as supply to ships was
concerned, at the commencement of 1917. Experiments were being carried
out by the Board of Invention and Research at Harwich, and by Captain
Ryan, R.N., at Hawkcraig, and although very useful results had been
obtained and a considerable number of shore stations as well as some
patrol vessels had been fitted with hydrophones, which had a listening
range of one or two miles, all the devices for use afloat suffered from
the disadvantage that it was not possible to use them whilst the ship
carrying them was moving, since the noise of the vessel's own machinery
and of the water passing along the side prevented the noise made by
other vessels being located. What was required was a listening
instrument that could be used by a ship moving at least at slow speed,
otherwise the ship carrying the hydrophone was herself, when stopped, an
easy target for the submarine's torpedo. It was also essential, before
an attack could be delivered, to be able to locate the _direction_ of
the enemy submarine, and prior to 1917 all that these instruments showed
was the presence of a submarine somewhere in the vicinity.

Much research and experimental work was carried out during the year 1917
under the encouragement and supervision of the Anti-Submarine Division
of the Naval Staff. Two hydrophones were invented in the early part of
1917, one by Captain Ryan, R.N., and one by the Board of Invention and
Research, which could be used from ships at very slow speed and which
gave some indication of the _direction_ of the sound; finally, in the
summer of 1917, the ability and patience of one inventor, Mr. Nash, were
rewarded, and an instrument was devised termed the "fish" hydrophone
which to a considerable extent fulfilled the required conditions. Mr.
Nash, whose invention had been considered but not adopted by the Board
of Invention and Research before he brought it to the Anti-Submarine
Division of the Naval Staff, laboured under many difficulties with the
greatest energy and perseverance; various modifications in the design
were effected until, in October, 1917, the instrument was pronounced
satisfactory and supplies were put in hand.

The next step was to fit the "fish" hydrophone in certain auxiliary
patrol vessels as well as some destroyers, "P" boats and motor launches,
to enter and train men to work it, and finally to organize these vessels
into "submarine hunting flotillas," drill them, and then set them to
their task.

This work, which occupied some time, was carried out at Portland, where
a regular establishment was set up for developing the "fish" hydrophone
and for organizing and training the "hunting flotillas" in its use. A
considerable amount of training in the use of the hydrophone was
required before men became efficient, and only those with a very keen
sense of hearing were suited to the work. The chances of the success of
the hunting flotillas had been promising in the early experiments, and
the fitting out of patrol craft and organizing and drilling them,
proceeded as rapidly as the vessels could be obtained, but largely owing
to the slow production of trawlers it was not until November that the
first hunting flotilla fitted with the "fish" hydrophone was actually at
work. The progress made after this date is illustrated by the fact that
in December, 1917, a division of drifters, with a "P" boat, fitted with
this "fish" hydrophone hunted an enemy submarine for seven hours during
darkness, covering a distance of fifty miles, kept touch with her by
sound throughout this period, and finished by dropping depth charges in
apparently the correct position, since a strong smell of oil fuel
resulted and nothing further could be heard of the submarine, although
the drifters listened for several hours. On another occasion in the same
month a division of drifters hunted a submarine for five hours. The
number of hydrophones was increased as rapidly as possible until by the
end of the year the system was in full operation within a limited area,
and only required expansion to work, as was intended, on a large scale
in the North Sea and the English Channel.

Meanwhile during 1917 _directional_ hydrophones, which had been
successfully produced both by Captain Ryan and by the Board of Invention
and Research, had been fitted to patrol craft in large numbers, and
"hunting flotillas" were operating in many areas. A good example of the
working of one of these flotillas occurred off Dartmouth in the summer
of 1918, when a division of motor launches fitted with the Mark II
hydrophone, under the general guidance of a destroyer, carried out a
successful attack on a German submarine. Early in the afternoon one of
the motor launches dropped a depth charge on an oil patch, and shortly
afterwards one of the hydrophones picked up the sound of an internal
combustion engine; a line of depth charges was run on the bearing
indicated by the hydrophone. The motor launches and the destroyer
remained listening, until at about 6.0 P.M. a submarine came to the
surface not far from Motor Launch No. 135, which fired two rounds at the
submarine before the latter submerged. Other motor launches closed in,
and depth charges were dropped by them in close proximity to the wash of
the submarine. Oil came to the surface, and more depth charges were
dropped in large numbers on the spot for the ensuing forty-eight hours.
Eventually objects came to the surface clearly indicating the presence
of a submarine. Further charges were dropped, and an obstruction on the
bottom was located by means of a sweep. This engagement held peculiar
interest for me, since during my visit to Canada in the winter of 1919
the honour fell to me of presenting to a Canadian - Lieutenant G.L.
Cassady, R.N.V.R. - at Vancouver the Distinguished Service Cross awarded
him by His Majesty for his work in Motor Launch No. 135 on this
occasion.

_Motor Launches_ were organized into submarine hunting flotillas during
the year 1917. These vessels were equipped with the directional
hydrophone as soon as its utility was established, and were supplied
with depth charges. In the summer of 1917 four such hunting flotillas
were busy in the Channel; the work of one of these I have described
already, and they certainly contributed towards making the Channel an
uneasy place for submarine operations.

These results were, of course, greatly improved on in 1918, as the
numbers of ships fitted with the "fish" and other hydrophones increased
and further experience was gained.

The progress in supply of hydrophones is shown by the following table:

Supply of Directional
Date General Service Mark I and Shark Fin Fish
1917. Portable Type. Mark II. Type. Type.

Jul 31 2,750 500 - -
Aug 31 2,750 700 - -
Sep 30 2,750 850 - -
Oct 31 3,500 1,000 - -
Dec 31 3,680 1,950 870 37


HYDROPHONE STATIONS AND TRAINING SCHOOLS

At the beginning of 1917 four _shore hydrophone stations_ were in use.
During the year eight additional stations were completed and several
more were nearing completion. The first step necessary was a
considerable increase in the instructional facilities for training
listeners both for the increased number of shore stations and for the
large number of vessels that were fitted for hydrophone work during the
year.

The greater part of this training took place at the establishment at
Hawkcraig, near Rosyth, at which Captain Ryan, R.N., carried out so much
exceedingly valuable work during the war. I am not able to give exact
figures of the number of officers and men who were instructed in
hydrophone work either at Hawkcraig or at other stations by instructors
sent from Hawkcraig, but the total was certainly upwards of 1,000
officers and 2,000 men. In addition to this extensive instructional work
the development of the whole system of detecting the presence of
submarines by sound is very largely due to the work originally carried
out at Hawkcraig by Captain Ryan.


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