SUBMARINES IN ACTION
Submarines have two great advantages over all types of surface warships;
they can become invisible at will—or sufficiently invisible to make gun
or torpedo-practice, except at very close quarters, almost entirely
useless—and they can, by sinking, cover themselves with armour-plate of
sufficient thickness to be absolutely shell-proof. These are the two
main points in favour of the submarine. There are, however, many minor
features. Although submarines are known in the naval services as
“daylight torpedo-boats,” for their _greatest_ value lies in their
ability to perform the same task in the “light” as the ordinary surface
torpedo-boats and destroyers can do under cover of darkness or fog—that
of creeping up close to an enemy, and launching a torpedo
unobserved—they have been given, during recent years, so much greater
speed, armament, and range of action, that they can no longer be looked
upon as small boats just suitable for daylight torpedo attack in
favourable circumstances. Their surface speed has been increased from 10
to 20 knots, making them almost as fast as the surface torpedo-boat.
This, combined with manœuvering powers and general above-water
invisibility, has enabled them to take over the duty of the surface
torpedo-boat—that of delivering night-attacks on the surface. After
nightfall a submarine attack is almost impossible owing to the
periscope—the eyes of the submarine—being useless in the dark.
The increase in the armament of the submarine—from the single bow
torpedo tube with two torpedoes of short range and weak explosive
charge, to the four bow and two stern tubes with eight or ten torpedoes
of long range and high explosive charge—has greatly increased their
chances of successful attack on surface warships, first, by giving them
four or six shots ahead, then the possibility, in the event of all these
torpedoes missing, of a dive under the object of attack, and two more
shots at close range from the stern tubes (still retaining two
torpedoes); and, secondly, by increasing the distance from which the
first projectile can be launched, owing to the increased range of the
modern torpedo. There are also the advantages derived from the battery
of quick-firing guns installed on the decks of modern submarines.
Although at the present time these guns are only of small power they
nevertheless afford a means of defence—and even of attack under
favourable circumstances—against hostile surface torpedo-boats,
destroyers, and air-craft. In fact, a flotilla of submarines could
undoubtedly now give a very good account of itself if attacked either on
the surface or when submerged by one or two prowling destroyers. The
increase in the power of the guns carried by submarines, which will
certainly come soon, will enable this type of craft to take up the
additional duties of the destroyer—that of clearing the seas of hostile
torpedo-boats and carrying out advanced scouting—for which work their
ability to travel submerged and in a state of invisibility for distances
of over 100 miles makes them eminently suitable.
The enormous increase in the size and range of action of submarines,
combined with the improvements effected in the surface cruising
qualities, have enabled these vessels to be taken from the “nursery” of
harbour and coast defence and placed with the sea-going flotillas and
battle-fleets. In the short period of ten years the tonnage of
submarines has risen from 100 to over 1,000 tons, and the range of
action from 400 miles at economical speed to 5,000 miles. Exactly what
this means is more easily realized when it is stated that the earlier
types of submarines could scarcely cross the English Channel and return
without taking in supplies of fuel, and in rough weather were forced to
remain in harbour, whereas the modern vessel can go from England to
Newfoundland _and back_ without assistance, and can remain at sea in
almost any weather, as was first demonstrated by the successful voyage
of the British submarines A.E.1 and A.E.2 to Australia, and has since
been proved by the operations of the British submarine flotilla in the
North Sea.
In addition to the cruising range there is, however, the question of
habitability. In this respect the progress has been equally as rapid. In
the older boats no sleeping accommodation was provided for the crew, and
food supplies and fresh water sufficient only for a few days were
carried. In the latest British, French and German vessels proper
sleeping and messing accommodation is provided, and supplies of all
kinds and in sufficient quantity to last a month are carried. Although
work on these craft is still very cramping for the crew, the increase in
the deck space and in the surface buoyancy has greatly minimised the
discomforts of service in the submarine flotilla.
With regard to safety, it has already been shown that a submarine is
only held below the surface by the power of her engines and the action
of the water on her diving-rudders. This means that in the event of
anything going wrong _inside_ the vessel she would automatically rise to
the surface; but should the hull be pierced in any way, either by shot
or by collision, and an overwhelming inrush of water result—overcoming
the buoyancy quickly obtained by blowing out the water-ballast
tanks—then the vessel must inevitably sink, and the question of whether
or not the crew can save themselves becomes a problem to which no
definite answer can be given, although a special means is provided in
all modern vessels belonging to the British Navy. Speaking generally, it
may, however, be said that if the disaster occurs suddenly, and the
vessel sinks into very deep water rapidly, the chances of life-saving
are extremely small; but if the water is comparatively shallow, as along
the coast (100 to 150 feet), the likelihood of many of the crew being
able to save themselves with the aid of the _special escape helmets and
air-locks_ is fairly good.
We now come to the most important improvement made in the fighting
qualities of these vessels since first they came into being, viz. the
wonderful increase in the surface and submerged speed. In the older
craft the surface speed did not exceed 8 to 10 knots an hour, whereas it
now amounts to 16 to 20 knots, and the submerged speed has risen from 5
knots to 10 to 12 knots. It is a little difficult for any but a naval
man to realize exactly what this increase in the speed of submarines
really means, and it is equally as difficult to adequately describe it
here in non-technical language. It is a mere platitude to say that in
order to attack a surface warship the submarine must first get within
torpedo range of it; and yet it is on this very point that the strategy
and tactics of submarine warfare revolve. A clever naval tactician once
described the submarine as a “handicapped torpedo-boat.” The two points
on which he based this opinion were—the (then) slow speed of these
vessels compared with that of the surface warship, and its almost total
blindness when submerged. These two defects were for some years the
principal drawbacks of all the submarines afloat; but since that naval
expert pronounced submarines to be “handicapped torpedo-boats,” great
changes, great improvements have been made. The speed of the submarine
has increased by over 100 per cent., and they have been given longer and
wider range of vision by the introduction of two and three improved
periscopes instead of one elementary instrument. Nevertheless, the speed
difficulty is still a very real one, as will readily be seen when it is
taken into consideration that the speed of a submarine when attacking
submerged is frequently only half, or even a third, of that of her
enemy. In order to more clearly illustrate this and lift for a moment
the veil of secrecy which enshrouds the methods of attack adopted by
this type of craft, it will be necessary to describe what is known as
the_ right-angle attack_.
ATTACKING AT RIGHT ANGLES.
The difficulty of attacking a surface warship steaming at right angles
to the course of the submarine will be clearly understood by referring
to the following diagrams. The first shows an attack on a warship
travelling at 20 miles an hour, such as a big battleship or a cruiser
Any increase in the speed of the surface vessel not only adds to the
difficulty of the attacking submarine, but also the direction from which
the attack must be made. This feature is shown in the second diagram,
which illustrates a submarine attack on a vessel steaming at 30 miles an
hour, such as a fast destroyer or fleet scout. On the other hand, a
decrease in the speed of the on-coming surface vessel tends to either
make easier the task of the attacking submarine, or else to increase the
distance from which the attack can be delivered. This is shown in the
third diagram, which assumes the speed of the surface vessel to be only
15 miles an hour, such as a merchantman, troopship, food-ship, collier,
or old warship.
[Illustration:
RIGHT-ANGLE ATTACK BY SUBMARINES.
]
FIG. 1 represents a submarine attacking a hostile warship (or fleet)
steaming at 20 (statute) miles an hour. “A” is the line of vision. The
submarine sights the warship at a distance of just over 11 miles on her
port bow. “B” shows the hostile vessel’s course, which is 10 miles to
point marked “C,” and each division beyond equals 1 mile.
Directly the submarine, which is assumed to be lying in an _awash
condition_, sights the object of attack, she totally submerges and
steers forward at a speed of 10 miles an hour. The loss, and gain, of
the submarine on the different courses, can be seen in the table above
the chart.[7]
The spaces between the black dots show the most favourable points of
attack. It will be noticed in the table that both vessels are equal at
point “C,” but for many reasons this is not the best point of attack.
The gain of about six minutes on the longer course enables the submarine
not only to manœuvre into the best possible position for the attack, but
also to discharge more than one torpedo if necessary.
FIG. 2 shows the extreme limit at which a submarine could, with
reasonable chances of success, attack a destroyer, or other vessel,
steaming at 30 (statute) miles an hour, having sighted her at a distance
of 16 miles in the position shown by the line of vision “A.”
The distance to “C” is 15 miles for the surface vessel, and 5 miles for
the submarine. Here, again, the two vessels would be equal; but the most
favourable point of attack is shown by the two black dots—where the
submarine has gained two minutes.
FIG. 3.—The submarine sights the object of attack at a distance of 14 ¼
miles, in the position shown by the line of vision “A.” The surface
vessel has a speed of only 15 miles an hour (merchantman). In this case
the surface vessel accomplishes the 10-mile journey along course
“B”—arriving at point “C” 20 minutes in advance of the submarine. The
table shows how the submarine, by changing her course and “throwing” the
surface vessel on her beam, gradually reduces the loss, until, at the
point marked with the two black dots, she is but 4 ½ minutes behind. At
this distance she could fire her torpedoes at long range, with some
likelihood of success.
Although these charts show approximately the extreme limits of the
right-angle attack, a submarine could, of course, proceed for some
distance on the surface at a much faster speed; but considering the rate
at which the two vessels would be approaching each other, the submarine
which attempted it would run considerable risk of being detected, and
thus destroy her chances of a successful attack. Considering also the
time lost in sinking from the “light” to the totally submerged
condition, in coming to close quarters, the gain in speed would not
amount to as much as may at first seem probable.[8]
These charts are drawn and calculations made assuming the following
points:—
(1) The weather—fine and bright.
(2) Not taking into consideration strong tides, currents, etc.
(3) The enemy on the alert.
(4) Submarine waits at point “D” in an awash condition.
(5) Owing to 1, 2, and 3 above, the submarine travels from point “D”
in all courses in a submerged condition.
The most favourable position for a submarine flotilla is to manœuvre
close up to a fleet at anchor, or to get within 1,000 yards of a
fleet—steaming across its course; but both of these ideal positions for
attack are extremely difficult to obtain, and consequently in all the
less favourable positions speed is the deciding factor. Strategems will
undoubtedly play an important part in submarine warfare. An example of
this has already been afforded when the German submarines resorted to
the dishonest trick of laying in wait behind a trawler engaged in laying
mines, over which _the flag of a neutral state_ had been hoisted as a
blind. This resulted in the loss of three British cruisers with over
1,000 lives. It would, however, be quite in accord with the rules of
_civilised_ warfare for a submarine to shelter behind a “decoy”; to
attack simultaneously with a seaplane; or to approach an enemy behind
one of its own merchant ships.
THE PORPOISE DIVE.
The manœuvre known as the “Porpoise Dive” is merely the sudden rising of
a submarine in order to enable her commander to get a better view of the
surface than that afforded by the periscope. The submarine on
approaching the object of attack rises quickly to the surface by the
action of her horizontal rudders, then dives again, only remaining above
water for a few seconds to enable her commander to get a glimpse of the
enemy, and to take bearings. The submarine can then get within
torpedo-range, with simply the tiny periscope projecting from the
surface. This manœuvre is now seldom necessary, owing to the long and
wide range of vision of the two or three periscopes fitted in modern
submarines.
DIFFICULTY OF THE FIXED TORPEDO TUBE.
With the exception of one or two vessels, which it would be unwise to
specify, all the submarines engaged in the present war have what are
called _fixed submerged tubes_. This means that the tubes from which the
torpedoes are discharged are fitted _inside_ the submarine _on a line
with the centre of the boat_, and cannot be moved or aimed in any way
apart from the boat itself. It therefore becomes necessary for the
submarine to be _aligned_ by the steering rudders on the object of
attack before the torpedoes can be discharged. In simpler vein,
torpedoes can only be fired by a submarine straight ahead or straight
astern. Hence a submarine, with a hostile warship coming up on its beam,
is compelled to turn and face its opponent (or turn its stern towards
her) before delivering an attack.
SUBMARINE FLOTILLA _v._ SURFACE FLEET.
It is absolutely necessary for submarines acting in company to have each
its allotted task; and for a wide space of water to be left between each
boat; as it is impossible, at present, for one submarine to know the
exact position of another when both vessels are submerged. Therefore, if
each boat was not previously instructed how to act, there would not only
be the likelihood of the greater portion of an attacking flotilla firing
their torpedoes at one or two vessels of the hostile fleet and allowing
the remainder either to escape or to keep up a heavy and dangerous fire
unmolested, but also of collision and of torpedoeing each other by
accident. There is no means of inter-communication between submarines
when submerged, and a battle between submarines is almost impossible.
SURPRISE ATTACK.
In this case invisibility is the element of success. Admiral Sir Cyprian
Bridge, G.C.B., in a letter to the Author once said: “When submerged the
concealment of the submarine is practically perfect. If she has not been
sighted up to the moment of diving, she will almost certainly reach,
unobserved, the point at which she can make her attack.” And this
opinion—shared for many years by all experts—has been amply proved in
the present war.
A submarine must, however, blend with the surrounding sea in its
ever-varying colours, lights and shades, in order that she may be as
invisible as possible when cruising on the surface. The French Naval
Authorities experimented off Toulon with a luminous paint of a sea-green
colour; but this, although causing the hull to be almost totally
invisible in certain weather, was found to be useless, as, on a bright
day with a blue sky, the green showed up clear against the bluish tint
of the surrounding sea. After many months of experimenting, a pale,
sea-green, non-luminous paint was chosen as the best colour for French
submarines. The British Admiralty also carried out a few experiments in
this direction, and came to the conclusion that a dull grey was the most
invisible shade. The German authorities decided in favour of a
grey-brown.
When travelling submerged, with only the thin periscopic tube above the
surface, it is almost impossible to detect the approach of a submarine
_before_ she gets within torpedo range; and when cruising on the surface
she is equally as invisible at a distance of a few miles. These
qualities enable the submarine in nearly all cases where her speed
permits, to effect a surprise attack on a hostile battleship or cruiser
_when not closely screened by fast destroyers_, whose duty it is to be
ever on the watch for submarines.
As to the tactics which would be employed by a submarine (or flotilla)
in attacking a hostile warship (or fleet), it is impossible to say, for,
like the impromptu attacks of all “mosquito craft,” the exact method, or
manœuvre, is arranged to suit the circumstances, and it is very seldom
that two such attacks are carried out alike. Generally speaking,
however, a hostile warship could be easily sighted, on a fairly clear
day, from the flying-bridge of a submarine at a distance of 10 miles;
but it would be practically impossible to detect the submarine from the
deck of a warship at that distance. On sighting her object of attack the
submarine would sink to the “awash” condition, and proceed for from 2 ½
to 5 miles, as might be deemed expedient. She would then submerge and
steer by her periscopes, each of which has a field of vision of 60
degrees. He would be a very keen look-out who would be able to detect
the few square inches of periscopic tube at a distance of three miles.
As this distance lessened, it might be advisable, if the sea was _very_
calm and if the object of attack was stationary, for the submarine to
slacken speed, so as to prevent any spray being thrown off by the
periscopic tube. Assuming, however, that the optical tube was seen by
the enemy, it would be extremely difficult to hit it with gun-fire at a
distance of one or two miles, or to damage the boat itself, which would
probably be immersed to a depth of 12 or 15 feet. At a distance of about
2,000 yards, or just over one mile, the submarine would discharge her
first torpedo, following it up with another at closer range from the
second bow tube. A rapid dive would then probably be necessary in order
to avoid the hail of shot which would plough up the waters around her.
If the first two torpedoes missed their mark the submarine might either
dive completely under the object of attack and then fire her stern tubes
at close range, or else manœuvre below the surface for an attack from
some other point.
One of the effects produced on fleets or individual warships in war time
by the ever present possibility of submarine attack is, however, that
they never remain at anchor or even stationary in an exposed position,
and seldom—if wise—proceed without destroyers as advance and flank
guards. These precautions double the difficulties of a successful
submarine attack.
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Footnote 7:
As it is almost impossible for a submarine, when totally submerged, to
steer a _perfectly_ straight course, the table above each chart shows
the approximate average loss and gain on each mile. It must also be
remembered that the submarine in actual practice need only reach the
torpedo firing line.
Footnote 8:
“Submarines of the World’s Navies.” By Charles W. Domville-Fife.
(London: Francis Griffiths.)