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CHAPTER I
The
Pre-war British Submarine Fleet
References
IN THE MID-SUMMER
OF 1939, immediately prior to the outbreak of the Second World
War, the Royal Navy possessed fifty-seven submarines. Twelve of
these were elderly, designed and laid down during the First World
War but completed after the Armistice1.
The rest were of what was known at the time as new construction,
designed and built in the period between the wars. They were broadly
of six different types. The most numerous and oldest group were
the eighteen boats of the O, P and R-classes which were large
patrol submarines intended for operations in the Far East. They
were of long endurance and had, for a submarine, good accommodation
but had never realised their designed performance, furthermore
they had external fuel tanks that tended to leak2.
The three very large River class which, chronologically, came
next were designed with a surface speed high enough to accompany
the fleet and it was hoped that they would be able to take part
in a fleet action. They suffered, however, from the same defects
as the O, P and R-classes and proved too slow for the purpose
3. The Rivers were followed by a class of six new minelayers
of the same size as the O-class that could carry many more mines
than earlier types of minelaying submarines4.
All these types of submarine were large and in the early thirties
it was decided to produce a smaller patrol submarine for use in
home waters and the Mediterranean. Twelve of the S-class of the
same size as the successful First World War E-class were built.
The S-class were not of high performance but had internal fuel
tanks and were handy and reliable. The latest designs were the
T and the U-classes, the leading units of which had just come
into service. The T had the same endurance as the O-class but
was smaller and, like the S-class, carried its fuel internally.
It also had a more powerful torpedo armament so that it could
attack at longer ranges. Otherwise its performance was only that
which the O, P and R classes achieved in service but they were,
above all, reliable. Three T-class had been completed and were
doing their trials and another twelve were in various stages of
construction. The original intention in the U-class was to produce
an unarmed training submarine to replace the rest of the H-class.
With the gathering war clouds, however, the final design that
emerged was of a small patrol submarine that was also suitable
for training5
The British
Government had been severely shaken by the depredations of the
German U-boats during the First World War and had campaigned vigorously,
especially at the Washington Treaty negotiations in 1922, for
the total abolition of the submarine from the world's navies.
They failed in this only because of the opposition of the United
States and France, but they made headway in restricting the operations
of submarines against merchant vessels. Progress with this policy
was continued in the London Naval Treaty of 1930 and in the Anglo-German
Naval Agreement of l935. British submarines were therefore designed
primarily for attack on warships. All were armed with the 21 torpedo:
the "new construction" submarines with the new Mark
VIII burner type with a warhead of 750 lbs of high explosive,
and the older boats with the wet heater type Mark IV with a warhead
of 500 lbs. All of the "new construction" submarines
could fire a bow salvo of six torpedoes6.
All except the dozen submarines of First World War vintage were
therefore capable of sinking the most powerful warships afloat.
The six minelaying submarines carried fifty moored contact mines
as well as a salvo of six bow torpedo tubes.
The larger
classes of submarine mounted a four-inch gun in a rotating breastwork
with quick manning hatches. The S-class mounted a three-inch gun
on the fore casing and the U-class could also do so if they sacrificed
two reload torpedoes. The elderly H-class had no gun. The purpose
of a gun in a submarine was to make it possible to sink small
vessels not worth a torpedo or too small to hit with a torpedo
and also to enforce orders to merchant ships.
An asdic set
was fitted in all submarines except eight boats of the H-class7.
This instrument was mainly used as a hydrophone for listening
but could also be used for communication between submerged submarines
or for echo detection of another submerged submarine.
All submarines
had a wireless loop aerial which could receive low frequency
signals from Rugby wireless station when totally submerged in
home waters or the Mediterranean. New construction submarines
could send messages by high frequency wireless from anywhere
in the world to the Admiralty shore network of receiving stations.
In general, however, this could only be done when the submarine
was on the surface as the mast aerial with which new construction
submarines were fitted for use from periscope depth proved to
be only of short range and so of very little value.
Taking fuel,
fresh water, provisions and living conditions into consideration,
the larger submarines of the O, P and R-classes, the Rivers,
and the minelayers as well as the new T-class could remain at
sea for a period of some six weeks. They could operate at about
two thousand miles from their base. The medium sized submarines
of the S and L-classes could keep the sea for a month or so
and operate at about a thousand miles from their base, while
for the small submarines of the H and U-classes the figures
were a fortnight and five hundred miles.
In all classes
of submarine, the electric storage batteries had the capacity
to drive the submarine at slow speed (two knots or so) for
a period of twenty-four hours with a margin for making an
attack or two or taking evasive action. It was then necessary
to re-charge the batteries on the surface for a period of
some six hours. Submarines therefore had no difficulty in
staying down during daylight hours but it was essential to
have time to re-charge on the surface every night.
There were
two ways to detect the enemy when running submerged. The first
was by periscope and this could be used in daylight to sight
ships and aircraft at whatever distance visibility or the curvature
of the earth permitted. Periscopes, however, were of no use
at night or even in twilight. There was also a limit to their
use in rough weather both because of the height of the waves
and the difficulty of keeping the submarine accurately at the
right depth8. The
second method of detecting the enemy was by asdic. This was
normally used passively, that is, simply by listening for the
noises made by ships propellers9.
It was the only way to detect that ships were about when the
submarine was running submerged at below periscope depth. Usually
in good visibility by day the periscope would see the enemy
first but in bad visibility asdic would often give the first
warning. On the surface, both by day and night, the only way
to detect an enemy, whether a ship or an aircraft, was by lookouts
using binoculars. On the surface asdics was of little use to
detect ships10.
By far the
most effective way to make a torpedo attack was from submerged
using the periscope but this could only be done in daylight.
The target could then be positively identified, the course and
speed plotted and ascertained and the torpedoes accurately aimed.
However in calm weather the torpedo tracks might well be sighted
in time for the target to take avoiding action. Manoeuvring
to attack also required considerable skill11.
At night, when nothing could be seen through the periscope,
a torpedo attack had to be made on the surface. It was then
harder to identify the target, to estimate range, course and
speed and there was always the danger that the submarine would
be sighted. However submarines were faster on the surface than
submerged and had a better chance to close distant targets.
Attacks could also be made with the submarine dived deeper than
periscope depth by using asdic but this method was the least
accurate of all and the chances of success were low.
Passage-making
in wartime could be made most expeditiously by running on the
surface using the diesel engines day and night. A distance of
some 300 miles could thus be made in twenty-four hours12.
Proceeding on the surface by day was, however, hazardous when
attack by aircraft or enemy submarines was likely. Passage making
under these conditions was therefore normally made by proceeding
submerged by day and only running on the surface at night. This
reduced progress to about 130 miles in twenty-four hours or
half that obtained by going on the surface continuously.
WE MUST NOW
TURN to questions of personnel and the manning of submarines
in the Royal Navy. On the outbreak of war, there were six flag
officers on the active list qualified in submarines13.
All had distinguished themselves in command of submarines during
the First World War. The higher ranks of the Royal Navy therefore
had plenty of submarine advice to turn to if they wished to
use it. Four of these officers had held the appointment of Rear
Admiral (Submarines)(RA(S)) but the other two were now too senior
for the post. The Admiralty had therefore in 1939 appointed
Rear Admiral BC Watson CB DSO to be RA(S). Admiral Watson had
never served in submarines and had spent his career in general
service as a specialist in navigation14.
He had been awarded the DSO in 1917 after an action with German
destroyers in the North Sea when serving as Navigating Officer
to Commodore Tyrwhitt in HMS Centaur.
There were
thirteen submarine specialists in the list of post Captains
and five of these were employed in the submarine command in
1939. The most senior (Captain CAB Coltart RN commanding the
Fifth Flotilla at Fort Blockhouse) had commanded submarines
throughout the First World War and the Chief Staff Officer (Captain
IAP MacIntyre RN) had had some war experience in command in
1917-18. The other three (Captain GMK Keble-White RN in the
Fourth Flotilla, Captain P Ruck-Keene RN in the First Flotilla
and Captain WD Stephens RN in the Second Flotilla) gained their
first commands during the twenties and their experience had
been obtained in peacetime between the wars. This was also true
for Commander JS Bethell RN who commanded the Sixth Flotilla.
There were thirty-four submarine specialists who held the rank
of Commander and five of these officers were actually in command
of submarines. Normally there was one Commander in command of
a submarine in each flotilla who, as Senior Submarine Officer
also answered to the Captain(S) for certain administrative duties.
The Commanding Officer of the surface tender, usually a destroyer
or sloop, used mainly as a target for submerged torpedo attacks,
was also normally a Commander qualified in submarines. A few
other Commanders who were submarine specialists, were employed
in staff appointments in the Admiralty and elsewhere to do with
submarines and the remainder were in general service.
The rest of
the submarines were commanded by twenty-nine Lieutenant Commanders
and fifteen Lieutenants. These officers were mostly in their
thirties although some of the younger ones might be in their
late twenties and some of the older ones just over forty. Command
was normally achieved after serving for five or six years in
submarines graduating progressively from Navigating or Torpedo
Officer of a submarine to First Lieutenant, initially of a small
submarine and then of a larger boat. Officers normally entered
submarines as Sub Lieutenants in their early twenties after
completing their courses for Lieutenant and having obtained
a watchkeeping certificate. The officer's submarine course lasted
three months and was taken at Fort Blockhouse where the submarine
school was situated.
Before being
appointed in command of a submarine, officers had to be selected
for and to complete the Commanding Officers Qualifying Course.
It lasted three months in the Fifth Flotilla at Fort Blockhouse
and was almost entirely taken up in training for making submerged
torpedo attacks. Some of this was done in a simulator known
as the submarine attack teacher and some at sea in submarines
of the Fifth Flotilla. Considerable emphasis was put on safety
during peacetime exercises. The course was supervised by an
experienced submarine commanding officer specially appointed
and who answered to Captain(S), Fifth Submarine Flotilla. After
a year in command, normally of an anti-submarine training submarine
in home waters, the submarine commanding officers returned to
general service for a full two year commission in a battleship
or cruiser and in 1939 no less than thirty-two officers were
so employed. After this they returned for command of a larger
submarine as a Lieutenant Commander and continued in command
of successive submarines until either they were promoted to
Commander or were passed over for promotion.
The ratings
who formed the submarine crews were, like the officers, almost
without exception, volunteers. They were long service ratings
enlisted for twelve years or to complete time for pension and
had to be in the very good category for conduct. They were trained
in their specialist duties such as torpedo, gunnery, engineering,
and communications in the naval schools before being selected
for service in submarines. They were then sent for a six-week
submarine course at Fort Blockhouse that included Davis Escape
training, before being sent to a submarine.
In reserve
there were twenty-three junior officers of the Royal Naval Reserve
who were qualified in submarines. Being professional seamen
in the Merchant Navy they were well suited to send to peacetime
training submarines as navigating officers when they became
operational in war. There were also some 450 men of the Royal
Fleet Reserve who had left the Navy after twelve years service
who had been in submarines.
The numbers
actually manning the submarines of the Royal Navy totalled some
two hundred and seventy officers and two thousand five hundred
men and this figure includes spare crews in each flotilla and
the number required as a drafting margin as well as those under
training. The ships companies of the four depot ships and the
shore base at Fort Blockhouse, who were from general service,
amounted to another two hundred and fifteen officers and two
thousand men. This total of some five thousand needed to man
and support the submarine branch was 3.9% of the total strength
of the Royal Navy and Royal Marines, which stood at 129,000
in mid 1939.
THE PEACETIME
ORGANISATION of the submarines of the Royal Navy15
was presided over by RA(S) who flew his flag at the submarine
base at Fort Blockhouse at Gosport. He was responsible, subject
to and in close co-operation with the Admiralty for all matters
connected with submarines notably for the staff requirements,
development and trials of new submarines and for the selection,
training and drafting of all submarine personnel. He had full
command of the training flotillas at Portsmouth and Portland but
the three operational flotillas were under the command of the
station Commanders-in-Chief. RA(S) was available to advise these
Cs-in-C and exercised a degree of technical administration for
them.
The First
Submarine Flotilla, consisting of the depot ship Maidstone
with three of the large River class Fleet submarines and four
of the S-class, formed part of the Mediterranean Fleet and was
based at Malta. The Second Flotilla consisting of the new depot
ship Forth
with three minelaying submarines and two of the S-class similarly
formed part of the Home Fleet and was based at Devonport. These
two flotillas accompanied their fleets on their cruises and took
part in all their major exercises. They also provided targets
for asdic fitted ships of the fleets to practise upon. In most
of the exercises, they were the enemy and the exercises were framed
to practise anti submarine measures rather than for pro-submarine
purposes, although, of course, they were often of considerable
value for both sides. The powerful Fourth Submarine Flotilla consisted
of the large depot ship Medway,
thirteen boats of the O, P and R-classes and two minelayers and
was on the China Station. On this station the ships were generally
dispersed on various duties and there were few fleet exercises.
The submarine flotilla was therefore able to follow its own annual
programme. It was based in winter at Hong Kong and in summer at
Wei Hai Wei in north China with a visit south each year for the
major exercise for the defence of Singapore. It therefore had
much more time for purely pro-submarine exercises than the other
two operational flotillas.
The Fifth
Flotilla was based at Fort Blockhouse at Gosport and here, as
we have already seen, were the Headquarters of RA(S), the submarine
training organisation and the depot. The flotilla included three
distinct groups of submarines. The first of these was the local
flotilla of five assorted submarines, which spent most of their
time in personnel training and also undertook many trials and
miscellaneous duties. The second group was composed of new submarines
undergoing their trials and working up their ships' companies.
The third group consisted of eight submarines in running reserve.
These reserve boats had one crew between three, who took each
boat to sea in rotation. The flotilla also administered the crews
of the submarines in the building yards or undergoing a long refit
in the home dockyards. The Sixth Submarine Flotilla was based
at Portland with the elderly depot ship Titania
and consisted of eight assorted submarines of the smaller
types whose duty was to provide targets for the training of asdic
operators and for the work of the Asdic Experimental Establishment.
A reserve group of three submarines was also attached to this
flotilla.
Of the five
flotillas it has been seen that one, the Fifth, was shore based
at Fort Blockhouse in Gosport while the other four were supported
by Submarine Depot Ships. The submarine crews when in harbour
lived in the depot ships which were fitted with workshops to
maintain their submarines and also carried fuel, torpedoes and
stores for their support. Three of the depot ships were new
but one was still an elderly converted merchant ship. Three
other elderly depot ships were refitting or in reserve and another
new one was under construction16.
All British
submarines were kept in good material condition by periodical
refits in the dockyards. At any one time, about eight or ten
submarines were so occupied. The refits were carried out at
Malta, Singapore and Hong Kong as well as in the home dockyards.
When in commission or reserve, regular full power engine trials
were carried out as well as battery capacity discharges and
dives to the maximum diving depth. Torpedoes were regularly
run with practice heads. In this way all submarines were kept
fit for operations. The H-class, however, now nearing twenty
years old, with a shallow maximum diving depth, a slow surface
speed and a poor wireless installation were only fit for operations
in an emergency. However in 1939 all of the H-class were due
for replacement within a year.
In peacetime,
submarines were normally kept full of fuel, lubricating oil
and fresh water. Except for an emergency stock of fourteen
days hard tack provisions, food was only embarked as required
by the programme being followed. One full salvo, generally
of six torpedoes was kept in each submarine fitted with practice
heads, the warheads for which were stowed on board in the
gun magazine. There was therefore only room for a few rounds
of gun ammunition. The reload torpedoes were kept in the depot
ship or ashore. A submarine when on her own could, therefore,
in emergency, prepare one salvo of torpedoes on board for
running with warheads. Full preparation for war could only
be done in a naval base or in company with a depot ship and
involved embarking a full outfit of torpedoes with warheads
and a full outfit of gun ammunition as well as of provisions
and also topping up with fuel, lubricating oil and fresh water.
For a depot ship to prepare her whole flotilla for war simultaneously
needed considerable organisation and this was exercised from
time to time.
Many of the
supplies required by submarines in war, such as diesel fuel,
lubricating oil and provisions were readily available in naval
bases and civil ports. Torpedoes, mines and ammunition, however,
were peculiar to submarines and had to be specially manufactured
and supplied to them17.
The scale of provision of torpedoes in the period between
the wars was a full load of torpedoes for each submarine with
a reserve of one hundred per cent. For instance twelve torpedoes
were provided for each of the H-class and twenty-eight for each
of the O, P and R-class. The total number of submarine torpedoes
required by this scale in 1937, including those for four new
submarines completing, was 1264. Half of these were required
to fill up the submarines and half were in reserve. This total
would increase with the new submarine building programme and
by 1941 it would be 1660 and all would be of the new Mark
VIII. In 1937 the Admiralty reviewed the provision of torpedoes.
The total production of the three torpedo factories in the United
Kingdom18 was
2000 and this included those for ships and aircraft as well.
The intention was on the outbreak of war, to order another reserve
of 100% of the outfit torpedoes and also the scale for the new
submarines of an emergency war programme and this would total
more than the output of the three factories. Financial considerations
in 1937 were still important and so the Admiralty sought to
reduce the scale for the provision of torpedoes rather than
to increase it. They pointed out that only 575 torpedoes had
been fired in action by our submarines during the First World
War. Admittedly the German U-boats had fired 2695 torpedoes
in their campaign but most of these were at merchant ships,
a strategy that was now forbidden by International Law. The
Admiralty therefore suggested that the scale of reserve torpedoes
should be halved and kept at 50% of the outfit. It was considered
safe to do this, as there were some 719 Mark
IV torpedoes in stock, 404 of which were surplus to the
scale and which could be kept as an emergency reserve. RA(S),
however, after pointing out that submarines now fired larger
salvoes, managed to get this changed to a reserve of 75% of
the outfit for submarines19.
The plan was then still to order a duplicate reserve of 1000
torpedoes on the outbreak of war as well as outfit torpedoes
for new submarines of the emergency war programme.
THE TRAINING OF BRITISH SUBMARINES for war can
only be described as patchy. Training in making submerged torpedo
attacks by day was excellent both of individual officers when
qualifying for command and for submarines in commission. This
was by far the most common exercise carried out. Simulators
or "attack teachers" as they were known, were valuable
training devices and were installed in all depot ships and in
the submarine base at Fort Blockhouse. The only defect in attack
training was in spreading of salvoes of torpedoes. Spreading
of full salvoes against warships was understood and practised,
but the use of reduced salvoes of two, three or four torpedoes
had not been studied. This is perhaps understandable as British
submarines were not expected to attack merchant ships for which
such reduced salvoes were mainly required. On the other hand
training in night torpedo attacks on the surface was at best
poor and at worst nonexistent. The reason for this was the fear
of collision leading to the probable loss of a submarine20.
A few exercises were carried out with dimmed navigation lights
burning on one side or the other but this rendered the practice
totally unrealistic. Practice torpedo attacks by asdic were
sometimes undertaken but were not properly analysed and few
Commanding Officers had any confidence in this method. Crash
diving from the surface and diving deep from periscope depth
to avoid being rammed were exercised ad nauseam but the
training of lookouts by day against aircraft or at night against
darkened ships was extremely poor. The use of the gun in a surprise
attack from submerged was frequently practised and British submarines
were well ahead of other navies with this tactic. The exercise
of submarines in long patrols was just satisfactory during fleet
exercises by the three operational flotillas but the only chance
the training submarines got was during the period of an exercise
known as Rear Admiral (Submarines) War which took place each
summer. A certain amount of practice in evasion of anti-submarine
measures was obtained during exercises with asdic fitted ships.
The main hope of survival in war, however, was based on optimism
and knowledge that hydrophones had proved of little use against
U-boats in the First World War and there were no indications
that asdic had been developed by any of our potential enemies21.
IMMEDIATELY
AFTER THE First World War, planning for the use of British submarines
in a future war received a severe setback when the Government
proposed at the Washington Conference that submarines should be
abolished. Although abolition was not accepted, the subject was
in any case rendered far from urgent by the imposition of the
ten-year rule22. British
naval strategy was still firmly based on the battlefleet as the
arbiter of sea power but surprisingly submarines were, in this
period, given an important strategic role. The Anglo-Japanese
Alliance, which had relieved the Royal Navy from keeping a battlefleet
in the Far East for nearly twenty years, came to an end at this
time. The Washington Naval Treaty concluded in 1922 reduced the
Royal Navy to an extent that it could not hope to keep a battlefleet
permanently in the Far East. Should war with Japan threaten, a
battlefleet would have to be sent from European waters to Singapore
where it would provide the backbone for the defence not only of
Malaya, but also of Australia, New Zealand and India and even
our African possessions. In 1919 twelve submarines were sent east
to be permanently based there in order to to hold the fort"
until this battlefleet could arrive. This submarine flotilla,
now of more modern boats specially built for the purpose, was
still on station in the midsummer of 1939.
The ten-year
rule was cancelled in 1932 and the coming to power of the Nazi
party in Germany in the following year led to the urgent revision
of war plans. When the Abyssinian crisis broke in 1935, the First
Flotilla consisted of three of the Thames-class and three of the
S-class and it was then reinforced by three more S-class from
home and two O and two P- class from the Far East. In addition
the Second Flotilla consisting of the depot ship Lucia
and four of the L class had been sent to Aden. A new Third
Flotilla consisting of Titania,
three S-class and a minelayer had also been formed to go to Gibraltar.
When revising his plans for war with Italy after the crisis, the
C-in-C Mediterranean asked the Admiralty for twenty-one submarines
which he needed to assist his fleet. The Admiralty replied that
no more than thirteen would be available and he must plan accordingly.
In the Far East, policy remained unchanged and fifteen submarines
were kept on the station. Just before the war, in the summer of
1939 the Committee of Imperial Defence asked the Admiralty if
it could increase the submarine strength in the Far East, but
this was not so much to protect Singapore as to provide a means
to interfere with Japan's attack on China. Far from it being possible
to concentrate submarines in home waters against Germany, therefore,
there were calls at the time to send more submarines abroad.
In the same
way as the Abyssinian crisis had put submarine war plans against
Italy to the test, the Munich crisis in the autumn of 1938 focused
attention on the war plans against Germany. In this latter emergency
the Royal Navy was mobilised and the Home Fleet was sent to its
war stations in the North Sea. Submarines in reserve were commissioned
and the Home Fleets flotilla, the Second, with its depot Lucia
was sent to Aberdeen. It was reinforced by another flotilla,
the Third, with the depot ship Titania
from Portland and stationed at Blyth. The two minelaying submarines
of the Second flotilla were transferred to Blyth and replaced
by three S and two H-class boats from the Fifth and Sixth flotillas23.
The Fifth Flotilla at Gosport took over all other submarines in
home waters including those commissioned from reserve, which were
used mainly for training.
In the Munich
crisis the submarines were issued with sealed orders direct from
the Admiralty but the submarines were not sent to sea and the
crisis was over before the orders had to be opened24.
No copies of the orders have survived in the records but it is
known that Porpoise
and Narwhal
were to lay mines in the estuaries of the Elbe and the Weser.
It is probable that the submarines of the Third Flotilla would
have been sent to patrol in the Heligoland Bight and the Second
Flotilla to the Skagerrak or Kattegat with orders to report any
German warships that put to sea.
With the near
success of the German submarine campaign in the First World War,
anti-submarine measures in the Royal Navy were clearly of the
greatest importance. All destroyers and sloops and many smaller
anti-submarine vessels were being fitted with asdic and the antisubmarine
training of these ships was essential in war as well as peacetime.
A substantial number of submarines would clearly be required full
time for this function which could fortunately be done by out
of date and elderly submarines. The plans allowed for about a
quarter of our submarine strength to be used for training that
would therefore not be available for operations.
The Admiralty
issued new war plans early in 1939. These allowed for war against
Germany and Italy simultaneously with France as an ally. The plans
recognised that Japan was unfriendly and that it was necessary
to keep a defensive posture against her in the Far East. The war
plans for submarines, therefore, after commissioning the eleven
boats in reserve, provided for the reinforcement of the Mediterranean
with six submarines and for the fifteen submarines to remain in
the Far East. All the operational submarines left in home waters
would be concentrated in the North Sea as part of the Home Fleet,
leaving eight of the elderly H-class for training duties.
It was planned
that the two North Sea flotillas would be the Second from the
Home Fleet and the Sixth from Portland with their depot ships
Forth
and Titania.
RA(S) would take command of them under the C-in-C and would establish
an operational headquarters at Aberdour25.
The operational role of these flotillas was to form outposts off
the exits from the German bases in the Heligoland Bight and in
the Skagerrak to give warning should units of the German fleet,
especially the Pocket Battleships, attempt to break out onto the
trade routes. It was not expected, as in the First World War,
that we should receive radio intelligence of enemy movements and
RAF reconnaissance by Coastal Command was far from reliable. This
was due to a fear of fighters off the enemy coasts, prevailing
poor visibility in the North Sea and a lack of endurance of its
aircraft. Reconnaissance by our submarines was therefore important.
If this was to be their primary purpose, however, submarines would
often not be able to attack ships with torpedoes; a counter attack
by screening vessels would be likely to keep them submerged and
unable to signal by wireless for long enough to render the sighting
useless. The submarines on patrol, therefore, were given reconnaissance
as their primary aim and attack was to be secondary. Attack on
merchant ships had to be in accordance with the prize regulations,
which involved visit and search. Merchant ships could not be sunk
without making provision for the safety of the crew and this condition
was not considered to be met by leaving them at sea in the ships
boats. Naval auxiliaries and transports could be sunk without
warning but it was difficult to tell them from ordinary merchant
ships.
In the Mediterranean
the war plan involved the re-routing of shipping round the Cape.
For fear of air attack, Malta was to be abandoned as a fleet base
and the battlefleet was to be sent to Alexandria. Malta was to
be retained, however, as an air and submarine base. The depot
ship Maidstone
was to go to Alexandria with the fleet, taking one submarine
with her for anti-submarine training. The rest of the submarines
were to be maintained by the dockyard at Malta and a war submarine
depot on Manoel Island in Sliema Harbour. The Mediterranean flotilla
was to be reinforced by six submarines from the Home station but
it had been decided that the three very large fleet submarines
of the Thames-class would be better employed hunting for raiders
and their supply ships in the Atlantic than patrolling in the
Mediterranean. They were therefore to move to Gibraltar where
they would be based on the dockyard. War plans for the Mediterranean
divided responsibility between the French fleet, which was to
look after the western basin and the British for the eastern.
Italy was dependent on sea communications for imports and for
contact with her colonies. Sea communications with the outer world
would be cut effectively by holding the Suez Canal and the Straits
of Gibraltar. Three quarters of Italy's requirements in war could
be met from Europe although the capacity of the railways across
the frontier could only handle half of them. It was estimated
that if the Dardanelles route, by which vital oil from Romania
came by sea, were to be cut, then her stocks would soon run out.
The closing of this route was not easy. The tankers could keep
to neutral territorial waters until they had to cross to Italy
in the Otranto area. As submarines were restricted to the prize
manual rules of visit and search, operations to stop the traffic
so close to the Italian coast were obviously impractical. It was
also desirable to try to stop communications with Libya but again
the prize manual rules made it very difficult. In practice, therefore,
submarine operations in the Mediterranean could only be directed
against warships in the same way as in home waters. The submarines
were to act as outposts for the fleet with reconnaissance as their
first duty.
In the Far
East the peacetime force of fifteen submarines was to remain on
station, its function being unchanged. Here it was 'to hold the
fort' should Japan make a hostile move until a battlefleet could
be sent from European waters. In some ways its function was even
more important than before, since with Germany and Italy as enemies
and even with France as an ally, it would be difficult to find
a fleet large enough to oppose the Japanese Navy, and the submarines
might have to 'hold the fort' for some time. In the event of Japan
proving to be quiescent, however, it was intended to send four
boats to Aden to oppose the Italian Navy in the Red Sea. How the
submarines would have been used in the Far East is by no means
certain. They could probably have been disposed defensively in
the South China Sea, off likely landing places in Malaya and in
the approaches to Singapore. This would not only give warning
of the enemy's approach but also enable them to attack and by
attrition cut down his strength. Some submarines would probably
have been kept in the Hong Kong area not only to do as much damage
as possible but also to give warning of enemy movements south
through the Formosa Strait and the gap between Luzon and Formosa26.
IN SPITE THEREFORE of their wish, after the First
World War, to have the submarine abolished, the Royal Navy
possessed an efficient submarine fleet in the mid-summer of
1939. It was, however, the smallest of all the great naval
powers. The submarine fleets of the United States, France,
Italy and Soviet Russia were substantially larger than the
British; that of Japan marginally so, and that of Germany
was the same size. This in fact had the advantage that under
the Anglo-German Naval Agreement, a small British submarine
fleet also kept the German U-boat fleet small. Great Britain
had, however, succeeded in limiting the power of the submarine
in what it did best by legal restrictions in its operations
against commerce. Understandably, therefore, Britain's own
submarines were designed and intended for operations against
warships. For this purpose they had developed reliable submarines
of moderate performance with a powerful torpedo armament.
They were well trained in its use when submerged by day and
were capable of sinking the largest warships afloat. Well
before the cancellation of the ten-year rule they had foreseen
an important strategic role for submarines in the Far East.
Nevertheless they were thought by many to be most useful in
the Royal Navy to help develop and train anti-submarine forces.
In the years immediately preceding the Second World War, however,
an operational role similar to that in use in the First World
War was adopted for submarines in home waters mainly against
the pocket battleships and also against the Italian Fleet
in the Mediterranean. Their purpose was to act as outposts
for our own battlefleet in which reconnaissance and attrition
would assist it to come into action under favourable circumstances
and destroy the enemy.
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