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Chapter 12: Submarine Policy 1919 - 1930

12.1 Submarine Fleet 1919

1. At the conclusion of hostilities in November 1918 the submarine fleet consisted of (CB 1815 December 1918):

No of
1 B (B3)
29 C
3 D
29 E
4 V
3 F
10 G
10 H 1-20
11 H 21
6 J (including J7 - RAN)
14 K
1 M
15 L
6 R

2. The following boats had been ordered and most were building:

  • (a) M2 and M3 were building. M4 was scrapped.
  • (b) H13 and H16-20 of the second ten boats of the Hl-20 Class ordered from America were not delivered to this country.
  • (c) H31-34, 42-44 and 47-52 of the H21 Class were completed. Ten boats of the class had been or were scrapped.
  • (d) L18-33 were all completed except L28-32 which were cancelled and broken up after building had commenced. L34 and L35 were also cancelled.
  • (e) R2-4 and R10 were completed. R5 and R6 were cancelled.
  • (f) K26 was completed.
  • (g) Of twenty-five L50 Class ordered, only seven were completed.

3. As would be expected, many of the older boats were scrapped in the immediate post war years. By the end of 1919 the following had disappeared from the active list B3, all of the C Class except C2, C9, C10 and C12 which had gone by April 1920, the D Class, V Class and F Class and some of the E Class, G Class and K Class. By the end of 1920 the G Class had gone and only sixteen of the E boats remained. Over the next ten years the run down was much slower. By October 1932 of the boats ordered during the war fourteen H21 Class, twelve L Class, six L50 Class and R4 remained.

12.2 Washington and London Treaties

4. After the war there was a general desire for limitation in naval armament which resulted in the Washington Treaty in 1923 and the London Treaty in 1930. Discussions took place at Geneva in the late 1920's on limiting submarine displacement.

The Washington and London Treaties are explained in the following paragraphs insofar as those treaties affected submarines. Although the Washington Treaty dealt only with capital ships it gave a good indication of what could be expected to happen to smaller ship construction within a few years. Both these factors had their effect on submarine design during the 1920's in that it was essential to get the maximum possible in the smallest displacement at the minimum cost.

5. The Washington Treaty between the British Empire, France, Italy, Japan and the United States of America was signed in Washington on 6 February 1922 and ratified by the governments concerned on 17 August 1923. It was to remain in force until 31 December 1936. It contained a clause, 'in view of possible technical and scientific developments, the United States, after consulting with the other Contracting Powers, shall arrange for a conference of all the Contracting Powers which shall convene as soon as possible after the expiration of eight years, from the coming into force of the present Treaty to consider what changes, if any, in the Treaty may be necessary to meet such developments.'

From the beginning of 1922 therefore it was known that a further conference would be held about 1930 and it was generally accepted that limitations would be imposed on the smaller types of naval vessels.

6. The London International Treaty for the Limitation and Reduction of Naval Armament was signed in London on 22 April 1930 and ratified 27 October 1930 by the same powers as for the Washington Treaty. The following articles of the Treaty applied to submarines:

  • (a) No submarine with a standard displacement, exceeding 2000 tons or a gun above 5.1-inch calibre is to be acquired or constructed.
  • (b) A maximum of three submarines may be retained, built or acquired of a standard displacement not exceeding 2800 tons or carrying a gun above 6.1-inch calibre.
  • (c) Submarines already possessed on the 1 April 1930 having a standard displacement not in excess of 2000 tons and armed with guns above 5.1- inch calibre may be retained.
  • (d) A vessel shall not be replaced before it becomes over-age and for submarines this was 13 years after the date of its completion. The keels of replacement tonnage shall not be laid down more than three years before the year in which the vessel to be replaced becomes over-age.
  • (e) The completed standard tonnage of submarines which was not to be exceeded on the 31 December 1936 was 52 700 tons. Vessels, which cause the total tonnage to be exceeded, are to be disposed of gradually during the period ending 31 December 1936.
  • (f) The Treaty to remain in force until 31 December. 1936. The Contracting Powers' should meet again in 1935 to frame a new treaty.

Rules were laid down for the disposal of vessels of war whether by scrapping, conversion to hulks or to target use, and for experimental or training purposes.

7. The standard displacement, also called the Geneva displacement, of a submarine, as laid down in the London Treaty, was the surface displacement of the vessel completed (exclusive of the water in non-watertight compartments), fully manned, engined and equipped ready for sea, including all armament and ammunition, equipment, outfit, provisions for crew, miscellaneous stores, and implements of every description that are intended to be carried in war, but without fuel, lubricating oil, fresh water or ballast water of any kind on board.

8. Within one month after laying down a vessel, the party concerned had to report to each of the other parties concerned the date of laying down, the classification of the vessel, the standard displacement, the length at waterline, extreme beam and mean draft at standard displacement, and the calibre of the largest gun. Within one month of the date of completion this procedure had to be repeated giving the date of completion together with the foregoing particulars relating to the vessel at that date.

Particulars of all submarines existing at the time of signing the Treaty were, of course, exchanged between the participating parties.

9. For vessels building in 1930 and designs that followed, the standard displacement was calculated from the design figures. For existing submarines actual displacements and liquid capacities were used. In some cases slight adjustments were made in certain items such as ammunition carried, stores, etc to bring them to some sort of standard. Once a standard displacement had been published it remained unchanged. From 1930 until the end of the Treaty in 1936 only the standard displacement was quoted in such publications as CB 1815 and it was sometimes called the surface displacement. Care has therefore to be exercised in reading old records. The draught given was always at the standard displacement and was a light draught never reached on service. After 1936 both the standard and surface displacements in CB 1815 but the draught still applied to the standard displacement only.

12.3 New Construction Policy

10. Up to 1920 the following types of submarines had been discussed, designed and built for the RN:

  • Coastal type, some of which had been fitted to carry mines.
  • Overseas type.
  • Fleet submarines of the K Class.
  • Monitor type submarines of the M Class.

In 1915 the Submarine Committee had thought a cruiser-submarine feasible but no further action had been taken.

11. The first submarine to be laid down in this country after the war was X1, a cruiser submarine design, in the 1921-22 Programme. When completed in 1925 she was the largest submarine in the world. She was not a success and spent most of her time in Dockyard hands until scrapped in 1937.

12.3.1 Minelayers

12. In July 1920 the Naval Staff began an investigation into the ideal requirements for an internal submarine minelayer and DNC prepared a number of designs embodying these requirements. A conference was held at the Admiralty on 22 June 1923 presided over by DTD and attended by RA (S) to decide which of the schemes prepared should be recommended for adoption. The following ideal requirements were agreed upon:

  • (a) Displacement not to exceed 2500 tons submerged.
  • (b) Surface speed as for a patrol submarine of same date.
  • (c) Surface endurance 10 000 miles at cruising speed if possible. In any case not less than 7000 miles.
  • (d) To carry mines and sinkers of non-buoyancy combination type.
  • (e) Mine outfit to be capable of adjustment for depth setting, etc up till time of laying.
  • (f) To have adequate mine embarking arrangements.
  • (g) To be capable of laying in groups of not less than ten mines at 150ft spacing at any speed of vessel from lowest speed to a maximum of 8 knots. No limit laid down for spacing of groups.
  • (h) To be able to lay mines either on surface or submerged.
  • (i) 500 feet diving depth; mine tubes to withstand 200 feet.
  • (j) To have the same W/T arrangements as the patrol submarine.
  • (k) To have Asdics and Echo Sounding.
  • (l) To be suitable for use in tropics.
  • (m) Mines - 40 if possible; not less than 36.
  • (n) Guns - one 4-inch and Lewis guns.
  • (o) Torpedo tubes and torpedoes as for overseas patrol submarines but stern tubes may be omitted if necessary.

It was agreed to recommend that a design with the mining compartment amidships should be prepared with a view to laying down in the financial year 1924/25. This was approved by the board.

13. In January 1924 the then submarine policy was reviewed by RA (S) and concerning submarine minelayers he stated that two types had recently been considered and submitted to Their Lordships:

  • (a) As in Paragraph 12 above for the internal minelayer.
  • (b) A submarine with a large free flooding superstructure in which about 100 mines might perhaps be carried.

He enumerated a few of the material disadvantages associated with type (b) above e.g. the wetting of the mines and subjecting them to diving pressure and also the wetting of the mine transporting gear. If these difficulties could be overcome he considered that type (b) offered a more attractive and efficient means of submarine mine laying than was afforded by type (a).

The Board approved that preliminary discussions with regard to type (b) should be carried on between RA (S) and HMS VERNON. They decided also that the design of an internal minelayer should be proceeded with.

14. In January 1925 RA (S) stated his requirements for a minelayer as 'external mines, bow torpedo tubes only, W/T range of 1500 miles and other features as for the overseas patrol submarine except that the gun armament can be dispensed with.'

The next month a conference was held at the Admiralty to discuss the 1925/26 building programme. Although it was agreed that a minelayer should not be built that year the question of minelayers was discussed. RA (S) registered his opposition to the internal minelayer and mentioned the conversion of an M Class, i.e. a suggestion put up by Captain (S) that M3 should be so converted. The only doubt at the time was whether the then mine would be found suitable for the external type. M3 was eventually converted. The discussions leading up to the conversion of M3 and the satisfactory performance of that vessel eventually resulted in the Porpoise Class minelayers, the first of which was completed in 1933.

12.3.2 Overseas Patrol Type

15. The first post-war design of an overseas patrol submarine to be laid down was Oberon (then called 01) at Chatham in March 1924. The main characteristics were as designed:

Surface displacement 1480 tons
Surface speed 15 knots
Submerged speed 9 knots
Endurance at 15 knots 5000 miles
Endurance economical 12 000 miles
Torpedo tubes, bow Six 21-inch
Torpedo tubes, stern Two 21-inch
Gun One 4-inch
Diving depth 500 feet

16. Late in 1924 the Naval Staff examined the requirements for future submarines and the types to be built in the 1925/26 Programme. The consensus of opinion favoured the overseas type (represented by Oberon then building) and the Staff laid down certain qualities to amplify the Oberon design as follows:

Essential Qualities:

  • 10 000 miles surface endurance and high submerged endurance.
  • W/T range of 1000 miles; 1500 miles if possible.
  • Habitability for the tropics.
  • Quick and deep diving.
  • Inter communication when submerged.
  • Asdics.

Design Qualities:

  • To carry an aeroplane.
  • Gun armament capable of use against aircraft.

It was further suggested that the torpedo armament should be reduced if necessary to enable the essential qualities to be embodied.

17. At the same time the Naval Staff asked Commanders-in-Chief, RA (S) and Captains (S) for their views on the requirements. Many of the views expressed were of course in agreement with the Staff proposals but some of the criticisms and the Staff comments on them are interesting in reflecting opinion at that time. Cost and size of each submarine was of course of great importance. The main criticisms were as follows:

  • (a) 'An endurance equivalent to that of the L Class would be satisfactory'; '11500 miles sufficient since reconnaissance reports which cannot be acted upon at once are of little value'; 'reconnaissance at so great a distance as Japan from Singapore impracticable and not of sufficient value to justify cost.'
  • The Staff comment on these views was that from Hong Kong to the Inland Sea is 1500 miles. The L Class could maintain a 7 days patrol off the entrance to the Inland Sea but would only have 15% of oil fuel in hand as a margin for shadowing, attacking, etc. It may be taken as generally true that as the sphere of operations widens the greater the need for increased endurance and that many unforeseen demands will arise, which can only be fulfilled if the endurance permits of it.
  • (b) On W/T range the views varied from 'long W/T range; 'at least 2000 miles, and 1800 - 1000 miles sufficient'.
  • The Staff remarks were that to obtain 1500 miles range DSD required two 100ft masts 200ft apart and about 200 sq.ft floor space. This would mean an increase of 18 to 20ft in length of submarine and 100 tons in displacement. It was considered undesirable to increase tonnage, which must affect cost, and therefore the numbers that can be made available.
  • (c) On carrying an aircraft a wide range of views resulted. 'An aeroplane is essential. A man-lifting kite would also be useful'; 'provision desirable although the size of the submarine may be increased to a degree, which reduces the number of submarines for which money is available. However they will individually perform more service if carrying an aircraft'; 'aircraft impracticable except for freak submarine, freak aircraft under freak weather conditions.' The Staff stated that no decision could be given until the experiments to be carried out in an M Class submarine have been concluded. It will need a complete redesign and could not be incorporated in existing patrol submarines. This would be a reference to the conversion of M2 into a submersible seaplane carrier.
  • (d) There was general agreement that the chief weapon of the reconnaissance submarine should be the torpedo and some were for as many as possible. Others considered that 'the torpedo armament to be carried to be such as will not impair her value as a scout or increase her size which will lead to reduction in numbers' and 'two or at most four tubes sufficient'. Commenting, the Staff stated that the armament of six 21-inch bow tubes does not interfere with provision of other qualities and meets requirements of those officers who wish for good torpedo armament, without conflicting with the other qualities of those officers who look on it as of secondary importance. They were quite prepared to sacrifice stern tubes to improve habitability.
  • (e) Views regarding the gun armament included 'small and chiefly against aircraft'; 'approximately 6-inch'; 'a single HA gun is of little value, nor is it an essential part of a submarine function to fight aircraft. The gun is for use against weakly armed vessels or patrol craft'. DTD considered one 4-inch gun insufficient whilst DNO proposed one 4-inch or 4.7-inch LA and one 3-inch HA. The Staff comment was that the largest gun which, can be carried without serious loss of submarine qualities, is the 4.7-inch LA.

12.4 Submarine Types

18. A Staff Conference was held in February 1925 and decisions were reached on the necessity for and uses of various types of submarines. The Staff conclusions were discussed at a conference called by DCNS that same month and the following decisions made:

  • 'That the submarine building programme for 1925/26 should be confined to overseas patrol type submarines.' This was confirmed.
  • 'As far as this year's programme was concerned no minelayers should be built but the design for an internal minelayer should be proceeded with.' The first part of this proposal was confirmed and the relative merits of internal and external minelayers discussed. RA (S) was opposed to the internal type owing to the small number of mines (50) carried in a 2500 ton submarine. An M Class, fitted as an external minelayer, would carry at least 80 mines. Also a large economy of internal space would result giving extra W/T range, endurance and habitability. It was decided that RA (S) should forward proposals for further discussion. See Chapter12 Paragraph 14.
  • 'That the building of another cruiser submarine should be postponed until full experience with X1 has been gained.' This was confirmed.
  • 'That economy and the number of overseas patrol types required precluded the possibility of building Fleet submarines at present and that future building of the latter type should await further development of the internal combustion engine.' This was confirmed.

19. At this same DCNS conference some of the controversial items in the Staff Requirements for the new overseas patrol type submarines were discussed as follows:

  • 'Surface speed 17 knots.' This was confirmed as the speed to be obtained with the reserve fuel tanks full. RA (S) pressed for higher speed instancing the American T1-3 (1120 tons, 20 knots) but DNC did not think greater speed could be obtained without increase of size. There were also doubts about the American speed claimed.
  • 'An endurance of 10 000 miles' was confirmed.
  • 'A W/T range of maximum distance obtainable with 50ft masts - a kite aerial being accepted for larger distances.' It was decided to substitute one 60ft mast for two 50ft masts since it was considered that this arrangement would give better results whilst adhering to the principles decided upon by the Staff.
  • 'Two stern torpedo tubes provided their provision does not seriously compromise habitability or seriously hamper the design in other respects.' Their desirability was confirmed but it was decided they should not be included in the design if an extra two knots speed could be obtained by their omission. Model experiments made later at the Admiralty Experiment Works Haslar showed that no gain in speed with the same power could be obtained by omitting the stern tubes and the design therefore proceeded with them.
  • 'Gun armament of one 4-inch or 4.7-inch gun. AA arrangements other than Lewis guns not necessary.' This was confirmed and the 4.7-inch gun considered the most suitable.

From these discussions the Odin Class design started but arguments continued regarding surface speed, stem tubes, habitability and undoubtedly many other items before the design legend and the Board approved drawings for the class on 12 August 1926.

20. In the 5-years Building Programme authorised in 1925, the Admiralty accepted a yearly quota of six submarines and an extended life of twelve years, which had previously been ten years. A total of seventy-two submarines was aimed at, sixty of overseas patrol type and the remaining twelve of -Fleet, mine laying, or other types.

Following this policy six Odin Class, six Parthian Class and six Rainbow Class were ordered in the 1926, 1927 and 1928 Programmes respectively. Two Rainbow Class were subsequently cancelled.

12.4.1 Fleet Types

21. In 1928, the question of the speed required in new construction was brought forward by RA (S) who held that although the designed speed of Odin and Parthian was 17-17.5 knots their operational speed could only be regarded as 15 knots and this speed was not sufficient for submarines which, in an ocean war, should be capable of operating with the Fleet. A new and larger design with an operational speed of 18-19 knots was pressed for, which would enable the submarine to carry out efficiently the functions of a general utility' submarine, including operations with the Fleet for which mobility is essential. C-in-C afloat agreed generally on this point and were most insistent on the need for more surface speed.

The result was the Thames and it was decided that submarines of this type were to be built in future instead of the Odin overseas type.

12.4.2 Coastal Types

22. In 1929, the question of the allocation of a proportion of the building programme to the construction of small submarines was examined. This type was considered necessary for purposes of training, for patrols in the vicinity of our bases and in confined waters in war. The result was the Swordfish.

12.5 Building Programmes

23. Minelayers were again discussed and it was decided that six of this type to carry 50 mines each should be included in future building programmes.

24. The 1929 Programme was originally decided to be two Thames Class and four Swordfish Class, but the London Conference started and a final decision was deferred until the result of the conference was known. The London Treaty was ratified in 1930.

The 1929 Programme was then amended and finally approved in June 1930 as one Fleet submarine (Thames) and two S Class (Swordfish and Sturgeon). The 1930 Programme consisted on one Minelayer (Porpoise) and two S Class (Starfish and Seahorse).

The eventual force envisaged if the policy of building Thames, Porpoise Class and Swordfish Class only was followed would be:

20 THAMES 36000 tons All these tonnages
are at standard
6 PORPOISE 8880 tons
12 SWORDFISH 7800 tons
  52680 tons

The 1931 Programme consisted of one Fleet and the two S Class submarines, the 1932 Programme of one Fleet and two S Class and the 1933 Programme of two Minelayers and one S Class. By this time three Thames Class, three Porpoise Class and nine Swordfish Class had been ordered. The policy then changed. No more Fleet submarines were ordered but the envisaged force of six Minelayers and twelve Swordfish Class was completed in the 1934, 1935 and 1936 Programmes.



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Chapter 11: 1914-18 Saddle Tank Types L and L50 ClassesChapter 13: Cruiser-Submarine X1