Updated 16-Mar-2007

This document is a modern transcription of Admiralty record ADM 1/8586/70. It concerning naval lessons learned from the First World War. It was transcribed by David Chessum on behalf of the the Royal Navy Flag Officers 1904-1945 website. The original file is held at the The National Archives at Kew, London. This Crown Copyrighted material is reproduced here by kind permission of The National Archives.








Para .

Qualities of a battle cruiser


Type stood for speed and gun power


Battle cruisers during the war


Conclusions as to essential characteristics


Gun platform




Report follows terms of reference








Recommendation and remarks




Main armament-


Calibre of gun


Number of guns




Secondary armament


Calibre of gun


Number of guns


Mounting and position


Anti-aircraft armament, star-shell guns and searchlights


Torpedo armament-


General considerations

19, 20

Torpedo armament recommended


Loading requirements


Difficulty of firing torpedoes from submerged tubes at high speed


Above-water torpedo discharges


Gunnery and torpedo control positions and conning tower








Protection necessary to keep ship afloat-


Requirements same as a battleship


Subdivision of propelling machinery compartments

27, 28, 29

Subdivision of boiler rooms


Pumping and flooding arrangements and correction of heel


Protection against above-water attack



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1. Qualities of a Battle Cruiser. – The battle cruiser is a Capital Ship because of her great size and cost: she should, therefore, possess in a greater of less degree the qualities of a battleship. The object of these preliminary remarks is to try and place them in the right order of importance so that the best combination may be obtained.

2. Type stood for Speed and Gun Power. – Since the first battle cruiser was completed, the type has stood for two main characteristics - speed and gun power.

Speed meant the greatest possible, nothing less was sufficient.

Gun power meant an armament which could overwhelm any but contemporary battleships and would not be much inferior to theirs.

3. Battle Cruisers during the War. – We are knowable to judge how our early conception of the battle cruiser type stood the test of war.

The type succeeded admirably in the operations terminating in the battle of the Falkland Islands; no other ships could have succeeded better. Superior speed ensured the enemy being brought to action; overwhelming gun power ensured his destruction.

In the North Sea, both sides possessed battle cruisers and , therefore, their importance to us lay in the means they provided for dealing with their German contemporaries. As events happened, it is impossible to exaggerate the value of these ships during the war. The small area of the North Sea favoured the German policy of raids, as it necessitated their squadrons being in the danger zone only for a short time; to bring them to action, we needed ships would could steam fast enough to intercept them, and to keep up with or overhaul them. Only our battle cruisers could do this. The fear of our battle cruisers undoubtedly prevented the Germans from carrying out raids on a far more extensive scale. The importance of speed and gun power was thus fully confirmed by experience.

4. It was proved in action that our ships were inadequately protected. They lacked the qualities which a Capital Ship must possess to enable her to complete her gunnery function after her speed has brought her into a position to do so; these qualities are protection from gunfire, mine and torpedo. Neither superior speed nor superior gun power, nor both, can take the place of protection; it is useless to build a ship of capital importance which cannot take heavy punishment.

5. Conclusions as to Essential Characteristics. – From the above review of war experience, we arrive at the following conclusions as to the essential characteristics of a battle cruiser:-

Ability to remain afloat, and to float upright, must be as good as the battleship’s

Speed must be as high as possible and should not be less than that of the fastest contemporary battle cruisers. With any lesser speed she cannot accomplish her purpose, which is to bring the enemy battle cruisers to action.

Gun power must be the largest which can be carried on the displacement for a ship of such high speed, otherwise she is an uneconomical unit.

Protection for the vitals from above-water attack must be adequate against the fire of guns of similar calibre to her own.

Endurance must be great because without it operative powers are restricted and, as in the case of weak armament, the ship becomes an uneconomical unit. It cannot be as great as the battleship’s unless displacement is very much increased.

6. Gun Platform. – The battle cruiser must be a good gun platform and possess good manoeuvring qualities whatever her size.

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7. Dimensions. – We recommend that the limits of beam (106 ft.) and draught in the deep load condition (30 ft.) proposed for the battleship should apply also to the battle cruiser, and for the same reasons.

8. Report follows Terms of Reference. – The order in which the main naval requirements of the battle cruiser are dealt with is similar to that in which they are given in our Terms of Reference.


9. We understand that the speed of the new U.S.A. battle cruisers is to be 33¼ knots on a displacement of 43,500 tons, and we recommend that no lesser speed be accepted for our ships.

As in the case of the battleship, the speed required should be obtained in the deep load condition; that is, full sea-going complement and equipment of ammunition and stores, but with only two-thirds fuel on board.


10. We have recommended an official endurance of 6,000 miles at 14 knots for the battleship, and have estimated that she will have to carry 5,250 tons of fuel to obtain this.

The power of the propelling machinery of the battle cruiser being so much greater than of the battleship, her consumption of fuel will necessarily be greater also. “Hood’s” trials not yet being completed, we are unable to use her results as a guide, but we consider than an estimate of 1 ton of fuel for each knot steamed at a speed of about 18 knots is likely to be nearly correct.

We recommend this speed (18 knots) for calculating endurance because battle cruisers may be needed as an advanced or striking force necessitating their being sent ahead of the battle fleet. Also for purely battle cruiser operations involving long passages, the higher the speed maintained, the better the probabilities of success and the more quickly will the operation be completed.

11. Allowing 15 per cent. for fuel, a ship of approximately 40,000 tons displacement can carry 6,000 tons, which, at a consumption of 1 ton per knot steamed, gives an official endurance of 5,100 miles (see para. 15 of Battleship Report).

This distance we consider the minimum necessary and would much prefer to increase it to 6,000 miles, but we don not wish to force up size and cost solely on account of endurance, which is of less importance than speed and gun power.




12. Calibre of Gun. – The arguments respecting calibre of gun for the battleship apply equally to the battle cruiser; all contemporary capital ships should be armed with the same gun.

13. Number of Guns. – Weight and space needed for propelling machinery and boilers have hitherto precluded battle cruiser receiving an armament equal to that of contemporary battleships and, as speed comes before gun power, we consider that this must be accepted again in new designs. Even then the battle cruiser will be the larger vessel.

In para. 41 of the battleship report we recommended that, for fire control reasons, a minimum of eight guns should be carried.

More than four turrets are out of the question unless size of ship be exaggerated undesirably.

14. Recommendation. – We recommend that the battle cruiser should carry eight guns of the same calibre as the battleship, mounted in four turrets, the armament being thus well distributed. Also, we do not advise a less number of turrets than in new foreign ships.

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15. Calibre of Gun. – The secondary armament of the battle cruiser should consist of guns of the same calibre as in the battleship.

All the arguments we gave in favour of a gun firing a 100-lb. shell apply in full.

16. Number of Guns. – We consider that the minimum is six guns aside, and do not press for a larger number in order that weight may be saved in this as in other secondary characteristics.

17. Mounting and Position. – The guns should be mounted in pair-gun turrets, on two deck levels, as in the battleship, the centre turret being able to fire over the other two.



18. Requirements for the above are the same for the battle cruiser as for the battleship.



19. Battle cruisers should be designed to meet contemporary foreign battle cruisers, and against these ships the gun and not the torpedo is the important weapon. On these grounds there is, therefore, no reason to exceed the torpedo armament of one submerged tube each side considered necessary for the battleship. (See paras. 87 to 91 of Battleship Report.)

20. If battle cruisers engage battleships, no increase of torpedo armament can compensate for their inferiority in gun power and protection; but since opportunity for torpedo fire depends upon position, and position depends primarily upon speed, battle cruisers may find themselves favourable placed for torpedo fire against battleships.

It is, therefore, advantageous to provide them with a torpedo armament for use against the enemy Battle Fleet.

21. Torpedo Armament Recommended. – If design admits, we recommend two submerged torpedo tubes each side in separate compartments, and an outfit of not less than six torpedoes per tube.

22. Loading Requirements. – The arrangements for loading should be such that half the torpedoes at each tube on the engaged side can be fired in quick succession, and that the remainder can be got ready quickly for a second series.

A rate of fire of one torpedo per tube per minute in each series should be possible; the interval between series should not exceed five minutes.

23. Difficulty of Firing Torpedoes from Submerged Tubes at High Speed. – The recommendations in paras. 21 and 22 hold good whether or not difficulties occur in firing torpedoes at the highest speeds. Ships will not always require to be steamed at full speed in action and it would be unwise to give up an offensive weapon because of limitation which are not vital and may be overcome. Further, if battle cruisers are free to manoeuvre to attack with torpedoes, they can afford to reduce speed when in position for firing.

24. Above-water Torpedo Discharges. – We are opposed to above-water torpedo discharges being placed in battle cruisers.

During the war, and more especially after Jutland, demands arose for more torpedoes in our fastest Capital Ships, light cruisers and destroyers. This led to the adoption of above-water tubes in heavy ships, such as those of the “Repulse” and “Courageous” classes, and we have evidence in favour of constructing special torpedo carriers.

Undoubtedly, the above-water tube is an admirable arrangement in small vessels such as light cruisers and destroyers as it takes up little room, is not unduly heavy and gives them a weapon which they otherwise could not possess for attacking heavy ships. The risk incurred in their carrying torpedoes above water can be

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accepted; it is not inconsistent with design. On the other hand, in armoured ships, most thorough precautions are being taken to safeguard magazines, which are far better protected than any above-water torpedo tube can be, and we think it would be very illogical to install a new source of danger.

We consider, therefore, that the risk should not be taken in Capital Ships, which have their own definite functions to perform and ought not to be encumbered with weapons which are not a primary form of offensive power to them. We find no evidence to show that, on war experience, more torpedoes are needed in battle cruisers.


25. Requirements for the above are the same for the battle cruiser as for the battleship.


26. The requirements of a battle cruiser are the same as for a battleship, except where design must differ in order to accommodate extra machinery and boilers.


27. Sub-division of Propelling Machinery Compartments. – We do not think it practicable to adopt a three-shaft design of propelling machinery in a battle cruiser on account of the very high power that would have to be carried by each shaft. A four-shaft design is therefore recommended.

28. We consider that the arrangement adopted in “Hood” of installing the machinery in three compartments, each extending across the ship and each containing one or two complete sets, is a distinct advance on previous practice and is the best to adopt for the new battle cruisers.


29. We are not satisfied, however, that the torpedo protection of “Hood’s” engine room is adequate, as the protective bulkhead, which is of 1½-in. steel, is only10 ft. from the side and is not even thickened to compensate for the lack of the additional three-quarter inch bulkhead which covers the boiler room and magazines, nor is there any interior watertight bulkhead abreast the forward engine room.

The torpedo bulkhead should be not less than 13 ft. from the side and not less than 2 in. thick; between it and the large interior compartments there should be a watertight bulkhead not less than 17 ft. from the side. (See para. 124 of the Battleship Report.). If these distances cannot be obtained by placing the shafts closer to one another, then we recommend that trials be carried out to ascertain whether the same security can be given by a thicker protective bulkhead more strongly supported.


30. Subdivision of Boiler Rooms. – We recommend longitudinal subdivision of the main watertight sections containing the boilers into thirds, as in the battleship.


31. Pumping and Flooding Arrangements and Correction of Heel. – The requirements of a battle cruiser are the same as a battleship’s.




32. The protection necessary for the vitals of a battle cruiser is the same as for a battleship, because she is required to withstand attack from the same calibre of gun, but the area to be protected is larger.

It is obvious, therefore, that protection must be either differently arranged or reduced.

There is no difference between the vitals of a battleship and a battle cruiser; they consist of magazines, main armament redoubts and gun positions, and motive power. We have already endeavoured to rearrange battleship armour in order to concentrate it where it is most needed, and if a more economical disposition had been considered efficient we should have proposed it.

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We consider, therefore, that the principles governing the protection of battleships should be adhered to for battle cruisers, and that weight must be saved by reduction in thickness all round.

We recommend reductions varying from 10 to 20 per cent., according to position of armour; over magazines and on main armament redoubts and gun positions it should not exceed 10 per cent., over engine rooms and on the belt 15 per cent., over boiler rooms, 20 per cent.


33. We are not in a position to make nay definite recommendations on displacement, because it depends on the qualities of speed, endurance, armament and protection, which we have recommended should be embodied in the design.

It is useless to have a ship which is too weak or too slow; it is unwise to have a ship which is unnecessarily large as a target, costly to build, and difficult to berth and handle. “Hood’s” length and displacement seem excessive, and it would certainly be desirable to reduce them.


34. Our recommendations in respect to special fittings and equipment of the battleship apply in general to the battle cruisers and there are no special points to which we wish to draw attention.