British Fiji Class Cruisers and their Derivatives

Chapter 1

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CLASS ORIGINS

BRITISH CRUISER POLICY

The Fiji class cruisers trace their origins to the Second London Naval Treaty of 1936 and the process of rearmament that immediately preceded the Second World War. The treaty proved to be a failed agreement that quickly collapsed in the face of Japan’s withdrawal from the system of naval armament limitation and ever-growing international tensions. Nevertheless, it had a huge influence on many of the most modern warship designs that were to fight in the imminent conflict. From a British perspective, one of its most profound results was to allow the Royal Navy to build the type of cruisers it desired in the numbers it required after a prolonged period when it had consistently failed to achieve these objectives.

Cruisers were fundamental to British naval policy in the period between the two World Wars. Their importance derived from the Royal Navy’s paramount responsibility of safeguarding the seaborne trade routes upon which the British Empire’s prosperity and security depended. Although the First World War had revealed the profound vulnerability of merchant shipping to the new danger of submarine warfare, the protection of trade was still essentially regarded as a cruiser role in the interwar years.¹ A particular concern was the rapid expansion of Japan’s naval power and its ability to interdict Britain’s crucial trade routes in the Far East. It had been relatively easy to contain the German Imperial Navy’s surface fleet given the Royal Navy’s control of the exit routes from the confined waters of the North Sea. The same option could not be so readily deployed against Japan.

It was these considerations that determined British cruiser policy over much of the interwar period. By 1923, the Admiralty had concluded that at least seventy cruisers would be needed to provide the necessary level of security. The calculations behind this number were to vary over time but the most enduring formula appears to have been based on a need to maintain twenty-five cruisers with the fleet to match likely Japanese strength in the main theatre of war, with the balance deployed for trade protection. The seventy-strong cruiser force remained a critical Admiralty objective throughout the interwar period until revised upwards in the late 1930s as a global naval war against multiple enemies became increasingly likely. It was also to become a key influence on the Fiji class’s acquisition.

Bermuda is seen with Glasgow whilst operating as part of the First Cruiser Squadron in the Mediterranean Fleet during 1954. Cruisers were fundamental to British naval policy for much of the twentieth century, particularly in the period between the two World Wars. The Fijis resulted from ongoing efforts to secure sufficient numbers at an affordable cost. (Author’s collection)

The ‘County’ class cruiser Berwick, part of the initial Kent class batch, pictured on the River Clyde during the course of sea trials. The photograph was taken before the design’s funnels were raised to prevent smoke interfering with crucial control positions. Armed with eight 8in guns and providing good endurance, the ‘County’ class were built to the parameters established by the Washington Naval Treaty of 1922. Although well suited to protecting the British Empire’s all-important trade routes, they proved too expensive to be built in the numbers required. (Author’s collection)

Although the need for seventy cruisers was to remain an enduring Admiralty requirement, it was also one that proved remarkably difficult to achieve in practice. The obsolescence of much of the cruiser force after the First World War meant that a large and costly programme of new cruiser construction – by far the largest individual element of future Royal Navy procurement – would be required to meet the targeted number. However, British government finances had been stretched to breaking point by the demands of the Great War and a period of defence austerity was required for financial stability to be achieved. The infamous ‘Ten Year Rule’ of October 1919, mandating that the armed forces should base their planning on the assumption that the British Empire would not be involved in a major conflict for the next decade, paved the way for a substantial decline in the naval budget. Even with capital-ship construction largely suspended by the Washington Naval Treaty, there was simply insufficient money to fund a cruiser programme of the size the Admiralty envisaged.

NAVAL LIMITATION – WASHINGTON & LONDON

Signed on 6 February 1922, the Washington Naval Treaty had the somewhat paradoxical effect of exacerbating the Admiralty’s cruiser problem.² Intended to prevent a new naval arms race of the type that had preceded the First World War, its main successes were to reduce the number of capital ships in service with signatory navies and place quantitative and qualitative restrictions on their future construction. Cruisers and smaller vessels were not limited by number but were made subject to qualitative limits that restricted their armament to 8in (203mm) calibre and their displacement to 10,000 tons. The latter figure was based on a new definition of displacement – ‘standard’ displacement – that was mandated under the treaty to ensure consistency in international comparisons. Perhaps inevitably, something of a new international contest in building so-called ‘treaty cruisers’ up to the maximum limits allowed by the agreement rapidly developed. The resulting ships – the Royal Navy’s initial entry into this competition was the famous ‘County’ class – were well suited to guarding the trade routes but came at a high price. Various economies, including construction of the smaller York and Exeter, were attempted. However, by 1928, cruiser policy was in disarray as it became apparent that the seventy-strong fleet could not be afforded on the basis of existing designs.

The Royal Navy and its political masters sought a way out of the impasse. An attractive option was the renewed construction of smaller, cheaper cruisers armed with lighter 6in (152mm) guns closer in displacement to those built immediately prior to and during the Great War. These ships would have the agility to fulfil the fleet role but – if built with sufficient range – could also police the trade routes in a more economical fashion. There was one major hurdle. Unless other treaty signatories could be persuaded to abandon the larger, 8in type, the Royal Navy’s smaller cruisers would be at a disadvantage in any encounter with their foreign counterparts. Unfortunately, British requirements ran contrary to those of the United States and Japan, which favoured larger cruisers to scout the vast expanses of the Pacific. Moreover, the Americans were not prepared to accept anything less than parity (measured by tonnage) with the Royal Navy and – without a global empire to protect – wanted to achieve this through reductions in British cruiser strength. Needless to say, it proved difficult to resolve these conflicting desires. However, pressures on the global economy after the 1929 Wall Street Crash and the influence of new political leaders in Britain and the United States allowed a compromise to be hammered out. The result was the London Naval Treaty of 1930.

Equipped with eight 6in guns, Leander was ordered as the prototype of a new class of light cruiser in an attempt to persuade other leading navies to adopt the smaller cruisers that the Royal Navy wanted to build to meet its numerical requirements. Although a new naval limitation agreement – the London Naval Treaty of 1930 – was successfully concluded, it did not produce the outcomes that Britain desired. This photograph was taken in July 1933, soon after the ship’s completion. (Author’s collection)

Building on the foundations laid at Washington, the new treaty maintained previous limitations on capital ship construction for a further five years and extended quantitative limits to other warship types.³ The complex provisions relating to cruisers sought to balance conflicting American, British and Japanese requirements. Royal Navy objectives were met by splitting cruisers into two categories dependent on whether they were armed with (i) guns exceeding 6.1in (155mm) calibre or (ii) equipped with guns of 6.1in calibre or less; subsequently often referred to as ‘heavy’ and ‘light’ cruisers. Signatories were limited as to the total tonnage of cruisers they could have in either category as of 31 December 1936. They also faced numerical restrictions as to the number of heavy cruisers they were permitted. In return, Britain accepted that its total cruiser force should total no more than 339,000 tons on a standard displacement basis, effectively forcing a reduction in its cruiser ambitions from seventy to fifty ships. It was also restricted in the tonnage of new cruisers it could build over the life of the treaty. The force reduction was essentially politically driven by the then Prime Minister, Ramsay MacDonald, to reach a consensus with the United States. This was only reluctantly accepted by the Admiralty as a temporary constraint for the life of the treaty.⁴

The figures agreed for British total cruiser and new construction tonnage were calculated on the basis that future orders would largely be concentrated on a new 6,500-ton light cruiser type.⁵ A prototype of this design – Leander – armed with eight 6in guns had been ordered before the treaty was signed in an attempt to influence its outcomes. However, the only constraint on the displacement of individual cruisers was the 10,000-ton Washington Treaty limit. As the Pacific-orientated fleets of Japan and the United States remained wedded to the concept of larger ships, they started to order light cruisers towards the upper end of this restriction. The result was the emergence of large light cruisers armed with as many as fifteen 6in or 6.1in guns that comprehensively outclassed the British Leanders. Eventually the Admiralty were forced to follow suit, commencing design work on what as to become the ‘Town’ or Southampton class in the summer of 1933. Displacing slightly over 9,000 tons in their original iteration and armed with twelve 6in guns, they were to prove well-balanced ships that gave excellent wartime service. Nonetheless, their construction had two short-term consequences. One was that their increased displacement meant that there would be insufficient treaty tonnage available to achieve the planned fifty-cruiser strength, holding out the prospect of a temporary dip in force structure. The other was a rebound in cruiser construction costs to a figure approaching that of the previously unaffordable ‘County’ class.⁶

REARMAMENT & THE SECOND LONDON NAVAL TREATY (1936)

To a large extent, these two concerns were overtaken by events as the assumptions of lasting peace made in the after-math of the First World War started to crumble in the face of international political developments. The start of the shift in the global security situation can be traced to September 1931, when elements of Japan’s Imperial Army invaded the Chinese region of Manchuria. Manchuria’s swift annexation – viewed with both approbation and alarm by the British government – and the ‘Shanghai Incident’ of January 1932 were key factors behind the Cabinet’s decision to terminate the ‘Ten Year Rule’ in March of that year. The growing possibility of all-out war in the Far East was followed by Hitler’s rise to power in Germany in early 1933 and the subsequent acceleration of German rearmament. This effectively gave rise to the risk of naval war in more than one theatre, a danger further exacerbated by Italy’s increasingly expansionist ambitions best demonstrated by its invasion of Ethiopia in October 1935. Slowly at first but with a steadily-increasing momentum, Britain began to rearm to face a new global war.

The ‘Town’ class cruiser Glasgow is pictured in Portland Harbour with Weymouth in the background in this late 1930s view. The ‘Towns’, armed with twelve 6in guns, were built as a response to large American and Japanese 6in cruisers. Although a successful design, they were larger than was considered optimal for Royal Navy requirements and pushed costs close to those of the unaffordable ‘Counties’. (Author’s collection)

Amongst the first steps taken towards re-establishing British military readiness was the creation of the so-called Defence Requirements Sub-Committee (DRC) of the Committee of Imperial Defence in November 1933. This was tasked with developing proposals to make good the most significant defence deficiencies within a period of five years. The ongoing constraints of the London Treaty on new construction meant that the committee’s naval focus was initially on increasing reserves of items such as ammunition, fuel and stores, as well as the modernisation of existing ships and base infrastructure. Comments on the future shipbuilding programme were limited to sketch estimates of its likely cost over a five-year period on the basis of existing London Treaty limitations. Even so, when the proposals in the DRC’s first report were considered at a political level in mid-1934 it was determined, given the growing threat from Germany and continued financial constraints, to prioritise the Royal Air Force’s needs at the expense of those of the other armed services. Whilst this was to prove to be only a temporary setback, it did serve to illustrate the challenges facing any major programme of naval expansion, including growth in the cruiser force.

It was against this backdrop that preparations commenced for the new naval conference that would be required to replace the existing treaty regime. These commenced early in 1934 when the navy’s professional head, Chief of the Naval Staff (CNS) and First Sea Lord Ernle Chatfield, approved a memorandum setting out the Admiralty’s objectives for the forthcoming discussions. From an overall strategic perspective, the memorandum reviewed the comparative decline in British naval power since the Washington Treaty in the context of the evolving risk the Royal Navy could be involved in simultaneous conflicts in Europe and the Far East. It concluded that the aim should be a revised ‘one power standard’ – explicitly excluding the possibility of war with America – under which:

A major British objective in the negotiations that secured the Second London Naval Treaty was to persuade the US Government to halt the construction of large cruisers, represented in this photograph of Vincennes (CA-34), the final member of the New Orleans class. American acceptance that they had ordered sufficient large cruisers to meet their immediate requirements meant that a compromise could be reached, resulting in the qualitative 8,000-ton standard displacement and 6.1in calibre armament restrictions on which the Fijis were based. (US Navy History & Heritage Command NH 50844)

We should be able to send to the Far East a Fleet sufficient to ‘cover’ against the Japanese Fleet; we should have sufficient additional forces behind this shield for the protection of our territories and mercantile marine against Japanese attack; at the same time we should be able to retain in European waters a force sufficient to act as a deterrent to prevent the strongest European Naval Power from obtaining control of our vital home terminal areas while we can make the necessary redispositions.

⁷

Based on this revised standard, it was, perhaps, inevitable that the First Sea Lord’s memorandum called for the previously targeted cruiser force of seventy vessels to be reinstated. As had been acknowledged at various times since this objective had first been established, it was agreed that ten of these ships could be over-age.⁸ This was by no means a modest request given that cruiser expansion would have to take place alongside replacement of the now life-expired battle fleet. Consequently, there was a renewed push to reduce individual ship costs by seeking further international constraints on qualitative characteristics. Specifically, the First Sea Lord stated that objectives from the future treaty negotiations should be:

a. A prohibition on further construction of 8in heavy cruisers.

b. Construction of large 6in light cruisers should be based on the Washington Treaty ratio for battleships. The British Commonwealth and United States would be restricted to ten each, with Japan limited to six.

c. A qualitative restriction on future 6in light cruisers to 7,000 tons and 6.1in guns (although 7,500 tons would be acceptable).

d. A British tonnage figure for forty-five ships of the qualitative limit agreed for cruisers described in category c. above (i.e. which when combined with fifteen existing 8in cruisers and ten large 6in cruisers would achieve the desired total of seventy). Moreover, Japan should only be allowed 50 per cent of thus tonnage and France only 50 per cent of total British light cruiser tonnage (i.e. categories b. and c. combined).

e. Acceptance that no quantitative limits on future light cruiser construction could be agreed should a., b. and c. above be achieved.

It is interesting to note that – even with these more stringent qualitative limitations in place – the tonnage required for the desired British cruiser force would be significant, increasing from the 339,000 tons agreed in 1930 to just under 562,000 tons. This reflected both the return in the number of cruisers sought to seventy and the fact that the small First World War-built light cruisers would be replaced by larger ships better suited for longer-range deployment.

Many of the details of these initial proposals were subject to revision during the extensive discussions that took place both before and during the Second London Naval Conference that was convened in late 1935 in a bid to extend the treaty regime.⁹ Importantly, however, the Admiralty was to achieve broad political acceptance from within the British political establishment of the necessity of returning to the objective of a seventy-strong cruiser force. It was agreed that this would form the basis for British conference proposals and it also fed into the DRC’s ongoing deliberations on the broader rearmament programme. In early March 1936, the annual Statement Relating To Defence to the House of Commons made specific reference to the aim of increasing the number of cruisers to seventy, of which ten would be over-age.¹⁰

The final act in the political process that would result in the Fiji class occurred on 25 March 1936 with the signature of the Second London Naval Treaty by the British Commonwealth, France and the United States. Japan had previously withdrawn from treaty negotiations over refusal of her demands for naval parity whilst Italy decided to withhold its approval as a result of ongoing fallout from her invasion of Ethiopia.¹¹ The treaty’s scope was further reduced by failure to reach consensus on an extension of any quantitative restrictions. Its main achievements were expanded requirements around the advanced notification of new construction programmes and agreement of new qualitative limitations. Understandably, the United States had initially reacted with alarm to the desired British increase in cruiser numbers. It also remained wedded to the large cruiser concept. However, a strong desire to secure a further agreement and a seeming acceptance that the US Navy had ordered sufficient large cruisers to meet its immediate requirements meant that there was room for compromise. The treaty determined that no cruisers armed with guns of more than 6.1in calibre of a displacement over 8,000 tons should be constructed until the agreement’s expiry at the end of 1942. With political support secured and the quantitative constraints of the First London Naval Treaty soon to be removed, the Royal Navy could finally look towards achieving the cruiser force it had sought for so long to obtain.¹²

INITIAL DESIGN WORK FOR THE 8,000-TON CRUISER

Preliminary design work on what was initially referred to as the 8,000-ton cruiser began whilst the Second London Naval Conference was still underway. The design formed part of a much larger programme of naval construction that would follow the easing of treaty restrictions and reflected the deteriorating international environment. The cruiser element of this programme had two main components that mirrored the two primary roles of Royal Navy cruisers of this period. Fleet cruisers were optimised for reconnaissance and screening duties in conditions of poor visibility, as well as supplementing the fleet’s anti-aircraft defences. A low silhouette and agility were key design considerations, mandating construction to the minimum practical size. This role was to be met by the c. 5,500-ton Dido class, which were intended to replace their First World War predecessors of the ‘C’ and ‘D’ classes. The other, all-important trade protection mission demanded a larger ship with the seakeeping qualities and high endurance required for prolonged detached operation and which would be sufficiently powerful to prevail against any enemy raider that was likely to be encountered. Although also required to serve with the fleet if necessary and sometimes referred to as a general purpose design, the 8,000-ton cruiser was optimised to perform the trade route role. These new ships could expect to meet heavy 8in-armed cruisers and larger 6in cruisers that predated the 1936 treaty’s qualitative restrictions. Moreover, as Japan had not signed the new agreement, the nature of the future cruisers she might build was uncertain. Given this, the Admiralty’s only practical option was to design the most powerful cruiser it could within the new treaty limitations, at least until more about foreign building policy became known.

The formal design process was governed by a ‘Procedure to be adopted in the preparation of Designs of H. M. Ships’ that had been approved by Admiralty Board Minute No 3169 of 15 February 1934.¹³ The procedure tasked the Assistant Chief of the Naval Staff (ACNS) with commencing the process by overseeing the preparation of staff requirements that would form the basis for drawing up one or more sketch designs for any new ship. These staff requirements would be written in consultation with other relevant Admiralty departments. They were to encompass particulars relating to armament, seaworthiness, endurance, speed, protection, aircraft equipment, communications, habitability, silhouette and any special feature of equipment required and any limitation on displacement or dimensions. Consideration had to be given to foreign shipbuilding developments and naval treaty limitations. The resulting draft would then be discussed at a meeting comprising the First Sea Lord/CNS, Deputy Chief of the Naval Staff (DCNS), ACNS and the Third Sea Lord or ‘Controller.’ The Controller was in charge of the navy’s materiel and was responsible for instructing the Director of Naval Construction (DNC) – the Admiralty’s principal technical adviser on warship design and head of its design department – to prepare sketches based on the requirements finalised at this meeting.

As is often the case in life, actual practice often differed from the written procedure. In particular, the Controller would often request the production of preliminary sketches before work on the staff requirements commenced and – in a reversal of the formal process – it seems that these sometimes informed the scope of the requirements. In the case of the 8,000-ton cruiser, it is apparent that preliminary design commenced as early as January 1936 whilst the staff requirements were not finalised until around June of that year. It is possible that this apparent subversion of the written procedure could have been influenced by the desire of a forceful Controller to stamp his mark on the design process. The Controller at the time the Fiji class was designed – the then Vice Admiral, Sir Reginald G H Henderson – certainly fits this description.¹⁴

Responsibility for overseeing production of the sketch designs was in the hands of the then DNC, Sir Arthur W Johns.¹⁵ A sick man in 1936, his deteriorating health would force his retirement before the Fiji class’s design was completed. The actual task was assigned to the directorate’s cruiser section, which is believed to have been headed by Sidney E Boyland at the time. Much of the actual preliminary design work was carried out by Constructor E G Kennett, who had also taken lead responsibility for many of the Royal Navy’s preceding cruiser designs.¹⁶ J L Bessant, an assistant constructor working with Kennett, as well as C S Lillicrap – a senior constructor and recognised cruiser expert who became the Head of the Cruiser Section in 1938 and eventually rose to be DNC – also played a role in the process, the latter only peripherally.

Lack of surviving documentation means that tracing the early stages of the 8,000-ton cruiser’s development is not easy. In particular, Constructor Kennett’s notebooks have not survived, meaning that much of the work on the early sketch designs – and the factors that influenced them – has been lost. However, there is sufficient information to show that this early work essentially followed two main strands. One, rather obvious, approach was to take the existing ‘Town’ class cruiser design and progressively scale it down to meet the 8,000-ton limit. The first evidence of this strand is contained in Assistant Constructor Bessant’s workbook on 23 January 1936, when DNC asked him to calculate the displacement of a ten-gun 6in cruiser (‘A’ and ‘Y’ turrets being twins and ‘B’ and ‘X’ triples) with other characteristics identical to the 1935 programme ‘Towns’.¹⁷ The resulting design – labelled K21 or ‘P’ – came out at c. 8,900 tons compared with the 9,400-ton Liverpool used as a baseline. An alternative K22 (‘Q’) based on Liverpool but with three triple turrets displaced 8,500 tons. Bessant was then asked to reduce both these designs to 8,000 tons. The nine-gun ship was labelled K23 (‘R’) and the ten-gun ship K21 modified (‘S’). In early February, Bessant also undertook some work exploring weight reduction options for an existing 8,500-ton twelve-gun 6in cruiser sketch armed with three quadruple turrets. These were of a type designed for but not ultimately used in Belfast and Edinburgh, the final, 10,000-ton iteration of the ‘Town’ class. It has been speculated that the original 8,500-ton quad-turreted ship might have been K20 in the series but K24 seems at least equally likely. Characteristics of these early designs are summarised in Table 1.1.¹⁸

These photographs of the ‘Town’ class cruiser Liverpool, which was initially ordered as one of the 1935 programme variants of the type, were taken off Malta in January 1952. By this time she was armed with nine 6in guns in three triple turrets, ‘X’ turret having been removed by way of weight compensation during the Second World War. Two of the original 8,000-ton cruiser sketches produced by Assistant Constructor Joseph Lancelot Bessant – labelled K22 and K23 – were based on three triple turret-armed variants of Liverpool and, accordingly, would have been very similar to these photographs if adopted. (ADM 10938/10942)

The other approach was based on use of the new twin 5.25in dual-purpose (DP) mounting then being adopted in the King George V class battleships and Dido class cruisers. It appears to have been driven by Controller Henderson. Compared with previous light cruiser designs – that used 6in guns for their main surface armament and 4in weapons as the primary means of anti-aircraft defence – a unified 5.25in armament offered two main advantages. Not only would it improve anti-aircraft capacity, not least by putting the anti-aircraft armament under armour, but it would also be more efficient to man than a design with separate low-angle (LA) and high-angle (HA) guns. In mid-February 1936, the Controller asked Senior Constructor Lillicrap to investigate how many 5.25in turrets could be carried in an 8,000-ton ship, with Lillicrap also using the expedient of scaling down a ‘Town’ class cruiser as his starting point. His rough calculations suggested that there would be insufficient weight to provide a satisfactory armament if other design characteristics remained unchanged but this was not to be the end of the matter.¹⁹

As preliminary design work continued through the spring of 1936, lengthy discussions were held to finalise the formal staff requirements for the new ships. These were summarised in TD Memo No 143 of June 1936. Whilst, unfortunately, this is another document that is not traceable in the archives, its key points were noted in a later document, as set out in Table 1.2.²⁰ These essentially continued the process of scaling down the ‘Town’ class design to meet the new displacement limit. More specifically, protection was to be in line with Belfast and Edinburgh – the most heavily armoured ‘Town’ class variants – but reductions were accepted both in the scale of armament and maximum speed. The 6in gun was preferred over the 5.25in, with the benefits of the latter’s anti-aircraft capabilities being regarded as an unwelcome concession to defence at the expense of offence. An interesting requirement was that for twelve torpedoes in four triple tubes; a seeming nod to the design’s secondary fleet role given that torpedoes were more highly valued in this environment.

SKETCH DESIGN PROPOSALS & THEIR CONSIDERATION

The agreement of staff requirements appears to have cleared the way for the DNC to put forward a number of sketch designs to the Controller for formal consideration. Although the requirements might seem to have put paid to the use of a 5.25in armament, this was not the case. Doubtless due to Controller Henderson’s influence, preliminary design work on both these and ships armed with 6in guns continued in parallel.²¹

TABLE 1.2: SUMMARY STAFF REQUIREMENTS FOR THE 8,000-TON CRUISERS OF THE 1937 PROGRAMME

Note:

¹. Details from ADM 1/24224.

Note: The drawings for K23A and K26 are based on those submitted to the Controller on 9 July 1936 and contained in ADM 1/9402. No drawing was produced for K23B due to its similar appearance to K23A. The drawing reproduced here has been created on an indicative basis from written data contained in the submission.

The first submission was made on 9 July 1936 when the Deputy DNC, F Bryant, put forward three 6in-armed designs on behalf of the now-absent DNC. These were later to be followed by two additional outline 6in designs on 16 September 1936, these under the signature of the new DNC, Stanley V Goodall. These designs are considered together in Table 1.3. The first three sketches – labelled K23A, K23B and K26 – were all ships with three triple turrets derived from Assistant Constructor Bessant’s earlier work on K23. K23A had a broadly similar arrangement to the 1933–7 programme ‘Towns’ but with one less turret and a reduction in armoured protection to a scale roughly equivalent of the earlier Leander. K23B was a shorter, slower design with less powerful machinery to achieve broadly the same level of protection found in Belfast and Edinburgh. Both had a secondary armament of four twin 4in HA mountings. K26 had the same length and armour as K23B but omitted aircraft arrangements in favour of an enhanced anti-aircraft armament of six twin 4in HA mounts and slightly more powerful machinery. It utilised an arrangement that placed the 4in magazine between the forward engine room and aft boiler room, shortening the route of the ammunition supply. This would ultimately be adopted – in modified form – in the final ships. The two later designs – K27 and K28 – both incorporated a revised protection scheme falling between K23A and K23B/26 but with full armour belts in place of the internal forward and aft ‘boxes’ covering the magazines and shell rooms of the earlier trio.²² Both retained full aircraft arrangements and incorporated greater firepower. K27 used the new quadruple 6in turret designed for Belfast and Edinburgh. Three mountings were carried for a total of twelve guns. K28 adopted a mixture of triple and twin turrets similar to Bessant’s K21 and K21 modified – but with ‘A’ and ‘Y’ mountings being the triple turrets – for a total of ten 6in guns. Both these designs had to sacrifice machinery weight and, hence, speed to carry the upgraded armament, particularly the longer, four-turreted K28.

Note: The drawings for K27 and K28 were submitted to the Controller on 16 September 1936. Along with the previously-submitted K23A, 23B and K26, these were the 6in-gun cruiser designs that he considered in mid-September prior to drawng up a shortlist of 8,000-ton cruiser sketches for presentation to the Sea Lords.

The initial six 5.25in sketch designs were submitted on 23 July 1936 under the designations K25A to K25F, with Stanley Goodall signing on behalf of the DNC (his appointment to the role of DNC was announced two days later). They were later followed by two additional outline designs, labelled K25G and K25H. As was the case for the additional 6in sketches, these were submitted on 16 September. All these designs are summarised in Table 1.4. The base design, K25A, incorporated seven twin 5.25in turrets with four mountings forward and three aft. The forward mountings had an unusual arrangement under which two mountings were located side-by-side in ‘B’ position, thus giving three levels of armament in both the forward and aft groups. Sufficient machinery weight was provided to achieve 32.5 knots but protection was less than for any of the 6in-armed ships. It utilised the mixed armoured belt and box arrangements of the early 6in design trio. Sketches K25B through to K25D provided various alternative improved armour arrangements based on the K25A configuration at the expense of half a knot in speed, whilst K25E surrendered an additional knot for a further strengthening in armour. Along with K25B, it substituted a complete armoured belt for the combined belt and box of the other July submissions. K25F had the same, minimal armour scheme as K25A but saw machinery weight reduced to that required for 31.7 knots to accommodate an additional, eighth twin turret aft in an arrangement that mirrored that of the forward armament group. The later K25G was produced as an outline sketch to illustrate an alternative configuration for K25A through to K25E under which the four forward mountings were all superimposed on the centreline. K25H was another variant of the K25A sketch to illustrate a scheme of protection similar to that in Belfast and Edinburgh (and thus broadly equivalent to the 6in-armed K26) at the cost of a fall in speed to 29 knots.²³

With no fewer than thirteen alternative designs now submitted for his consideration, the Controller was almost ready to select a shortlist of options for formal Admiralty consideration. However, before requesting a meeting with Admiralty colleagues to discuss the proposals, he asked the DNC to produce a further iteration of the K23 series. This was K23A*. The sketch was a more heavily armoured variant of the previous K23A first put forward in July. It replaced the mixed belt and box arrangement of K23 with a full armoured belt that increased side armour to 3½in and deck armour to 2in. At the same time, the illustrative K25G outline was refined on the basis of the armour scheme drafted for K25E to provide an equivalent level of protection. This work was complete by 18 September; only two days after the preceding sketches had been submitted.

THE 8,000-TON CRUISER DESIGN IS AGREED

Now satisfied that everything possible had been done to squeeze the maximum potential out of the 8,000-ton limit, the Controller requested a Sea Lords’ Meeting to discuss the new design. This was held on Monday, 28 September 1936.²⁴ Although the ‘Procedure to be adopted in the preparation of Designs of H. M. Ships’ stated that consideration of the sketches was normally the responsibility of the First Sea Lord, ACNS and Controller, it appears that the Second Sea Lord (Chief of Naval Personnel), Fourth Sea Lord (Chief of Naval Supplies and Transport) and DCNS were also involved in these discussions.²⁵

The Controller put forward three designs for consideration: K23A*, K25G and K27. These are summarised in Table 1.5. By virtue of the revisions that had already been carried out, all had broadly similar protection focused on a main belt with 3½in side and 2in deck armour. Although the side armour was thinner than the 4½in protection fitted to the ‘Towns’, it was considered to be sufficient to resist 6in shell hits at most practical ranges. K23A* and K25G were both capable of 31 knots, whilst K27 was a knot slower. The main choice therefore essentially came down to armament. K23A* carried three triple Mk XXIII 6in mountings using the long-trunk arrangement introduced in Belfast and Edinburgh, supplemented by four HA twin Mk XIX 4in mountings. K27 had three of the new quadruple 6in mountings initially conceived for the Belfast class, again with four twin 4in secondary positions. K25G represented the alternative 5.25in DP mounting approach, being equipped with seven twin Mk 1 5.25in mountings with short trunks.²⁶

Note: The drawing of K25E was submitted to the Controller on 23 July 1936 to illustrate the general arrangement of a series of 5.25in-gun cruiser designs that formed an alternative approach to meeting the 8,000 ton cruiser requirement. K25A to K25D had the same armament and a similar general layout but incorporated trade-offs between speed and protection (see Table 1.4). K25F formed part of the same series but incorporated an additional 5.25in turret by replicating the forward turret arrangement aft. The later K25H, submitted for the Controller’s consideration on 16 September 1936, was also similar to K25E but K25G, put forward on this same date, illustrated a different configuration. All these proposals were considered by the Controller in mid-September 1936 before he decided on a shortlist of 6in and 5.25in designs from which the Sea Lords could make a final determination.

The Dido class fleet cruiser Argonaut in August 1942. The possibility of arming the 8,000-ton cruiser with 5.25in dual-purpose mountings similar to those used in the Didos was seriously considered throughout initial consideration of design options, largely due to the advocacy of the Third Sea Lord or ‘Controller’, Vice Admiral Sir Reginald G H Henderson. Henderson was impressed with the superior anti-aircraft performance offered by the 5.25in mounting, as well as the savings in personnel offered by a cruiser fitted with a dual-purpose armament. His advocacy of the weapon resulted in the K25 series of sketch designs, which all incorporated 5.25in mountings. (ADM 11043)

Controller Henderson was quick to discount sketch K27. The design of the quadruple 6in turret had yet to be completed so its selection would delay the new cruisers by a minimum of six months. Moreover, recent trials had demonstrated that the close spacing of the 6in guns in this design could result in interference between the shells in flight, causing erratic spreads. There was doubt as to the extent to which this problem could be entirely resolved. There was already concern that the triple 6in mounting proposed for K23A* might be impacted by the same phenomenon to some extent.²⁷ Moreover, the Controller considered that the ship’s main armament left her slightly under-gunned for her displacement and that the 4in anti-aircraft armament for both K27 and K23A* would be insufficient. By contrast, he was far more positive about the 5.25in armament of K25G, citing the improved anti-aircraft proficiency provided by having the guns protected by armour and the crewing efficiencies already referenced above. He also pointed out that her fourteen 5.25in guns would deliver a broadside of 9,600lbs per minute compared with the 5,600lbs of the nine 6in guns in K23A*, although he admitted that penetrating power would be less. Concluding his comments on K25G with the observation that a novel design would be ‘good generally for our prestige as leaders of design’, he expressed the view that this option best suited the nation’s needs, being confident that ‘no Commander in Chief afloat would regret having five of these ships at his beck and call’.²⁸

Note: K23A* – a modification of the previous K23A – was submitted to the Controller on 18 September 1936 to form one of three shortlisted sketch designs he decided should be considered by the Sea Lords to form the basis of the 8,000 ton cruiser. The other shortlisted designs were K27 and an iteration of the 5.25in-armed K25G, visually identical to the subsequent K25G* illustrated on page 27. Note that turret armour is not shown in the drawing of K23A* now contained in ADM 1/9402 and there is no table of particulars. The scale of protection shown for the turrets is therefore based on the previous K23A.

The Fiji class cruiser Bermuda is fitted with her ‘A’ triple Mk XXIII 6in mounting in a photograph taken on 24 May 1942, fewer than three months before she commissioned for trials. Introduced in the preceding Belfast class, the Mk XXIII was a long-trunk mounting equipped with cordite and shell hoists that ran directly from the gunhouse to the cordite handing and shell rooms, thus reducing manning requirements. The superior range and penetrating ability of the 6in gun played a key part in the selection of the K31 sketch design – equipped with this weapon – over the 5.25in-armed K25G* as the basis for the 8,000-ton cruiser in October 1936. (Crown Copyright, National Records of Scotland, UCS1-118-568-132)

It is clear, however, that the subsequent discussion did not entirely go the Controller’s way. The various arguments presented have not survived but it is apparent that none of the three options was considered entirely suitable. However, there was a potential solution. It had sometimes proved possible to achieve weight savings to the displacement of warships during the construction process. It was therefore determined that the ships could be designed at a margin above the treaty limit. The precise margin is not stated in the written records but – on the basis of the subsequent design process – it seems that around 2.5 per cent (200 tons), perhaps as much as 3.75 per cent (300 tons), was allowed. Given that a triple 6in turret and its ammunition weighed around 210 tons, this additional flexibility was significant.

Note: The 6in-gun K31 and 5.25in-gun K25G* were submitted to the Controller on 21 October 1936 following a decision that a margin above the authorised 8,000-ton displacement limit could be incoporated in the new cruiser design. K31 was a more heavily armed derivative of K23A*, while K25G* was based on the earlier K25G submitted in September but incorporated more powerful machinery. These two designs were those from which the Sea Lords made their final selection on 30 October 1936.

The DNC was given formal instructions to proceed on this basis on 16 October 1936. Alternative 6in and 5.25in designs were required. It is apparent that work on a ship armed with twelve 6in guns was already underway, with Constructor Kennet having already produced a satisfactory design two days previously.²⁹ On 21 October, DNC submitted a sketch of the twelve-gun 6in ship as K31, differing from K23A* principally in the addition of the fourth triple turret. The other main change was the adoption of a variant of the 4in HA magazine arrangement first proposed in K26, but this time with the magazine being placed between the aft boiler and engine rooms. The alternative K25G* 5.25in design passed to Controller on the same day used the additional margin to adopt more powerful machinery, allowing 31.75 knots to be achieved.³⁰ These final designs, forwarded to the Sea Lords on 22 October, are summarised in Table 1.6.

TABLE 1.6: 8,000-TON CRUISERS – FINAL DESIGN PROPOSALS TO SEA LORDS (22 OCT. 1936)

Notes:

¹. The official standard displacement was 8,000 tons but the Controller instructed the DNC that the design could be calculated at a margin over this figure. The precise margin is not stated in the files but – from the Fiji class’s design history – it seems a figure of around 200, perhaps 300 tons (2.5 per cent–3.75 per cent) was allowed.

². Calculations in W G John’s Workbook No 11 suggest K31 had waterline dimensions of 550ft x 59ft 6in x 16ft 6in. Length between perpendiculars was 526ft. Dimensions of K25G* would have been similar.

³. There is a discrepancy in the file – ADM 1/9402 – between the tabulation of the armour scheme and the accompanying sketch. The tabulation stated the turret fronts were 3½in and the sides 1in. The figures in the sketch have been used as these are consistent with previous figures quoted for design K23A, from which K31 was derived.

A photograph of Nigeria taken whilst she was laid up in reserve in August 1951. In spite of many detailed wartime alterations, her appearance remains essentially unchanged from that when first delivered in 1940. Whilst heavily influenced by the K31 sketch design approved in October 1936, it took over a year – and the production of many further design iterations – before the sketch was to be translated into the final Fiji class design. (ADM 10654)

8,000-TON CRUISER SKETCH DESIGNATIONS