The Washington Naval Treaty of February 1922 defined the basics of warship construction and design for the next 20 years. Moreover it rearranged and then conserved the relative strength of the world power navies. In addition it prevented a new armsrace just after the conclusion of the Great War. This also meant that the five signatory powers (USA, UK, Japan, France, Italy) had to give up capital ship construction – and ships being built were all bigger, better, faster and more powerful than what the World has ever seen before. I would like to introduce a few of these white elephants, the wet dreams of naval enthusiasts.
The LEXINGTON class
Ideas and the first plans
First let’s take a brief look at the historical, tactical and strategical aspects leading up to and later on shaping the LEXINGTONs.
The history of the United States Navy’s one and only battlecruiser class dates back to the wargames held by the Naval Academy in 1903. During this event the planners envisioned and tested during the games a fast big ship, with battleship level armour and guns – in this case four 12”/305mm guns. The ship acted as a scout or van of the battleship’s battleline and it’s task was to penetrate the enemy’s defensive ring of smaller cruisers and destroyers. The heavy guns were needed to have a stand-off capability due to the new generation of longer range topredoes and of course to have overwhelming firepower against smaller ships. The armour part was more questionable and even as late as 1906 and 1908 naval war games the strategist were debating the value of it. All agreed that they want higher speed but it was unclear weather they should shave off from the armour or reduce the armament to reach this goal. In the end the decision was made to minimize the armour and increase the speed substantially as by 1908 the dreadnought type ships were all capable of sustained 21 knots speed. 25% of margin was the requirement above that speed, so that meant at least 25-26 knots in all weather conditions, meaning 27-28 knots in a dead calm.
In the first take Preliminary Design department of the Navy’s Design Bureau made 6 sketches, all derived from the 1909 WYOMING class battleships which represented the cutting edge in battleship design at the time. All the preliminary designs had a common feature, a long and deep hull which was needed to reach high speeds. As usual when scaling down larger ships a lot had to be given up to reach the desired speed and still displacements reached up to 24-26.000 tons, despite the armament being only 6-10 main guns in twin turrets. Armor had to be reduced to 8-11”/203-280mm maximum. The most roboust plan called for a 198 meters long ship armed with 5 X 2 guns (12”/305mm) and an 8”/203mm belt armour (the WYOMING class BBs had 11”/280mm).
In the meantime the Royal Navy and the German Kaiserliche Marine were busy building their own battlecruisers but American reaction was triggered only when Japan announced the order of battlecruiser KONGO from Vickers Ltd.
The Navy’s leadership announced the next day the requirements for a new design: 29 knots speed, 8 X 14”/356mm guns and 24 X 5”/127mm guns in the 30.000 tons range.
The answer from Preliminary Design came in July 1912 in the form of a complete „spectrum study” as the USN designers called it. They investigated several options and the combination of all of them. Namely they took the speeds of 26, 29 and 32 kntos with a range of 7, 8, 9 or 11.000nm combined with 8”/203mm, 11”/280mm and 14”/356mm belt armour – and all possible combinations of this. Even the smallest version came out at 228,6 meters and 29.300 tons. At the other end of the spectrum stood a real monstrosity with 381 meters waterline length and 79.000 tons displacement!
This study showed very well that a battlecruiser based on american design principles (i.e long range, fixed percentage of waterline belt length) would result in a fairly large ship. The armament was still 8 pieces of 14”/356mm guns in all the variants. Remarkable is the layout of the main armoured deck as it was the main strength element, the load bearer of the very long hulls (even by today’s standards, let alone early 1910s).
The higher they placed it within the ship the more efficient it was in it’s strength giving role. Due to center of gravity issues the only way they could solve this was to only raise the armoured deck to main deck level in the middle, over the machinery and magazines and it dropped back to 2nd deck level at the bow and stern. It was sort of a squared turtle back. This way they had the deck high where it counted the most and still cut down the CG somewhat.
This solution also meant a very high rising belt armour (as it had to meet the armoured deck’s edge at the sides) and although the belt thicknesses listed were not exceptionally thick they covered a much larger area than on contemporary battleships – making these designs in reality better armoured than battleships.
The other headache for the designers was finding space for the amount of propulsion power needed to drive these huge vessels. Here enter the very long and deep hulls which were exactly what was needed because for a given cross section the longer the hull the less propulsion power it needs for a given speed. This is due to the lesser wave making resistance of the longer hull. At the same time the turbines and boilers had to fit below the armoured deck – this meant a maximum of 110.000 SHP total calculated with one turbine per shaft; anything more required more turbines per shaft or larger diameter turbines that in order needed higher freeboard (again a benefit of the squared turtle layout).
These designs were rather crude though and they were very heavy for what they offered, thanks in no small part to their battleship ancestry – fittings, scantlings, weight margins, calculations were all based on battleship building practices. No wonder that the finally accepted designs were reached from scaling up cruiser sized ships – as we will see shortly.
In 1912 the General Board was still undecided about the viability of the battlecruiser concenpt as tactical manuvers tried on the wargaming boards showed that higher speeds could be countered with basic battleline manuvers. However the laying down of 4 Japanese battlecruisers at that time and the increasing popularity of the type in the World’s navies bent the Board’s opinion toward getting such units. Therefore in 1914 the planners wanted to have 2 vessels ordered but in the end the Navy’s secretary Daniels decided that it is a total waste of money to spend on such white elephants, one-off ships that are only usable for secondary tasks. Priority was still granted for battleships (he was a politician after all, he should know better then some navy guys..).
By 1915 the ongoing world war drastically changed things. In what was know as Congress’ preparedness campaign the Navy expected some serious spending and enlargement of the fleet. Navy planners could think for the first time in a well balanced fleet expanded with small and large cruisers which differed considerably from the previous battleship centric viewpoint. The British and German battlecruisers faired very well so far in the war and Congress liked the type (in a typical political manner – the battlecruiser name sounded less agressive compared to battleship…never mind that it costed the same or more).
Due to Congressional support the huge fleet plan of 1916 included no less than 6 battlcruisers next to 10 battleships – the goal was to reach parity with the Royal Navy by 1925 and also to suplement the existing battlefleet with battlecruisers – an additional 4 units (on top of the 6).
In a cruel twist of fate the law makers voted on the 2nd of July 1916 about this 5 year fleet plan (the biggest so far), the very same day when news about the battle of Jutland started to arrive – where the RN lost 3 of it’s battlecruisers to enemy fire. Therefore the House only ratified the 6 battlecruisers originally planned and dropped the 4 extra units. 4 were authorized for the fiscal year 1917 and one for each 1918 and 1919.
Strategic needs and tactics
In 1915 it was crystal clear the US Navy was badly in need of scout cruisers or scout assets in general. The existing fleet of dreadnoughts (all weighing in at 25-30.000 tons) could only rely on a huge fleet of destroyers (most around the 1.000 tons mark, many even smaller). Inbetween there were only a handful of outdated armoured cruisers that were barely faster than the dreadnoughts (22-23 knots), moreover these had all triple expansion propulsion (meaning much lower sustained speeds) and medium caliber batteries that were useless against modern battleships and too slow firing versus smaller ships. To address the situation the Navy had previously ordered 3 experimental cruisers that were fast (CHESTER class) but these proved to be a failure as during real fleet manuvers they couldn’t keep their 5 knots speed advantage for longer periods, especially in bad weather.
In order to have a successful fast scout a large, roboust ship was needed that could maintain high speed (aim was for 35 knot) for long periods and independent of the weather.
While the General Board was still not 100% convinced for the type it transpired from many USN fleet excercises that the existing force was utterly inefficient in scouting, to the point that destroyers were regularly pushed to the scouting role. Strategic Problem No.1 of January 1915 was a prime example. With not even particularly rough sea conditions the scouting destroyers were reduced to 15 then to 10 knots and finally had to retire – while at the same time the main force of battleships easily made 19 knots, completely blindfolded though! As a result the old pre-dreadnoughts that were playing the function of RED, that is agressor fleet could reach their destination totally unmolested – they were simply not detected by protecting BLUE fleet of dreadnoughts. This highlighted again the uselessness of a strong force of dreadnoughts without necessary scouting assets. What’s more in Manoever No. 2 of Sept 1915 a superior force of BLUE was destroyed piecemail by a less strong RED, due to lack of offensive scouting and screening – BLUE had to deploy along the whole Eastern Coast to defend the shores from a concentrated attack of RED – the reason was lack of scouts and therefore the inability to strike on their own terms.
One can imagine that what advantages could be gained if one could deprive the attacking force (in this case RED) of it’s own scouting assets, exactly to reverse this scenario. Furthermore once action was joined between the main force of battleships the battlecruisers were essential in forcing the enemy to fight on BLUE’s terms by capping their T and chasing down fleeing forces – both thanks to their much higher speeds.
It is also worthy to note that these drills showed the advantages of using the most powerful armament on the battlecruisers, both to be able to threaten even the strongest battleships (fear factor) and also to be able to engage effectively from the longest possible distances, landing decisive early hits.
All these factors together pointed in the direction of the heaviest possible guns with the highest possible speeds on big hulls, with armor protection taking second importance only (and actually early sea battles of WWI underpinned this thinking to a large degree).
Between April-July 1915 an amazing amount of preliminary design work was invested to develop the type of ship the navy strategists wanted. Some 50+ designs were made alltogether with versions ranging from lowly 10.000 tons with 6”/152mm guns up to 50.000+ tons and 16”/406mm guns that were fast battleships in everything but name. We can divide up these into 3 major groups.
There came some last attempts (for the time being) at producing an all around well balanced battlecruiser. These were Designs No. 133, 140 and 143 (probably there were more but we only have evidence for these). No. 133 was the enormous giant with eight 16”/406mm guns, a 13”/334mm belt tapering to 10”/224mm then 8”/203mm with decks being 3.5”/90mm main- and 1.5”/38mm 2nd deck – all this capable of 29 knots and displacing 56,600 tons. Also noteworthy is the very heavy funnel uptake protection with 15”/381mm (!) plating on it, supposedly to protect boiler ventilation and keep high speed capability in face of direct hits on the funnel area.
In essence this was a stretched standard type battleship with better deck protection but lacking the 5 layer TDS and being 8 knots faster. The problem with it apart from it’s humungous size (324m at waterline!) and stellar cost was that it wasn’t particularly fast for a true battlecruiser and it was also lacking somewhat in the torpedo protection department (presumably to save at least some weight).
Design 140 was a somewhat toned down version with a unique armor arrangement and a much shorter forecastle deck – both to save weight. Machinery spaces were further subdivided as indicated by 3 funnels instead of 2. Belt and deck armors were combined into a continous deck (see 2nd armor scheme on Fig.4). The horizontal deck part in the midle was 5”/127mm thick which sloped down at the sides at about 55-60 degrees and thickening to 8”/203mm then when it reached the side plating under the waterline it went into vertical and thickened to 10”/224mm (tapering back to 8”/203mm at the lower end). It formed a very interesting hump-back like armor but left the sides totally unprotected at and above the waterline. The rest of the armor was comparable to the previous design. The saved weight allowed for a 52.000 ton displacement and a one knot gain over design No. 133.
It was still way too large and expensive so 1st of July brought a much reduced version (No. 143), with only 6 main guns in twin turrets and secondary battery cut to 14 mountings (6”/152mm guns) from 20. To keep weights within acceptable levels the side belt was completely sacrificed and vertical protection was limited to barbettes, conning tower and funnel uptakes only (though these were kept at full thickness). To compensate for this the uniform 5”/127mm deck was raised back one level and some form of torpedo protection was added with a 2”/51mm thick holding bulkhead. The shorter, lighter hull required less power so 30 knots was deemed possible on a displacement of 30.000 tons.
At this point the design train of thought merged with the other leg, which were called battlescouts, creating a new category that never actally materialized. If the above 3 designs can be considered closer to the German type of battlecruisers then the battlescouts were definitely much closer to the British ideas (see later).
These were the forerunners to the battlescouts, designs clearly scaled up from light cruiser hulls and armament, first with the addition of a big, seaworthy hull then some combination of a small amount of heavy guns and in some cases protection. These are all marked as Scout Cruiser on their respective Spring Style drawings.
(Unfortunately no comprehensive list of drawings is available at the writing of this article so quite a lot are missing but since the differences are realtively small we have a good picture of what was studied. Designs No. 101-111 presumably covered light cruisers in the 5-8000 tons range leading up to the OMAHA class. They were drawn in mid-1914.)
The first relevant designs ran from No. 112 to 120 then No. 122 – 126, all prepared in April 1915. The second batch ran from No.s 121, 127 to 135, exclusively made in May 1915. They all offered tradeoffs, starting with virtually unprotected ships then adding armament then adding some form of protection – all while keeping very high speeds, 35 knots in almost every cases.
No. 112 and 113 were the smallest with only 10.500 tons – armament consisted of a uniform quick firing 6”/152mm battey in ten single open deck mounts distributed on the main deck along the length of the ship. Design No. 112 offered no protection whatsoever except for a double bottom but maintained very high freeboard with a downward sloping aft deck – this solution avoided a break in the hull so in essence it was flush decker but still saved weight by reducing height aft (just like some later Japanese CAs).
Design No. 113 added a 4”/102mm belt and 1.5”/38mm deck armor over boilers and machinery but speed had to drop to 32.5 kntos. (Design No. 114 restored this to 35kn at the cost of 2100 tons extra weight.) Despite their small displacement these would have been fairly long ships at 214m+ waterline length, in order to supplement high sustained speeds independent of wave conditions. Thanks to their big size they could offer accomodation to 1000 extra men in addition to crew and could handle 6 aircraft with catapults! They also offered an unprecedented 25.000 miles range at 10 knots that obviously would have came in handy when scouting in the vast Pacific.
No. 116 and 117 offered even more protection (8”/203mm belt in the latter) but displacement grew to 13.750 and 17.650 tons respectively.
Sensing that the 6”/152mm battery might not be enough, preliminary design offered an initial variant (No. 115) with four 12”/305mm guns in 2 two-gun mountings (6”/152mm battery reduced to seven mounts). To keep weights down the 12”/305mm mounts only had a gun shield and were mostly open (pencilled in roofs on the drawing might indicate some weather protection). Only armour was 6”/152mm protection for the barbettes of the 12”/305mm mounts. This one came in at a fairly good 12.600 tons while still keeping 35 knots. No. 118 offered fully enclosed turrets for the main guns and 5”/127mm guns replacing the 6”/152mm ones while adding some beam for better stability (14.350tons).
As we can see the size of these designs already started to increase substantially with the introduction of battleship caliber main guns, despite having no or very limited protection. Still it was deemed worthwile as the 12”/305mm guns offered an incomparably greater punch.
The list of variants however was far from done as the size escalated past of earlier generation dreadnoughts. No. 119 and 120 added back protection to No. 118, with 120 having 8”/203mm belt while displacing 22,850 tons.
Then came the 14”/356mm gun as an option, with No. 122 adopting one twin bow turret and no protection – subsequent variants up to No. 126 adding back protection and a second turret aft, while displacement rose to a round 25.000 tons, not too far off from current dreadnought size – indicating the cost of very high speed. And this was on cruiser construction standard hulls!
In May the series continued, first with some cut back designs: No. 127 having two 14”/356mm guns in single turrets fore and aft while No. 135 having 2X2 16”/406mm guns and no other guns et all. Protection was omitted from both. In the subsequent variants these were upgraded with more secondaries and armor, the largest, No. 132 offering best of all with four 16”/406mm guns, 8”/203mm belt and 35 knots on a stunning 26.800 tons, an increase of 16.300 tons over the base line No. 112 variant!
The battlescout name indicates very well the intention that created this type – to comply exactly with the needs arising from fleet manuvers described in the previous chapter. What this meant in reality was a British style battlecruiser in essence and the name was made up really to differentiate from the previously described, relatively well armoured designs. These designs grew out of the merging of the reduced size Battlecruiser (1.) with Scout Cruisers (2.). They are all marked as Battle Scout on their respective SS drawings (except No 146. which is still listed as Scout Cruiser). The six listed designs were completed during June-October 1915. There are also two fairly small light cruisers in this series (No. 142 and 151) giving an interesting contrast.
Design 141 started the series with a full length straight flush decker hull (266m length!), two 16”/406mm twin turrets, 10 of the previous single open mount 6”/152mm guns and mediocre protection (4”/102mm belt, no deck and 5-6”/127-152mm on turrets) – but still with 35 knots speed, requireing 3 funnels.
On the 9th of September design No. 144 of 32.000 tons was produced, bringing features from both the heavy battlecruiser and the smaller scout cruiser designs – and it was the first variant vaguely resembling the version actually selected for production (and as such can be considered the actual starting point for what became the LEXINGTON class). The biggest difference was a reversion to 14”/356mm main guns. This reduction had to be taken in order to provide 8 guns, the minimum desirable for effective long range firing without increasing the displacement too much and also this was the then average armament for foreign battlecruisers. Also a uniform 5”/127mm belt and 4-6”/102-152mm turret armor was provided which offered at least some moderate protection. Four huge centerline funnels served the 218.000 SHP powerplant. Also notworthy is the downward sloping main deck line aft, a feature inherited clearly from the scout cruiser designs of No. 112&13. An alternative design No. 146 reduced weight to 28.000 tons, through sacrificing gun power: main armament was 4 twin 10”/224mm turrets only.
No. 150 was the refinement of No. 144 which laid out a medium sized battlecruiser – and this version was chosen for further development by relevant decision makers. The date was 28th Sept 1915.
Two more versions, No. 152 and 153 were produced to investigate the possibilities of arranging the 8 guns of the main battery in quad and triple turrets respectively. The weight saved by this way allowed for the lengthening of the main belt to the full waterline length in the quad turret variant and forward to the bow in the triple turret variant (it had the triple-twin-triple arrangement).
It can be seen that speed and firepower was emphasized over protection in all but the very big battlecruiser designs. Armor was mostly limited to 5”-6”/127-152mm maximum and no torpedo defense systems were incorporated which is a dangerous thing for long ships with huge machinery spaces in the middle, prone to flooding. So a lot of room for improvement remained to produce a detailed, refined design.