Ark Royal vs Bismark

The effect of an APC in confined spaces such as inside the ship is directly related to the size of the explosive charge (5.03lbs in case of the US 8in Mk 21 super heavy APC) and the bodyweight of the shell (272lbs in case of the Mk21) which adds about 1/3 to 1/2 of it´s weight for lateral sideways directed fragmentation. The weight of any nose coverings or AP-caps do not add as they are destroyed by prior impact (substract them from the total weight). Compared with the relevant figures known for the 11.1in APC (14.55 lbs high explosive and 538 lbs body weight), it doesn´t look like the 8in superheavy can even hope to close the gap in detonative effect. One might argue whether weight for splinters or explosive ordenance delivered is more important, british tests showed that the amount of explosive is much more important than weight and their findings are valid also in US tests.
While the effect behind plates is much better for an 8in Mk21 compared to the lighter 8in Mk18, both are significantly inferior in this regard to larger projectiles, like the 11.1in (which may also choose to use either base fused HE with 35.3 lbs HE or nose fused HE with 48.06lbs HE content to further augment effect on target).

The heavier Mk21 projectile also reduced the muzzle velocity by 200 fps with new 8in guns, this makes penetration through vertical surfaces weaker (belts, CT, turret barbettes) but there might be a range of distances, when the better energy retention partly offsets the lower initial velocity in a way that equal or almost equal striking velocities are reached. At 20,000 yards f.e., the lighter 8in APC has a striking velocity of 1227 fps and an angle of fall of 24.4 deg while the superheavy mk 21 has 1248 fps striking velocity and a somehow steeper angle of fall (25.7 deg). Generally spoken, side penetration performance is traded for deck penetration performance a slightly more pronounced destructive effect on target.
Note that it is MUCH more difficult for an 8in gun to hit something at -say 20,000 yards- than for a larger BB type of projectile.

A minor point Del but a question? With the heavier MK 21 projectile, even though the MV might be decreased, could the down range velocity be better because of a higher ballistic coefficient?

Hello Delcyros
as I wrote, of course 11" was clearly more destructive than 8" shell, but from USA 8"/55 (20.3 cm) Marks 12 and 15
US 152kg AP could still penetrate 5" side armour from 24.400y and 2" deck armour from 18.400y so IMHO AGS had no immune zone against it, Baltimore being faster it could dictate the fighting range at least as long as it machinery is intact. So both ships could hit other's vitals. So IMHO much depended on luck. And AGS 5.9"s and 4.1"s did not get even one hit during the River Plate Battle, even if Ajax and Achilles came rather close during some periods of the battle. I don't see much difference in duel between AGS and same sized CA, against smaller ones yes, but that's normal, I'd say that HMS Belfast, the last of RN pre-war CL was more powerful than Nürnberg, KM's last CL, bigger ships simply tended to be better armed and armoured than smaller ones.

Juha

With the heavier MK 21 projectile, even though the MV might be decreased, could the down range velocity be better because of a higher ballistic coefficient?

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It does my friend. From ca. 19,000 yards onwards, the striking velocity is equal or better for the heavier Mk-21 projectile. Still, this is accompanied with a more steep angle of fall and hence a worse impact obliquity condition, which partly cancels out any benefit from the higher striking velocity at this range (against vertical armour, not so when engaging deck armour). With the american ap projectile designs, with very tough hardened bodies and sheath hardeneing employed, it probably is the better solution because their projectiles are much better penetrators at high obliquity than were average ww2 ones.

US 152kg AP could still penetrate 5" side armour from 24.400y and 2" deck armour from 18.400y so IMHO AGS had no immune zone against it, Baltimore being faster it could dictate the fighting range at least as long as it machinery is intact. So both ships could hit other's vitals. So IMHO much depended on luck. And AGS 5.9"s and 4.1"s did not get even one hit during the River Plate Battle, even if Ajax and Achilles came rather close during some periods of the battle.

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The mk-21 APC can penetrate medium armour such as employed on AGS belt/barbette/turret and CT. However, the penetration figures are for vertical armour and new guns (thus without any gunwear) and 0 deg target angle. AGS belts are made from a tougher version of Wh (same as employed on the BISMARCK class main armour deck plates) and tilted back 13 deg. This impact condition would be difficult to penetrate from 20,000-21,000 yards onwards with a gun showing light gunwear and the projectile would then have not enough residual velocity and fuse delay remaining to defeat the torpedo bulkhead behind and thus would have been unable to reach the vitals at distances much above 20,000 yards via the side protection system. It may have been able to reach the machinery spaces via deck (but only via penetration of the 40mm part of it, which is a rather small area to hit) at 18,000 yards but may from ca. 23,000 yards defeat any horizontal deck of AGS (including magazine area).
The penetration of it´s splinters is 0.64 to 0.94in, which would be insufficiant to do much damage below the main deck.

The penetration ability of the 8in superheavy is somehow comparable to the 28cmL4,4 Sp.gr.m.Bdz. (base fused HE), which would have been the choice for AGS. It can defeat any of the CA´s vertical armoured surfaces out to 25,000 yards and from 22,000 yards onwards any of it´s decks. In addition it´s splinter ability ranges between 1.25in and 1.50 in for the base fused HE and put´s several spaces at risk (including main armour deck above the machinery spaces), particularely for a projectile reaching the space below the deck via sides or deck penetration in the first place. The time of flight figure is shorter (32.1 sec vs 37.2 sec at 20,000 yard) and would therefore allow a faster firing cycle at long range. The impact obliquity is less steep and while this gives away deck penetration it increases the dangerspace behind the target and thus makes hitting it more probable in the first place. A long range engagement with a single cruiser is a real don´t do against a PBB.


The destructive effect on target, owing to the larger bursting charge and the heavier body weight for splinter production is about 5 to 15 times* higher for the 11.1in base fused HE compared to an 8in AP. In this regard it´s more the competetion of a handgranade versus a .5cal BMG API cannon ball.


*) depending on whether You factor in explosive beeing more or less important compared to weight.

I was watching some old footage yesterday of carriers in rough seas, at times they were like a cork going up and down. If the Bismark and Ark royal met it would probably be in the North Sea. Would heavy seas affect a battleships guns aim before a carriers ability to launch or vice versa, did anyone record how many days flying was impossible?

Hello Delcyros
Quote: " The penetration of it´s splinters is 0.64 to 0.94in, which would be insufficiant to do much damage below the main deck."

My bet is that a 8" AP shell bursting inside a magazine could do lot of damage. And Portland's hit on Hien showed that they could wreck also machinery.

Quote: "The time of flight figure is shorter (32.1 sec vs 37.2 sec at 20,000 yard) and would therefore allow a faster firing cycle at long range."

Only during ranging, if even then, when range was found, one could, if he wanted, fire at max RoF, which was higher for 8", until one lost the range.

Quote:"However, the penetration figures are for vertical armour and new guns (thus without any gunwear) and 0 deg target angle. AGS belts are made from a tougher version of Wh (same as employed on the BISMARCK class main armour deck plates) and tilted back 13 deg..."

Thats why I gave the 5" (127mm) penetration distance, not 4" (102mm).

On the effects of 11", now they easily knocked out lightly protected RN turrets, 1" protection, but IIRC Exeter's engine spaces and magazines were unharmed even after 7 hits and numerous near misses. Same in Norfolk, hit in X-turret barbette knocked the turret out and its magazine was flooded as precaution but the hit which went trough the side and exploded on main deck over an engine room made no material damage inside the engine room and had no effect on the speed of Norfolk. Smoke from the fire in compartments on the main deck which was the result of that 11" hit forced some of engine room personnel to wear gas-masks until the fire was put out but that also had no effect on Norfolk's speed and it could continue the battle and could follow Scharnhorst during its high speed retreat and participate also the final phase of the battle. So RN armour scheme idea, whatever we think its cleverness, seemed to have worked as planned, even if ships lost part/most of their firepower, critical spaces remained untouched. But in Exeter case structural damages in fore part of hull forced in the end speed to be dropped to 18knots. But IMHO even weakly protected treaty cruisers as Norfolk were rather resilient ships. On the other hand IMHO RN's idea that 6" cruisers could smother stronger ships by avalanche of 6" shells from shortish range didn't work as advertised at River Plate.

Juha

It doesn´t take that much to disable a turret. All You need is a sufficiantly heavy projectile striking it at sufficiantly high velocity and that´s all. You don´t even need to penetrate the armour -damage inflicted by shock, spalling or plastic deformation will jam the turret, it´s roller path or throw the installation out of alignment for the remainder of the action. It may be repairable in within a few hours but that doesn´t help in the heat of a battle. AGS shrugged off three rather light 6in CPC from it´s main turrets during the action but their residual velocity was to low to inflict spalling damage or shock. Had they hit them at closer distance with higher impact force, these turrets would have been rendered unservicable or temporarely jammed. But as it was, the protection was up to the task.

The random distribution of the hits made sure that EXETER survived, not the armour protection employed in this ship. Had there been a hit on the armour deck then the splinters would have sprayed the machinery spaces below. Similarely, the hit distribution on AGS mainly centered around the CT, well above the dwl.

In order to detonate inside the magazines, a projectile either needs to come from close range or from very long ones. A surprise encounter in the night may fullfill the first one but the second one is difficult to sustain for any CA against a PBB. A detonating hit inside the magazines need to destroy a sufficiantly large number of protected magazine cases or protected brass cases in the PBB to have any effect. A hit in adjacent spaces doesn´t inflict the degree of splinterdamage to seriously threaten the magazines. Even with a direct hit, RPC/38 is a very slowly burning propellant and 5lbs of high explosive isn´t that much to trigger a rapid conflagration involving masses of propellant charges.
Once again, shells are flying both sides. In this condition, a penetrating hit into the vitals not necessarely INSIDE the magazines but also NEARBY with an 11.1in delay fused HE is all what´s needed to lit up the magazines. While US propellant is also slowly burning it is stored in silk bags with lots of them in ready rooms and handling rooms during action. Protected cases for the bags can be found in the magazines. There is no armoured bulkhead seperating the main magazines from the machinery spaces other than a single .75" STS frame,which is piercable by 11.1in fragmentation in considerable distance to the blast and these fragments still have residual energy to rip up the protected cases with the powder bags.

Protectionwise, behind the main armour of AGS is internal armour to limit -or prevent- the direct effects from impacted plates, including splinters produced by either the plate or the projectile. There is very little behind the armour in other CA´s to limit the damage. Also the ability to carry on damage is much compromised when the main belt is either not really exposed or hittable (IJN designs) or when a light list may bring the armour deck into the waves with virtually no protection above it. A straddle on AGS with 8in APC has no effect on the waterplane, while a straddle with 11.1in HE may create a number of problems and riddle the ship´s hull outside the main belt.

Rapid fire was not to be ordered until the range had been found and stabilized (requiring repeated straddles in succession) At long range this gives the PBB kind of an initial advantage (better ballistic properties of it´s projectiles thus shorter time of flight, thus faster firing cycle, better firecontroll gears and less dispersion allows a quicker fix on target, thus openeing rapid fire sooner than the opponent). It´s the close combat when the higher rof of an 8in really start to take over any advantages of the larger gun.
It takes a good deal of critical 8in hits to silence AGS but it doens´t take a lot of critical 11.1in hits to either silence or blow up a cruiser. How would You fight AGS in a single BALTIMORE?

I believe that a single CA would have to be very lucky to defeat a PBB, in a good visibility daylight battle. That is the reason I said in an earlier post that the answer to PBBs was multiple cruisers. I believe also that the British theory on CLs was that encounters, not necessarily with PBBs, would be at night or in very poor visibility conditions and the high rate of fire with many six inch guns at closer ranges would be preferable to lower rates of fire from less guns from CAs.

The CLs at the Plate had to get close to do any damage, as Del has demonstrated. In the movie, Admiral Harwood was said to have said, "We might as well be bombarding with snowballs, lets get closer." and then, as they got closer and began to register hits, "What price snowballs now!" Maybe movie hyperbole but it does illustrate the problem. The problem also now was the the CLs closing the range made it easier for AGS to hit them also and they had to withdraw. All the British cruisers were fortunate that they were not disabled like the Exeter ultimately was.

I believe the USN theory was that CAs were the answer, because in the better visibility of the Pacific, they could stand off out of the range of torpedoes and pound the enemy. In the event, with most battles taking place at night, the Japanese torpedo expertise made the USN pay heavily. The first US CAs, the Pensacolas, launched in 1929, had torpedo armament that was subsequently removed and the later designs had no torpedoes. Given the performance of American torpedoes in the first years of the war, torpedoes on CAs might have been excess baggage.

Hello Delcyros
Quote: "How would You fight AGS in a single BALTIMORE?"

Much would depend on tactical situation. Now my military training was that of Pioneer/Combat Engineer squad leader, and that decades ago and heaviest weapon of which fire I have directed was that of squad light mg, so I tended to leave naval tactics to professionals. I have very limited knowledge on USN tactical doctrines but because Wichita served in escort duties in 42 in Arctic, I guess that USN figured out best tactics for it against a PBB, but I have no idea what they were. Anyway IMHO it would be best to fight outside the best range for PBB, either longer or nearer.

Quote: "A detonating hit inside the magazines need to destroy a sufficiantly large number of protected magazine cases or protected brass cases in the PBB to have any effect."

My bet is that the likehood is that a detonation in a magazine would have forced Germans to flood the magazine and so the hit would have knocked out ½ of PBB's main turrets and all turrets in one end of the ship with all the tactical consequences. What would have been the effects of a 8" hit on PBB's engine room, I have no idea but 6" hits disabled aux. cruiser Kormoran's diesel engines completely.

On 11" shells, IMHO they weren't terrible effective historically as Norfolk showed. Especially that 11" shell that exploded above an engine room without any material damage in the engine room or any effect on Norfolk's speed. They did clean work on very lightly protected RN cruiser turrets and on Glorious, but CVs were "eggshells with tremendous firepower". If one compared them to 15" shells for ex British at Mers El Kebir or Bismarck's hit on Hood, 15" were real ship killers 11" not even reliable mission killers. IMHO PBBs were ingenious and revolutionary design when completed but were made obsolete fairly soon by advancements in radar and communication technologies and massive increase in aircraft carriers. They were simply too slow, when better radars made it very difficult to outfox a shadowing CL or a/c in bad visibility their utility diminished rapidly.



Hello Renrich
British preference of CLs didn't seem to rely on bad weather. When London Naval Treaty forced a CA building holiday and Mogamis turned RN away from small cruisers (RN had began to build small cruisers because it saw that it needed a max number of cruisers for trade protection duties and because of the fixed total cruiser tonnage meant that one got more hulls if they were smaller) they after some studies concluded that well protected CLs could overwhelm CAs even if 8" gun had longer range and heavier punch because of higher RoF of 6" gun. RN CLs didn't even had 6" APs, only Common (and HE for shore bombardments). Aim was clearly to wreck the superstructures of CA. That RN really believed that was shown that when the CA building holiday ended and other big navies began again build CAs RN didn't and continued to built only big CLs. And because the potential enemies of GB in late 30s were Italy and Japan besides Germany, I really doubt that RN would have counted solely on bad weather combat in Pacific and in Med. That the rationale was at least partly flawed was shown in Med where Italians often tried to disengage. Because their CAs were at least as fast as RN big CLs the latter could only pursuit under long range 8" fire, only hope to get near Italians were technical problems in Italian ships or lucky hit by FAA torpedo bombers. In Arctic there were some cruiser actions in bad weather and in Pacific, where RN's big CLs didn't participate any surface actions, night combats were norm because of effectiveness of a/c there.

Juha

renrich said:

A minor point Del but a question? With the heavier MK 21 projectile, even though the MV might be decreased, could the down range velocity be better because of a higher ballistic coefficient?

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I don't think the Mk21, the 335lb shell was in service until 1943 or so.

Ive always subscribed to the view tht AGS won the action, and lost the battle. Though I confess that I did not have the detailed knowledge of the actual hits and damage, the secondary sources that i have read, suggest the Langdorf had the game in his hands, and did not realize it. The British TG exited the engagement with heavy damage, the AGS with only light damage, and as Dels very detailed posts indicate, quite repairable. I subscribe to the traditional view that the AGS was scuttled because the Germans believed that the RN was waiting for them in great strength, just outside the harbour. It was not scuttled because of "ireparable damage"

The PBs were a solution to getting a great deal of firepower to sea, with moderate protection. Their great advantage was their range and firepower....their protection was good, but not invulnerable. There speed was also at best only adequate. They would have been far more dangerous if their speed was 3 or 4 knots more than it was...ie about 30-32 knots

I dont believe the british cruisers were up to the task of defeating her in 1939. I am not so sure about how the AGS would have fared against the heavier cruisers of the later war period......

parsifal said:

Ive always subscribed to the view tht AGS won the action, and lost the battle. Though I confess that I did not have the detailed knowledge of the actual hits and damage, the secondary sources that i have read, suggest the Langdorf had the game in his hands, and did not realize it. The British TG exited the engagement with heavy damage, the AGS with only light damage, and as Dels very detailed posts indicate, quite repairable. I subscribe to the traditional view that the AGS was scuttled because the Germans believed that the RN was waiting for them in great strength, just outside the harbour. It was not scuttled because of "ireparable damage"

The PBs were a solution to getting a great deal of firepower to sea, with moderate protection. Their great advantage was their range and firepower....their protection was good, but not invulnerable. There speed was also at best only adequate. They would have been far more dangerous if their speed was 3 or 4 knots more than it was...ie about 30-32 knots

I dont believe the british cruisers were up to the task of defeating her in 1939. I am not so sure about how the AGS would have fared against the heavier cruisers of the later war period......

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As long as there was either Ajax or Achillies at sea and able to make full speed the Graf Spee had lost. GS was a surface raider her job was to sink merchantmen, taking on the RN wasnt a sensible proposition. Even if GS had left the harbour she couldnt have made it back to Europe without a further confrontation, the game was up.

tail end charlie said:

As long as there was either Ajax or Achillies at sea and able to make full speed the Graf Spee had lost. GS was a surface raider her job was to sink merchantmen, taking on the RN wasnt a sensible proposition. Even if GS had left the harbour she couldnt have made it back to Europe without a further confrontation, the game was up.

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I agree that AGS position was severely threatened whilst shadowers remained in her wake, however it was definately not a foregone conclusion that she was lost if shadowers were present. RN heavy units (principally the Ark Royal and the Renown) were more than a week distant, and would have been very short of fuel on arrival. The Ark Royals CAG was lacking in experience as far as night operations were concerned, and would not have been as efficient as they were when attacking the Bismarck.

All the AGS had to do was to put to sea, and put the hammers down. Two days later the Ajax and Achilles would have needed to break off for lack of fuel....and AGS disappears again into the South Atlantic. I see the chances for her survival as very good actually. Her loss at the hands of her own crew was a totally avoidable loss IMO.

Hello Parsifal
Yes, also I think that AGS won the action but that was a kind of Pyrrhic victory. Some of the damage forced Langsdorff to flee to Montevideo and fleeing to neutral harbour with shadowing ships still following means that he was located and more powerful enemy ships were to be sent there. What was the damage that forced Langsdorff to Montevideo. It must be something that was not repairable by ship's own mean. One was probably the hole in stem another was probably the damage to the auxiliary boilers or to their stacks. On the latter info from numerous posts from much more knowledge persons than I to one discussion board, a bit clip and paste.

Quote: "…However, the fuel, which had been bought from the US in the summer of 1939, caused numerous complaints from Langsdorff due to water and particulate contamination. It would also appear the microbial contamination was present as well. This meant the fuel could not be burned without going through proper filtration (the usual fuel filters and the centrifugal separators). These were powered by high pressure steam from auxiliary boilers and these had been put out of action by splinters from a hit. Besides fuel filtration, these auxiliaries also provided steam for the lube oil filtration system, heating (which though academic in the tropics would be good to have for the trip home), fresh water production, and fire fighting. At the beginning of the action the ready to use tanks had about 16 hours of burnable fuel and the damage to the boiler piping was such that in port repairs would be necessary..."


Quote: "And this is what I've got from Joseph Gilbey's latest book Kriegsmarine: Admiral Reader's Navy: a broken dream (c) 2005

I will provide the full relevant quote at page 126:
" Spee's main engines used diesel fuel stored in bunkers around the hull. The raw refinery diesel needed treatment before feeding the engines. A separating system routinely pre cleaned the fuel and deposited it in six ready tanks, situated close to the engines. The fuel separators used high-pressure steam to function. Two auxiliary boilers and a network of valves and tubes generated the steam. The Hilfskesselraum (boiler- room) that produced the steam lay between decks, aft of the funnel. Unfortunately the Hilfskesselraum lay above the armored deck. Exeter's early 8-inch hit had wrecked the boiler-room - in effect shutting down the separating system."

Professor Eric Grove, the well known specialist, wrote in "The Price of Disobedience":

At 0736 hrs, Graf Spee re-engaged Ajax and Achilles on the port side. Both ships claimed hits, but the Germans only recorded one 6-in. hit on the hull of the ship from port. It hit the cutter on that side of the ship before detonating in the ventilation hatch to number three engine room. This was quite a serious hit which damaged the chain hoist to the port 5.9-in. armament and inflicted heavy splinter damage on the auxiliary boiler stack

Professor Grove later adds: The key auxiliary boiler that supplied steam to the distilling plant for fresh water and the fuel and lubricating oil purifier(was also out of action

Sir Eugen Millington Drake inquires about on page 307 of his masterpiece, The Drama of Graff Spee: " With regard to the auxiliary boiler, the Chief Engineer, Commander Klepp wrote to me explaining that it was above the armoured deck and that is supplied steam not only to the distilling plant (for producing fresh water) but also to the plant for purifying both fuel and lubricating oil; and that neither of these two plants themselves were damaged but only this auxiliary boiler which was, however, essential to the functioning of both.

(....) this damage consisted consisted mainly in numberless holes caused by splinters in the funnel of this boiler and, in any case, could be repaired with the means on board. This was in fact done by the Saturday." …"

That means on 16 Dec, ie a day before the scuttling, so much latter than the 16 hours time limit for purefied fuel.

So sometimes on 16 Dec was the earliest possible time to AGS to break out but was the hole in the stem repaired by then? And British play with their merchant ships meant that outbreak had to be done in daytime 17 Dec, again IIRC. IIRC Ark and Renown were to arrive on 19 Dec. My guess is that there would have been good chance that Ark's planes would have found AGS ifit had succeeded to slip away from Force G ships. And Renown was effective ship gunnerywise.

HMS Cumberland reported to Harwood at 2200 Thursday the 14th.

Juha

I don't know why this is being ignored by most of youall posting on this subject but it is my impression that Cumberland had arrived from the Falklands to join Ajax and Achilles. Cumberland was a 10000 ton, County Class. She was full sized, unlike Exeter, with eight, eight inch guns. Knowing something of the RN and it's tradition, I am sure that Cumberland would have pitched in along with Ajax and Achilles and it is absolutely problematic about whether AGS would have survived that encounter, much less eluded all pursuers to reach Europe. There were a number of Hunting Groups assembled already to intercept her, one on the US, southeast coast.

I am sure there was an encounter between a CL, perhaps Sheffield, in the Arctic Sea, against a PBB, (Lutzow?) where the weather was terrible and the RN caught the PBB by surprise, deluged her with six inch shells and the German Raider withdrew in the bad visibility. Perhaps Del can relate that episode.

My point is that the role of AGS had changed from a surface raider to persued ship. Whether she could have made it back to Europe or not is debateable but I have not read anything about her resuming singing merchantmen, in that respect the RN won.

Hello Renrich
yes, Cumberland was one of County class CAs and it joined Ajax and Achilles and arrived straight from Falkland, so its fuel situation must have been good. It was one of Kents and had got thicker side armour, 4½", around its machinery spaces during its late 30s refit. So now Force G had 2 extra 8" guns but it also had 2 less 6" guns (IIRC the crew of Ajax had succeeded to free the jammed Y turret but its X turret was still disabled) when compared to situation on 13 Dec. and it prepared to action when AGS moved out of Montevideo harbour on 17 Dec.

Sheffield and one other CL surprised Hipper when it and Lutzow plus some 6 KM DDs attacked convoy JW51A. RN CLs hit Hipper thrice and one hit put out one of its boiler room and sunk one KM DD, forcing Germans to retreat. Sheffield, Belfast and Norfolk, the latter was a County class CA, fought Scharnhorst during its attack on JW 55 and shadowed it after two brief gunnery duels when Sch. retreated straight to the approaching RN battlegroup including BB Duke of York and CL Jamaica.

Hello TEC
Yes, even if RN cruisers got worst of it on 13 Dec but AGS couldn't disable Ajax and Achilles so much that it could have freed itself from them

Juha

Juha said:

Hello Renrich

Hello TEC
Yes, even if RN cruisers got worst of it on 13 Dec but AGS couldn't disable Ajax and Achilles so much that it could have freed itself from them

Juha

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Juha

IMO the strategy of a pocket battleship hadnt been thought through and was like many things changed by aircraft. AGS needed fuel ammunition and supplies which can be supplied in a port or by vessel. In a port her wherabouts are known to the RN and using vessels at sea means the supply vessels are as valuable as the AGS herself.

Ammunition and fuel. Logistics and a well mislead tactical perception lead Langsdorff decision to scuttle AGS. Officially, it was considered an avoidable loss but avoidable is just one possibility out of many involved here.
The crux for AJAX ACHILLES was their respective ammunition state. During the battle, both CL´s emptied up their magazines at a rapid rate. In the evening, they already tried to conserve ammunition and only shadowed AGS. Both cruisers had mainly nose fused HE remaining, a few inert drill and some inert practice rounds left in their magazines next to a negliable amount of CPC. CUMBERLAND still had a near full outfit to it´s disposal and AGS was full on APC but dpleted it´s base fused HE and most of the nose fused HE outfit. Thus it would have needed to direct it´s APC against CUMBERLAND with much less splintereffects than the base fused HE to be used before against EXETER. Altough there were enough fuel and ammunition supply ships in the south atlantic at that time, Langsdorff needs to rendeveauz with them in the first place and he needs to escape Harwood before trying to do this.

A problem may occur in terms of tectical awareness for the british side. AGS alone had a functioning radar gunlaying set onboard (river plate was the first case of radar aided gunfire in a naval encounter) and appearently it was also used in the night to track other ships or to screen in front of AGS for shipping. This gives a tactical advantage in dark nights, in which AGS may use this capability to slip through, avoiding any contact. Once broken, contact is difficult to reestablish but then again, ARK ROYAL may have been the critical factor to find AGS in the open ocean again.
Langsdorff also expected RENOWN to be there and this ship is a PBB-killer.

Hello
AGS' ammo state after 13 Dec action:
full stock of 2 and 3,7cm
423 rounds of 15cm
378 rounds of 28cm
2470 rounds of 10,5cm

Ajax had expended 823 rounds, a bit over half of its 6" ammo (it had 200rpg), during the action. All I could find easily on Achilles' expenditure was that its X turret used 287 rounds and that altogether it had expended some 1200 6" rounds. So Ajax had appr. 777 6" rounds left and Achilles only some 400. My understanding is that RN CLs carried normally only CPCs (plus few drill and practice rounds), HEs were carried only if there was possibility for some shore bombardment tasks.

British sailings of merchant ships had ensured that AGS had to leave from Montevideo in daylight of 17 Dec, but its right to stay expired at 8pm, so late in the day, in fact only appr one hour before sundown. So Langsdorff would probably had possibility to loiter just outside Montevideo until sundown, after that much depended on weather, moon state, effects of lights on land etc. But because AGS' Chief Gunnery Officer had thought that he had seen Renown and Ark from the foretop on 15 Dec IMHO the decision to scuttle was logical.

Juha