Your 10% is generous to the Germans if you only look at the breakout, two 4 torpedo launches are not much, the damaged Ajax for sure would have been relieved by the time the subs arrive, IMO the best "pocket battleship killers" the allies have are Dunquerque and Strasbourg so that would be my choice but the composition of the blokading squadron at the time the subs arrive is anybody's guess but we can assume the subs will need to disable a least a couple of big ships to give Graf Spee a chance. Those odds probably do not justify an attempt, the germans need to damage the blockaders before the breakout.
The British subs patrolling the Messina straits (yes I do know the sea bed is different, I've been skin diving in the area for the last 40 years ) managed to badly damage Trieste, Bolzano (Twice!!!) and Attendolo and sank Bande Nere, and that is what I was thinking about. When ships are tied to a single location sooner or later a sub will get a good firing solution, we are looking at someting much closer to that than to the ULTRA intercepts where the subs would only get one chance against a squadron passing trough a given area. The Royal Oak episode is also significant, if a surfaced U-Boot can get into Scapa Flow at night it can probably approach a blockading squadron with overtired lookouts after days of patrolling.
Given enough time the Germans may actually attempt something even sneakier like loading a couple of the small torpedo boats they used on the auxilliary cruisers on a merchant hull and try to ship them to the estuary, the chance of bagging a major warship and saving Graf Spee is definetly worth the risk, AFAIK those boats were originally designed to be carried by the Type III U-Boats that were never built but would have been very useful in this situation with their much better range compared to the VII.
Close blockades in the age of steam are very rare for good reasons, a big warship's best defence against torpedo armed vessels is not letting it approach, if the ship is tied to one place ......

Ark Royal, Renown, and at least 3 other CAs were headed that way prior to the scuttling. Note that Ark Royal makes the area somewhat hazardous for the subs as well. Germany was also having a lot of problems with their torpedoes at that point in time.

I think 10% is overly generous too. The reason I gave them that was because I was thinking of the Darter/Dace action in the Palawan Passage in October, 1944. In that action, two US Gato-class subs sank two Japanese heavy cruisers (Atago, Maya) and badly damaged a third (Takao). In the ensuing attempt to sink the damaged cruiser, the Darter ran aground and was lost. The sea-bottom in the area is shallow and strewn with coral reefs, although probably nowhere near as difficult for subs as the River Plate estuary. The Japanese squadron was doing only 18 knots, if I recall correctly, and was not in ASW formation, but did include destroyers. Of course, the US subs were also far more capable than the German subs, carrying ten torpedo tubes, being capable of 21 knots, and equipped with an excellent surface search radar which allowed them to pick up the cruisers in time to get into a favorable firing position.

If the Graf Spee situation is drawn out long enough to allow German subs to arrive, it must be presumed that the British will have massive forces available, including destoyers. In that case, GS is not only doomed, but most likely so are any forces the German navy can bring into play.

I agree that a close blockade of GS would probably not be attempted for the reasons you outline, once the British have had time to deploy their ships and organize their blockade. It would probably be carried out with destroyers in the estuary (because of ther shallow draft, speed, and expendability), aircraft patrols from the Ark Royal, and a distant covering force composed of a battleship/battle cruiser component and cruisers, all properly screened by destroyers. In any case, time certainly won't prove to be on the side of the GS.

I agree but if the Allies commit that strong a force the Graf Spee will never come out and the KM can claim a strategic victory, those ships, especially the carriers and destroyers, are badly needed elsewhere and if the blockade continues will need to be rotated for maintenance and resting crews, that's why I was assuming something no stronger than Dunquerque and Strasbourg.

And as to the Ark Royal making the area dangerous to subs it's perfectly true but it works both ways ....

Not true.

The Graf Spee cannot stay in Montevideo indefinitely. Uruguay leans to the allied cause in December, 1939, and would, in any case, come under intense pressure from the UK and US (it's two biggest trading partners) to intern the GS. Germany desperately wanted to avoid internment and viewed such a development as at least a propaganda defeat.

Once the GS is interned, it is out of the war and the British no longer need to maintain a blockade. Realistically, the whole matter would be resolved in less than a month.

No additional German forces could get to Montevideo before end of Jannuary, so if we assume the GS would be interned by then what happened historically is the only reasonable outcome, Graf Spee has very little chance of breaking out unassisted and no reinforcements can get there in time.

The mini schnellboote were far from ready in the discussed timeframe. Building the special torpedoes they needed was far from finished and the LS boats shipped on the raiders were used as minelayers, only the last raider (forgot the name) had a torpedo carrying LS boot.

greetings !

Aglooka

Didn't know that thanks.
Michel's boat LS-4 definetly used torpedoes, but Michel left Germany in March 42. Kormoran with LS-3 left at the end of 1940 but I can't find any documents on LS-3 firing or even having torpedoes. LS-2 on Komet was used as a minelayer and I don't think any of the other Hilfskreuzer carried boats.

BTW this is what I think is an LS alongside U-97 in Patrasso in mid 42, the shot clearly show the small size of these boats if that's what it really is.
LS-XX.jpg

Take this GRAF SPEE idea in another direction. Here's why. She was fast for her day and her 28cm guns were not to be ignored. Let's say she breaks out, regardless of limited fuel and ammunition, and she's intent on simply running the British and French forces to the ground. Any Uboot assist would be purely opportune, but allied air recon was very limited. She runs north into the North Atlantik, leading the Royal Navy on a merry chase and causing all manner of panic and confusion, disrupting merchant ship sailings, etc. This was the tactical purpose for which she was designed and built. The idea that she was too fast for any warship that could sink her and too heavily armed for any that could catch her sounds very neat, but has its flaws. Whatever the pros and cons, the Kriegsmarine tactics were a roll of the dice... some you win, some you loose. Sending her out to start with was rolling the dice against long odds of survival for any great length of time anyway. Look what happened with the BISMARCK episode... the British went bananas, and with cause. I'll venture she could have worked her way well into the North Atlantic before they caught her. What say ye?

Do we know what her fuel status was in Montevideo, and how that converts to potential range without more?

Lou

__________________

But by the time of the River Platte battle she couldn't outrun British cruisers.
She doesn't have the range to reach the North Atlantic with the damage she has taken. What's more she will likely not survive the British ships waiting for her. If she does with the additional damage she won't survive the reinforcements due in the next couple of days (they include at least one CV and one BC)
But that wasn't her design philosophy. Indeed there were quite a few ships that could catch and sink her when she was built. By WWII there were a lot more.
It's not so much the fuel that will limit her. It's things like fresh water.

i believe they did the right thing by scuttling saved lots of lives, shame the captain was forced to commit suicide.

__________________
News today, a man has fallen into a chocolate vat in the arnotts factory

In other news arnotts have anounced that there will be 50% more tim in your tim tams.
(p.s. only aussies will get this joke)