I do not understand the 'non friction world' comment, Jacques, but I assume it to mean that there will be perfect transition of PoW material into japanese and german hands.
I'll deal with ULTRA first, this is the big issue and I think we all agree that it will attract a lot of attention and go up the chain very fast. It will be validated quickly, and then they will start countermeasures. Remember that you and I have already ruled out the JA using what they know to spring a strategic surprise on the Allies similar to the one the USN sprang ont eh JA at Midway.

So we are significantly discounting JA use of that data.

They will preserve everything else and duplicate it after it is recovered. The IJN will go first for the RN tactical manuals (which contain how the RN expects to fight). These will be used to re-evaluate their own tactics and to exploit for weaknesses. That will take some time, but teh IJN was a service which derived from the RN, and there is a significant pool of retired officers with good English skills for that very reason. Togo himself only died in 1940, adn a LOT of his staff officers were still doddering about.

The technical stuff will be sent to the various technical authorities. We can expect Professor Yagi and the Imperial Uni crew to get into the radar stuff (along with the IJN staff and IJA staffs responsible) and they will start looking through them for handy hints and what the enemy is up to.

This will be parallelled across all the technical specialities.

The Japanese ran quite a good technical intel evaluation program for captured equipment. The various items raised form the ship will be evaluated via those existing channels.

The Germans will want in, and will offer various experts and such. How far this goes I have no idea, but the JA just got a terrific lever to pry more out of the germans with. They would be crazy not to use it on things like Russ's ideas regarding the reactivation of their synthetic fuels program.

Does this translate into the IJN fielding copies of Allied radars in mid-late 1942? Of course not, but it DOES mean the IJN having BETTER radars than in OTL, and sooner rather than later. Does it mean VT fuses? probably not for teh Japanese. But it does mean simple things like RN style DC fuses, an impetus to their A/S warfare field etc.

We should also not forget that compared to the IJN in some areas, the RN was rather behind the IJN. Their submarines held no surprises, their torpedo tactics were primitive and their systems less than mediocre, their fleet aviation concepts were behind etc, but their concept of radar controlled intercept was ahead of them.

BUt I still consider that the loss of PoW in such circumstances and in water so shallow was the most significant single event of FFO. It will have a striking effect on FFO and we really have not discussed the wheres and whys of what happens yet.

I think we need to. it will help in our forward planning.

Cheers: Mark