So does anybody have any ideas on what the butterflies would be due to having better intelligence in a less devastating Pearl Harbor attack? I'm not planning on doing a timeline it's just a fun question.
It's been covered on a few other threads.
Broadly, there's an awful lot of room for authorial fiat, particularly with regard to how much better the intelligence is.
With a day or more of warning, the Pacific Fleet isn't caught at anchor. It may move to engage
Kido Butai, which I think is the consensus likely outcome, in which case it is attacked under weigh and takes fewer losses as maneuvering ships are harder to hit, but those that are sunk are lost in deep water and cannot be refloated as OTL, plus the loss of life is significantly higher and those crews are not available for the USN as new construction comes online. If the fleet is judged by Kimmel for whatever reason not to be in fighting trim and moves to the SE of Pearl away from KB, then it is not spotted at all and takes no losses. While at sea, the USAAF is not used to coordinating a CAP with the Navy, so there is significant chance that something will go badly wrong and any KB strike is not intercepted.
If there's some warning but still not enough to get steam up - say,
Ward rams a midget submarine and has wreckage to prove it - then there's an attack into ready defences.
If the Hawaiian Air Force does manage to scramble and engage the attacking first wave, it has a lot more fighters than the IJN does; however, only hours later Manila will be bombed despite three pursuit groups being scrambled under radar control to intercept the incoming raid because the USAAF isn't very practiced at ground-controlled intercept, so the actual strikes may go in undisturbed by US CAP. On the one hand, the US has less agile fighters and doesn't have a doctrine of boom-and-zoom. On the other, quantity has a quality all its own. Either way, if Fuchida sees fighters in the air, the second wave will be called off and the attack aborted. Probably. Readed AAA is still not great in 1941 with too many ships reliant on 1.1" or .50 cal, not enough radar, no VT fuses, and nowhere near the profusion of light AA found on USN vessels by the late war. IJN losses will be heavier, especially among the torpedo bombers, but not catastrophic.
It's B-17s that can find KB most easily, but they will all miss.
If intelligence is
really good (though I am not sure how without ASB intervention), the USN ambushes KB before dawn with heavy surface units while the strike is still being fuelled. The US battleline massively outguns the two refitted BCs, and the cruisers are faster than Nagumo's carriers. While the Long Lance torpedoes are scary, fundamentally it probably ends like S&G vs
Glorious writ large, and Japan has lost the Pacific War before the first shots in the Philippines are fired.
Butterflies - if it all ends in a wash, there aren't that many. The USN lacked oilers for its battleline to operate over the distances of the Pacific at the time anyway - they are still largely stuck at Pearl for the moment. Greater Japanese aircraft and pilot losses are not going to slow operational tempo much.
PoW and
Repulse probably are still lost, as are Singapore, the Philippines, and Burma.
