What if the Japanese fleet had been destroyed on Dec 6th 1941?

Imagine that America knew all about the impending attack on Pearl Harbour. The Japanese fleet walks into a trap, and is almost totally destroyed (a sub or two escape). America makes use of this and does NOT declare war. What does Japan do, and how does this affect the European theatre?

Well, I guess the USS Nimitz would try to contact Pearl Harbor before approaching, out of concern that their unfamiliar appearance might get them attacked…

A short story was written on this topic. Jimmy Doolittle presciently puts 2 and 2 together before the attack, and trains an entire squadron of B-17’s to glide bomb ships at low altitudes (vs. the high altitude runs they-unsuccessfully-used during Midway). He finds Kido Butai early in the morning of December 7th (right where he suspected they would be) and bombs the holy hell out of them-sinks 2 of the CVs and damages most of the rest, which turn around and slink home. But the author posits that, without a Pearl Harbor to galvanize morale and stoke outrage, both the Pacific and Atlantic wars take longer for the Allies to win and cost a lot more lives.

I read something similar in Alternate Histories, but unlike there, I’m postulating that the Japanese fleet is almost entirely destroyed and America does not declare war.

I’m kinda curious if the U.S. would keep trying to use battleship tactics (having avoided losing any on December 7th) and would eventually lose them at sea to Japanese carriers, with total loss of their crews and such. That’d hurt quite a bit. By the time they get around to improving carriers and planes, they’re pretty far behind, steadily lose engagements, etc.

I don’t get why war wouldn’t be declared; I don’t see how this could plausibly happen.

The US Navy was well aware of the value of aircraft carriers and was improving them and planes before entering the war. The Two Ocean Navy Act enacted on July 19, 1940 authorized the construction of 18 aircraft carriers. 11 of the 16 Essex class fleet carriers commissioned during the war that formed the backbone of the fast carrier task forces were ordered before Dec 7, 1941.

Huh. I stand enlightened.

Yeah, even if the US would had destroyed the Japanese fleet early on, it is very unlikely that war would not had been declared, after all it would had been clear that a sneaky and undeclared war attack was going to take place; IMHO then the USA would had accelerated the island hopping campaign as it would had been easier to do with a crippled Japanese Fleet.

Surely a war declaration would be absolutely necessary, considering that, in this scenario, the US would be the one launching the pre-emptive strike.

Not quite, at the same time Japan attacked Malaya, Thailand, the Philippines, Singapore and other locations, defeating the Japanese close to Pearl Harbor would had been a great bit of good news on that grim day. I would also think that a defeat of the Japanese main fleet at Pearl Harbor would had led the Japanese to avoid reaching too far, for example, the invasion of Singapore would not had gone forward.

That doesn’t make sense. They had already landed in Malaysia, and it would have been the same cakewalk to go to the tip of the peninsula and take Singapore. Now, the Dutch East Indies, on the other hand…

Well, the thing is that I do remember that the Japanese commander was considering retreating from Singapore when suddenly the allied force there surrendered. I figure that retreat would had been done early knowing by then that most of the fleet was destroyed.

At the most, the Singapore garrison MIGHT have put a longer fight (don’t forget they were green troops, while the Japanese were veterans with special jungle training). But counting on the US fleet to come to their help ? Please ! The fleet would have gone to help the Philippines first ! Although the few ships the British had in the Indian ocean MIGHT have intervened (to be sunk around Singapore and suffer the fate of the Prince of Wales and the Repulse) and delayed the surrender. It would have delayed or made impossible the invasion of the DEI and probably hampered the invasion of Burma also.

Huh? Shouldn’t CAP have torn the B 17s to shreads? No long range escort at this point and as 1942 to 1943 in Europe showed, B-17s were quite vulnerable unescorted.

While the B-17 was basically useless in an anti-ship role, they proved extremely difficult for the Japanese to shoot down, largely because the Zero sacrificed firepower and survivability in order to achieve its exceptional maneuverability and range. That said I have a hard time seeing the B-17 being very effective at glide bombing.

Going back to the US ordering most of the fleet carriers that won the war before the Japanese attack on Dec 7, I should also mention that the TBF/TBM Avenger torpedo bomber which was the staple torpedo bomber from late '42 until the end of the war began development in April 1940 with first flight in August 1941 with six of them first seeing action at Midway and completely replacing the Devastator by Guadalcanal. The F6F Hellcat started development in June 1941. The Thach Weave which was developed to overcome the weakness of the F4F Wildcat vis a vis the A6M Zero in maneuverability and turning radius was even developed pre-war by John S. Thach upon reading an intelligence bulletin dated September 11, 1941.

Correction: the book is Alternate Generals, edited by Harry Turtledove.

To clarify, I’m not expecting the US fleet to help Singapore in this scenario, only that it would be more likely that the pressure would be on the Philippines (and in this scenario I do think that most of the action and casualties for the US would take place in the Philippines) and most of the movements made by Japan would had been concentrated there thanks to the changed scenario. The other point is that I do think that commanders do react to the big picture and there is a lot in warfare that includes confidence, in the European theater most of the German troops had always been victorious before Barbarossa, and the early and almost complete victories in Russia allowed the Germans to continue with the big plan, that is, until reaching Leningrad and Moscow. The point here is that I do think that a big change of plans would had taken place when suddenly a key part of the Japanese scheme had failed spectacularly.

A commander that was considering retreating from the lower Malayan peninsula, even when everything was going their way, would IMHO had done so earlier before the British had surrendered when looking at the sudden change in plans and the need to get ready for the new reality that told them now that the predicted “running wild” for the first 6 months of the war was not in the cards.

What does that have to do with what I said, though?

Sorry if I’m missing something.

Pearl Harbor was part of a series of coordinated attacks, the US would not be doing a preemptive strike; IMO, and looking at the context of what was going on that day of infamy, it is clear to me that calling the destruction of the Japanese fleet close to Hawaii a “preemptive strike” is not accurate.

Whenever I see when of these counterfactual hypothetical threads, I always think of the old Saturday Night Live sketch, “What if Eleanor Roosevelt could fly?” where they had on an historian and an aeronautical engineer to discuss the implications. (And, which I am very disappointed to say I could not find in a YouTube search I just did.)