FWIW
A few of bits of info that might be useful in this discussion:
IJA and IJN fighter pilots were taught the concepts of pretty much all the basic combat maneuvers - including the preference to dive on, make a gunnery pass at the enemy fighter, then regain altitude again (ie boom-and-zoom) - before the war with the US and UK began. This tactic was used quite often against the Chinese, and against the various foreign squadrons like the AVG. The Japanese mostly used the 3-plane formation with a leader and 2 wingmen, however they were somewhat flexible and sometimes used 2 pairs depending on whether the number allowed one tactic or another.
As the war progressed IJA pilots (in particular) were taught to attack US bombers from the front if possible and/or shoot for the cockpit if possible, where 2x 7.7mm/.303 cal or 2x 12.7mm or a combination thereof could be quite effective. Both IJA and IJN fighter pilots were taught to close to as close a range as practical before opening fire. Also, a 3-plane section would usually all attack the same bomber in a short, slightly offset line astern format, increasing the chance of hits on the target and (hopefully) not allowing the bomber gunners time to switch targets while maintaining a near continuous stream of fire.
NOTE Before anyone pooh-poohs the above statements, this is known doctrine from training manuals and post-war interviews (including debriefs by US intel agencies) of Japanese pilots. I also find it interesting that so many people seem to think that when pilots like Boelcke, Galland, etc, say some of the same things it is accepted as gospel, and lauded as so great and explains so much of their success, but when it is said by/about the Japanese pilots it is ignored/discounted as a part of their success.
Yes, to add to this - the IJN in particular focused on 'boom and zoom' tactics, and only resorted to turn-fighting when the situation 'devolved'.
The Japanese Army Air Force used a captured B-17 to practice their head-on attack system in 1942, there is a mention of this in Bloody Shambles, I'll see if I can find it. It is notable that the newer mark B-17s and B-24s with the chin / nose turrets somewhat derailed this tactic when they arrived in Theater.
re range and cruise speeds of the Japanese fighter aircraft
Both the Ki-43-II and A6M2/3/5 were capable of sustained 300 mph TAS rich-mixture cruise (though obviously this decreased their range) and their normal minimum cruise was around 250-280 mph TAS when anywhere they figured they might encounter enemy aircraft. The only time they cruised at particular low speeds was if they were deploying (reinforcing in UK terms) over long distances, on CAP duty (when loiter was really important), or on the return leg to their base or carrier. (NOTE that in the PTO the standard USN/USAAF and RAF/FAA flight profiles were similar to the IJA/IJN in most cases, with low speeds being used for CAP loiter and the return leg flown at best V/weak-mixture cruise for range.) The A6M2 with its centerline DT could cover well over 1000 miles at 250 MPH TAS at 15,000 ft with reserves for combat and loiter. The Ki-43 had similar range when using drop tanks. 280 mph TAS was the approximate maximum weak mixture cruise for both aircraft. I am not sure about the Ki-43, but the A6M2/3 could sustain max speed for 1/2 hour or more without overheating.
Very interesting, thanks for the detail there.
These ranges are enough to escort their bombers for most missions, and there are quite a few mentions of A6Ms escorting Betty's and such at altitudes of 20,000 ft or higher. Yes, there were some bombing missions where the ranges were beyond the fighter's practical range, but this was true for the Allies as well. The Allied bombers flew at altitudes higher than 15,000-20,000 ft in the ETO, so it would be considerably more problematic for the early-war Japanese fighters to escort/attack them at such high altitudes. Over Japan, the Ki-43 and A6M both had the altitude capability, but their speed at 25,000-30,000 ft meant that they could usually only make one head-on pass against the B-29s, while against B-17s and B-24s they could usually do 2 or more passes depending on the altitude, formation, etc.
The big limiting factor on altitude was what bombers could see. In certain Theaters, fog, clouds, rainstorms etc. obscured the ground and really prevented accurate high altitude bombing. The nature of the target could affect this a lot as well. Major ports and airfields, refineries or factories are relatively hard to hide, but ships, AAA and artillery guns, military units, small anchorages, and smaller military installations are much easier to conceal and can't easily be hit from high altitude.
The worst Theater for visibility was the Aleutians and North Pacific, arguably. After that the South Pacific, New Guinea basically had a minor hurricane every single day somewhere around the coast, and dozens of thunderstorms broke out just about everywhere. Solomons weren't much different. Burma varied somewhat by season (operations are basically winter and spring- it rains steadily through the Monsoon season from May to October severely limiting air activity) but was often concealed by cloud cover and everything was jungle, making it hard to spot targets. Mediterranean Theater may have been the best in this sense with the clearest skies, making heavy bomber raids against Axis airfields, once these became possible, particularly devastating, though smaller tactical and operational targets were still very hard to pinpoint and really needed to be targeted by dive bombers, low altitude bomber / strafers, or fighter-bombers. NW Europe was of course also often cloudy or cloud-covered, but was clear enough, often enough, to at least allow Strategic bombing of major industrial targets like factories, or barring that, entire cities. Once the tactical war started though in Italy and then Normandy etc., once again identifying targets required getting low. Russia and Eastern Europe were also frequently covered by a lower altitude cloud layer, depending on the season.
All of these factors meant that bombers didn't usually have the luxury of bombing from 25,000+ feet even if they had the capability. Quite often a low cloud layer, and / or the simple necessity to fly close to the target in order to see and identify it required bombers to operate much lower, 10-15,000 ft for level bombers, often right down to Sea Level for dive bombers, fighter-bombers, and strafers / low-level bombers. This in turn meant that the fighters were often engaged at low to medium altitude in pretty much every Theater except during the Strategic bombing campaigns late in the war.
re claimed kill ratios of the USAAF and USN
Despite what appear to be claims to the contrary, the USN did not make any in-depth attempt to validate kills by its pilots. This makes sense to very large degree for several reasons. One reason is simply because it was not important in the grand scheme of things. Having an ace was good for morale, having a bunch of aces was even better. It was also impractical to arrive at accurate numbers without discounting their pilot's claims - and that would be bad for morale. And what purpose would this serve in the eyes of the higher ups - the war was over, the Allies had won. I am not saying that the higher-ups did not think it important at all, just that there were much more important things to deal with.
The actual kill numbers accepted were arrived at by interviewing the squadron commanders (or similar) and asking them if there was any reason to believe any of the claims were not valid. Sometimes the questions would be extended to other squadron mates, or other personnel who were t the fight. What else were they going to do? Send out search parties to scour every square mile of every island in the PTO? Send divers to the bottom of the ocean where the action took place to look for wreckage of aircraft, write down the aircraft serial number, then match the number to particular Japanese and Allied squadrons, then to a particular mission and to a missing Japanese pilot? As has been pointed out in this discussion (and in others on this forum and other forums) when the actual loss of aircraft or pilot in the squadron rosters do not match the enemy claims (eg the supposedly shot down aircraft and pilot are recorded as returned home after the mission), and this sort of thing happens over and over again, there is no rational argument than can be made that the kill claim relative to the actual kill:loss ratio is accurate. This has nothing to do with any attempts at honesty, or deceit on the part of the pilots or the higher-ups, only a lack of numerical accuracy due to one factor or another in the fog of war.
I agree but would push back on this slightly - commanders and planners did want to know how many enemy aircraft were shot down. It's fine to credit pilots with victories, (and the JAAF became particularly lax about this, probably for morale reasons, especially later in the war) but for planning and allocation of reinforcements and resources it helps a lot to know. The Soviets at one point were requiring recovery of aircraft identity plates to verify claims. US, UK and German units were (eventually) using gun cameras (not sure if Italian and Japanese did this). They often had specific criteria which could be fairly strict to validate a 'confirmed' vs a 'probable' or a 'damaged'. But even with these measures in place, overclaiming was a constant. Ratios seemed to vary from around 2-1 to as high as 10-1, tending to be higher in bigger battles, and also depending on the experience of the unit and how strict the criteria were.
The Germans prosecuted some pilots for fake claims, the Japanese were at least suspicious of some pilots in this regard as well. Historians debate it, but intentional overclaiming seems to have been fairly rare.
Incidentally, despite stories to the contrary, the Japanese did not destroy any significant number of their squadron records, though it did happen when the Japanese forces were forced to retreat and there was no time or load carrying ability for transport. A significant number of squadron records were lost due to sinking of carriers and destruction of the base installations holding the records. Most such records were confiscated by the Allies in a similar manner to what happened in Europe. Some records were destroyed by order of the Allies after the war. Some of this was due to the attempt at demilitarization of the Japanese society, in a similar manner to the demilitarization/deNazification of Germany, and some of it was due to operational studies, and some of this was in order to control the narrative after the war.
As mentioned up-thread, the accounting in the ETO and to a degree the MTO was a bit easier due to most of the action being more localized and over land. Yet even in the ETO, as time marches on and more and more records are found and analyzed, we still find evidence in the squadron records that seriously change the kill:loss claims. Again, this has nothing to do with any attempt at honesty or deceit on the part of the pilots or higher-ups, only a lack of numerical accuracy due to one factor or another in the fog of war. The population density in Europe means that most of the crashed aircraft that crashed on land and were unaccounted for have been found, though 1 or 2 are still found each year. In the vast open ocean and remote islands and jungles of the PTO and CBI there are still 1 or 2 found each year.
Note that most of the confiscated records were returned at a later date, when and if depending on the nature and perceived importance. Some are still classified and have not been released due to their declassification "not being in the [US] national interest".
They do have archives of Japanese records which are mentioned as the sources by Shores, Claringbould etc. and can in fact now be searched fairly easily with the help of LLM software tools etc. There are some gaps as you note, but they seem to be substantially complete for most units and for long periods of time.
re the G loads of Japanese aircraft and WWII aircraft in general
Japanese pre- and early-war fighters (and I think medium bombers as well) were designed along the lines of the British in terms of structural strength, though with lighter operational weights in general. Their Specifications contained similar requirements in many cases, and used very similar terms, expressions, and values,
The aircraft with the best sustained G in WWII were only capable of a little over 3G without loss of speed or altitude. Some of the early-war aircraft that could do this were the Spitfire, Bf109F, Ki-43-II, and the A6M2/3.
bleh
Even pulling G and losing altitude could be recovered, via dive and zoom climb, maneuvers like what came later to be called 'Low Yo Yo' etc. Dogfights tended to spiral down to the ground one way or another eventually, and that is when the life or death race often began.
but I know which plane I would want to fly over the Bay of Biscay or the Med 
