Berkut >> sorry but I can't agree with you on most you wrote:
"A point made in FITS is that the Japanese military, and especially the IJN pilots had a LOT of influence on the design of the Zero."
-well that is true only up to some point. When designing A6N fighter there were prolongate and quit "hot" discusions about its desingn. In fact navy changed specifications at last once during proces which nearly lead to failure of whole project. One group of pilots demanded specifications of aircraft roughly of A5N qualities -short range, small calibre MG, wery manourable, speed unimportant. Another group argued for longer range, strong armament, fast, maneurability not important. They actualy argued that lack of agility can by ofset by pilot skill.
Those discusions lasted few days without final result, neighter part be able to win. Situation was finaly resolved by Horikoshi himself when his design met both sides requirements and even exceded reguirements in some fields.
Another fact you should notice is that still before war both navy and army started to design planes of "totaly diferent bread". Those were army Ki-44 and navy J2N, J2N by same designer as Zero by the way.
" Now, what make a fighter better than some other fighter?"
-way you use it of course. In general for ww2 fighters that meant: to use strong points of your plane while succesfuly negate those of your oponents.
"What if it is the case that Fighter A is MUCH better than fighter B, but only if both sides fight in a certain manner? Of course, I am referring to the "turning fight" that the Zero is so well known for."
No, Zero was "found" to be good not only at turns but for been good in any maneuers in general, including vertical ones. Especialy at lower speeds. It was also wery good climber and J. pilots ofthen used its climbing ability to escape from danger early in war. Climb is also important since it lets you gain altitude in combat and altitude meant initiative as a rule in those times.
Speaking about fying characteristics its weaknes was only in controls became hard at higher speeds and max. diving speed been lower relative to its oponents.
"The thing that I think amde the Zero so successful early on is that when it comes to doctrine, it was designed to fight well in what I would call a "natural" style of fighting."
But that was general stile of fighting in all armies in those times. Germans been firsth to develop something else only at the begining of Barbarosa. They started to use something what was later know as "energy fighting". There was AVG group in China but they were using simple hit and run tactic, not realy energy fighting.
Again, what realy made Zero so good early on is that it was good design + Japanese use it well + Alies unable to counter.
Japanese had battle experienced pilots, battle experienced leaders, much better morale, better weapons and most important superior tactic. Because of their experience from China and Chalkin Gol they used tactic which alied only had to learn. That included superior coordination between air units as well as air and land and air and naval units. Conception of gaining air control over whole operational area, bomber escorting, force concentration and so on.
Only way hove early alied planes could have chance to win against Zero was to start fight from higher altitude and use this advantage quickly to get kill.
" A Zero is a lot better than a P-40 in a turning fight, but a P-40 is equal or even better if it can avoid that kind of fight."
P-40 is better only in dive and is slightly faster in level flight -which it cant use in combat since it have worse acceleration by the way. And of course it is better protected -which alone is pure defensive atribute. In all other important aspect it is inferior to Zero: climb, wertical maneuvers, horizontal maneuvers, roll, acceleration, power loading, wing loading, range. You can discuse which have better armament, I think both are +- equal in this.
What Alies needed to win was better plane. Whithout it they could not use any doctrine for their good.
"You cannot force someone to engage in a turning fight if they do not want to."
Of course you can: firsth of all, any kind of fighter combat require some kind of "turn", been it in horizontal or vertical plane. Flying strait you gona hit nobody.
But lets take example when two aircraft engage and one is good energi fighter good on vertical and another is better in horizontal turns: If second succes to engage firsth in prolongate fight, then planes slowly start to loose speed/altitude and at some point firsth one have to abandon vertical since it lack energi for that.
Of course there is always option to end fight if you are better in diving than your oponent -but you dont gona win by leaving. In some cases it also mean defeat, for example when you are escorting or flying cover.
That is the way hove Hurricanes could succesfuly engage Bf-109 in battle of Britain by the way.
-just my few ideas and sorry if it look bit confrontating, it wasn't meant as such
