Originally posted by Viper61
1) The most major reason was Yamamoto dividing his fleet into thirds (going against American sea power guru Mahan's doctorine of "never divide your fleet"). one third was sent to strike Midway, one third steamed north as a distraction, and the last third stayed put (again the arrogance of Yamamoto mentioned before in this discussion).
I disagree with this as the "most major" reason. While it's true that the Japanese divided their operation into three arcs, the BULK of their fleet was at Midway, not a mere third. Of the eight Japanese carriers (four heavy, four light), all four heavies - the AKAGI, KAGA, SORYU, and HIRYU - were directly involved in the Midway arc of the operation, along with two battleships and most of the cruiser/destroyer screen. Two light carriers went to the Aleutians with a couple of battleships and cruisers, and several destroyers. The light carrier ZUIHO was with the Main Battle Fleet consisting of the remainder of the battleships, 700 miles behind the heavy carriers. The last light carrier was carrying out small strikes in New Guinea (often not even considered part of the operation en totale).
There may have been 3 thrusts of action, but 80% of the Japanese fleet was at Midway proper. While dividing the attack thusly certainly had an impact, it was clearly not the primary reason for the Japanese defeat.
2) The US had broken most of the the Japanese code (also as mentioned before)
This is UNQUESTIONABLY the primary reason. The US fleet probably would not have gone North, even without knowing the Japanese plans, but it would have played into Yammamoto's scheme of arriving at Midway AFTER the island had been secured. Yammamoto would hav ealso brought up his Main Battle Fleet and sought surface engagements. The combination of four heavy and one light carriers, land-based air power, and battleships would have likely decimated the US carriers (remember, the US fleet had no battleships along). Knowledge of the plans, and establishing a counter-ambush (element of surprise) is the single most important aspect of the Battle of Midway.
3) US had superior aircraft and pilots.
No way. The A6M Zero outperformed the F4F Wildcat in every statisitcal category except diving speed, though the Wildcat was more rugged and better-armed. The B5N Kate was markedly superior to the obsolete TBD Devastator (and carried the best torpedo in the world in the Type 91 Long Lance). The only parity was in dive bombers, where the SBD Dauntless was generally a slightly better aircraft than the D3A Val.
The Japanese had a clear experience advantage, though US flight and fight tactics were noticeably better than evena month earlier at Coral Sea. Of course, the extreme range that the US planes had to fly so mixed up the flight coordination that the sacrifice of the Devastators was necessary to allow the Dauntlesses to make their deadly attacks almost unopposed.
the superior firepower and armor of the slower US Corairs and Mustangs beat the faster more maneuverable, but significantly less armed and armored Zeros.
Corsairs and Mustangs didn't exist as combattants in the Pacific yet. Perhaps you meant Wildcats? At any rate, the Corsair and Mustang were both faster than their Japanese counterparts later in the war (the former was one fo the fastest piston-engined fighters ever). The Mustang was more maneuverable as well.
