Grywolf1;
There are a great many reasons why the USN could, and the IJN could not.
The USN needed USS Yorktown (CV-5) to go. Nimitz was prepared to send Spruance, with USS Enterprise (CV-6) and USS Hornet (CV-8), alone, but he did not what to. Thus, the USN was inspired to get Yorktown repaired.
Second, the air group change on Yorktown was a planned event. Yorktown's Air Group had been in action with but one brief respite, since January. Aircrew casualties had been significant, but not terrible. None the less, the folks were tired and it was easier to swap in Saratoga's three fresh squadrons that had been at Pearl since January just itching to got to sea. Thus, VT-3 replaced VT-5, VB-3 replaced VS-5, and VF-3 replaced VF-42. However, of the three new squadrons, VF-3 had been striped of most of its pilots so, in reality, the CO, "Jimmy" Thach had to "acquire" 16 of VF-42s pilots to outfit his squadron. As VS-3 was actually on the west coast with Saratoga, one of the two SBD squadrons on Yorktown had to stay, and VB-5 got the call – after which it was unofficially renamed VS-5 which caused so much confusion at Pearl in the next two weeks that it took all kinds of paperwork and orders to fix the mess! However, the squadrons were veteran squadrons that, other than being new to Yorktown, were ready for their job. So, in reality, it was not really a "scratch" group. 2 1/2 squadrons were veterans that had been practicing together for months, and 1 1/2 were combat veterans from Yorktown.
In the USN, the switch was easy because the squadron integrally contained all the necessary elements (aircraft, aircrew, and maintenance personnel).
Conversely, the IJN squadrons contained the aircrew and planes only. The maintenance personnel belonged to the ship. Further, the ships squadrons were not truly independent units. Rather, they were part of the carrier division's formation. Thus, the presence of both elements of the division was necessary to train personnel properly.
When the 5th Carrier Division left the Coral Sea Shokaku was gravely hurt, and it carried but 10 unoperational aircraft and virtually no aircrew. Zuikaku, unhurt, carried 25 fighters and 27 strike planes (less than 75% of what she carried and less than 40% of what the division started the battle with). However, of the 27 strike planes, only 12 were either operational or repairable on board. The others were "hors de combat" from .50 caliber MG hits in structural components that required a full factory overhaul. Thus, the ship only had 12 aircraft ready to carry the fight to the enemy when she got to Japan.
On return to Japan, as in all naval services, many personnel were scheduled to move to different assignments. This included many of the veteran aircrew of the two carriers that arrived with Zuikaku. They were going to other carrier units or training establishments. The folks they were replacing had already moved on. Their transfers were, effectively, non-negotiable.
Further, what remained needed to go ashore to acquire, new aircraft and replacement personnel. With a number of Buntai, Chutai and Shotai leaders gone, promotions and transfers to these leadership positions were critical. After the personnel and aircraft arrived, the entire divisional air group needed training time. All of this could have been handled.
However, it was the need for new aircraft, that threw to proverbial "wrench" into the machinery – there wasn't any. Japan had gone to war having already stopped production of the B5N2 attack plane (in preparation for commencing production of the replacement B6N which didn't come out until 1944!) and preparing the do the same in one of two plants making the D3A1 (in preparation for starting production on its replacement, the D3A2). BY early 1942, even with the amazingly light losses in the war to date, the IJN was simply running out of combat strike planes. Heck, even production of the A6M2, which was being produced in significantly higher numbers, simply could not keep abreast of the need for it on the carriers and in the elite land-based Kokutais.
After stripping all the new aircraft available in preparation for Operation MI, several units involved under strength. The 6th Ku, which was to be carried, by the various carriers involved, to Midway for the new bases defense was going with only 33 of its authorized 36 fighter planes and pilots, and 50% of those pilots were only Class C (Class A being the best and Class D the worst). Junyo only managed to get 12 fighter pilots (including several Class C boys) and but 6 aircraft. She would have to utilize the 12 6th Ku aircraft she was transporting, and some of the pilots, to make up the difference. Ryujo was still using many under powered B5N1 attack planes as there were not enough B5N2 models, and she had only just replaced the A5M4 fighter planes she had been using since the war started with but 12 new A6M2s. Zuiho was also operating all B5N1 models, she had just got new A6M2s, and most of her aircrew were Class C as well. Further, none of the carriers had any of the spare aircraft and aircrew that they were authorized to carry. Then there was Hosho, which was only carrying a single Chutai of the outmoded biplane attack planes the B5N1 had replaced (her elevators could not handle the new aircraft) and no fighters, which was only leaving port to provide ASW protection for the main force battleships.
Effectively Japan had simply run out of the ability to replace its losses while struggling get the new carriers into service and to increase the size of the land-based air arm necessary to defend the new Pacific Rim bases.
Of course, all of this was really wasn't important because, as everyone in the IJN knew, the overwhelming force already deployed in the MI operation would simply roll over the astonished and incapable American's as Admiral Yamamoto had forecast. While the men on the new Zuikaku certainly would have liked to have been participants in the war's crowning battle, they were not the "first-team" anyway and just weren't needed to crush the enemy.
Thus, the long of the short of it is the American's "need to get it done" approach to springing their trap was pursed at every level by a commander in chief who was willing to risk everything because he believed in his codebreakers, his carrier commander, and his carriers air staff's ability to utilize their highly trained aircrew to win a battle the enemy was not expecting. Conversely, the Japanese attitude was incredibly lackadaisical because they "knew" that the results had already been "ordained on high" and they giving the Americans a chance to "play out their losing hand".
Hope this hepls.
Mark E. Horan
Oops.