More on the Japanese Midway Games

Never being one to leave things alone I want to say more about the last two sentences from the quote from [1] in the last post.

 Still, Admiral Ukagi failed to address the issue the loss of his carriers in the wargame should have brought up - what if the American's get in the first hit? Would we have enough strength to win anyway?

We can answer this at least partially by assuming that The Japanese believed that a deck load strike from a fleet carrier could mission kill or sink two carriers. This is what Wayne Hughes, page 100 [2], tells us was the belief of US carrier forces at the time. This is consistent with the hit rate achieved in the Indian Ocean raid by the Nagumo force, and probably consistent with initial inflated reports of the results of the 5th Carrier Division attacks at the Coral Sea.
The Japanese estimated that the Americans had two fleet carriers available to defend Midway, thus if the Japanese credited the Americans with the same level of performance they credited themselves with, a first strike from the Americans would neutralist four carriers. If this occurred before the Nagumo force launched a counter strike, in the initial games this would have left the Japanese with two operational carriers, sufficient to eliminate the US carrier force since the Nagumo force in those games had the full six fleet carriers. If the Nagumo force had only four carriers, as in the second set of games and on the day, then it would have been mission killed (and with subsequent American strikes probably all the Japanese carriers would have been sunk).

Now it is likely that the Japanese did not credit the Americans with comparable capability as they thought they themselves had. So now assume that the Japanese credited the Americans with the ability to mission kill or sink a single carrier with a deck load strike. Then the two American carriers, with a first strike before the Japanese had the chance to launch, would have neutralised two of the Nagumo force's carriers, leaving sufficient forces to eliminate the American carriers with a counter strike. Note, according to Hughes [2] this is the level of effectiveness displayed (more-or-less) by both carrier forces in the battles of 1942. While in the main games of the second set (24/25th May) when the American sortied the two forces exchanged strikes the level of Japanese casualties incurred are consistent with this assessment.

It seems that the Japanese were well aware that if the Americans got lucky the game would be up, and orders were issued to minimise the chance of such luck (pages 67-8 of [3]). On the day the game was up because the Americans did get lucky, and they had three rather than two carriers available.

With an average amount of luck on both sides, on the day we might expect an initial exchange of strikes with the result of three US carriers mission killed or sunk, and the same number of Japanese carriers mission killed or sunk. Then the Japanese would have been able to follow up and probably sink any US carriers still afloat from their remaining operational carrier. Since after the first strikes there are no remaining US carriers the Japanese have the chance to save any of their carriers that were not sunk.

It should be pointed out that even a loss of two carriers by the Nagumo force as a price for the elimination of the American carriers might have been too high a price for the Japanese. The Midway campaign was just a part of the Japanese plan for the second stage of the Pacific war, and the loss of two carriers might have been sufficient to compromise the viability of the subsequent operations in the South Pacific and against Johnston and the Hawaiian islands.

References
1. Caffrey M., History of Wargames:Toward a History Based Doctrine for Wargaming , Jan 2000, http://www.strategypage.com/articles/default.asp?target=WARGHIS2.htm&reader=long
2. Hughes W. P., Fleet Tactics and Coastal Combat, Naval Institute Press, 2000
3. Parshall, J.B., Tully A.P, Shattered Sword, Potomac Books 2005