The Japanese Plan
Admiral Yamamoto has been planning for months a decisive blow against the American Pacific Fleet at the start of the war. He feels that in a single blow the First Air Fleet can eliminate at least 4 of the American battleships and clear the way for operations aimed at the Southern Resource Area. With proper planning and a bit of luck, all 8 of the battleships can be at least damaged enough to knock them out for some weeks, and with luck one or two or even more of the American carriers will be in port and they can be destroyed as well.
This will require eliminating the American ability to resist the strike by removing their fighters from the equation, as well as eliminating any counterstrike ability. A report from Takeo Yoskikawa regarding the embarrassment of the US Army in recent war games as well as the report that US Navy conducted a simulated strike against the Army airfields and fleet base poses a worry to Yamamoto, who thinks that possibly the Americans may anticipate his plan. Yamamoto decides to revise his plan somewhat, and more importantly, decides that as he is seeking Kantai Kessen (the decisive battle) with the Americans in their home waters,it would best be lead by him in person. The change takes several days to get approved by Admiral of the Fleet Nagano but in the end Nagano accepts the decision. The battleships Nagato and Mutsu replace the two fast battleships assigned to southern operations and to support them Yamamoto adds 4 more destroyers and 4 more fleet oilers to the Striking Force. Yamamoto also decides that to support future attacks against the American fleet base, Midway Island should be seized as well. A proposed landing in the Gilbert Islands is canceled, and those forces assigned to deal with the weakly defended US base at Guam, while the South Seas Detachment and the ships assigned to it are pulled from the Guam operation and instead will follow behind the Striking Force and after the raid on Pearl Harbor the carrier fleet will support the seizure of this base, which is good location to stage seaplanes from the Mandates to spy and harass Hawaii, as well as offering a refueling facility for submarines to patrol east of Hawaii and harass naval traffic from the US West Coast.
Operation AI
The plan has as its essentials the following tasks
1. Eliminate the threat of American aviation to the air strikes on the American fleet as well as its ability to launch coordinated strikes against the Striking Force
2. Eliminate the capability of the US Pacific Fleet to interfere with Japanese operations in the Southern Resource Area by sinking or severely damaging at least 4 battleships, and inflicting serious damage on the remainder.
3. Bring to battle American carriers and their escorts if they are not in port, or eliminate them as secondary targets if they are in port. This will remove American ability to harass Japanese operations and garrisons in the Central Pacific.
(authors note: With the exception of bringing to battle the American carriers if they are not in port, this was the historical Japanese plan. Note that nowhere is there any mention of attacking the repair facilities or fuel reserves at the base. The whole focus of the operation was to attack the FLEET, not the base except as incidental to hitting warships in drydock and of course the airfields. A change in the operational priorities of the Japanese Navy requires a bigger point of departure than I am willing to make)
Japanese Forces assigned Operation AI
Kido Butai (First Air Fleet) (Striking Force)
Carriers Akagi, Kaga, Soryu, Hiryu, Shokaku, Zuikaku, battleships Hiei (fleet flag: Yamamoto), Haruna, Kongo, Kirishima, CA Tone, Chikuma, CL Abukuma, 14 destroyers, 12 fleet oilers, 414 combat aircraft (54 Zero fighters for fleet defense, 354 for striking force including 81 fighters, 143 B5N Kate torpedo/level bombers, 135 D3A Val dive bombers) plus 20 float planes for scouting
6th Fleet (submarines)
31 fleet submarines plus 5 special attack (midget) submarines
Midway Island Assault Force
CA Aoba, Furutaka, Kako, Kinugasa, 4 destroyers, 2 gunboats, 6 submarine chasers, 1 seaplane tender, 2 tenders, 9 transports, South Sea Force (4,886 troops