Days of Infamy: Invasion, Occupation, and Liberation of Hawaii (1941-1943)

Perhaps the Shinano could be completed. I actually don't know much about this ship. Do you have a picture of it? Perhaps it can still sail in this timeline?

 

To to Wikipedia if you want to learn about the Shinano. As to pictures, their is only one good picture of her. The Japanese kept her a secret for a long time.

 

One of only two known photos taken of her: the other was an aerial shot from an F-13 (B-29 rigged as a photo recon aircraft). The skipper of a tug took this shot with his personal camera during the carrier's short sea trials in Tokyo Bay a week before she was sunk. No aircraft ever flew from her deck, as she wasn't yet fully complete.

 

The Unryus were based on the Hiryu design and were easier to build. Six authorized OTL and three completed, and three surrendered incomplete at the end of the war. TTL, the Naval General Staff may go ahead and at least cancel Hull 111 (the fourth Yamato) and use her material to build the first two Unryus (Unryu and Amagi), and forego the hideous conversions of Ise and Hyuga into hybrid battleship/carriers.

 

I wonder about the intel implications of the fall of Hawaii. Kimmel and Short are known to have been captured—Rochefort and much of Station Hypo will also be either captured, killed in the defense of Pearl Harbor, or evacuated by submarine. Kimmel might leave himself to face Japanese punishment, but send his staff to California. The capture or destruction of American cryptanalysis personnel and documentation could make it harder to read Japanese codes later on.

 

I'd bet that subs extracted Rochefort and HYPO with their files, along with any of Kimmel's staff who knew about their work (Ed Layton, to name one). That was one secret that could not be allowed to fall into Japanese hands. VADM William S. Pye, Commander, Battle Force and who was to take over if anything happened to Kimmel, would also have been evacuated along with his staff.

 

In book two, their is a conversation between Fuchida, and another pilot about how the Americans knew the Zuikaku was returning to Hawiian waters just before the second invasion attempt, and we're able to torpedo her. They didn't believe the American were able to break ththe Japanese codes. So, I think that means Rochefort and his team were able to get out.

 

The fact that a sub was waiting for Zuikaku shows that the codebreakers were evacuated.

Data for the Unryus: https://en.wikipedia.org/wiki/Unryū-class_aircraft_carrier. Two canceled to enable Shinano work to continue, six units eventually authorized, three completed OTL. A seventh, from an improved class (Ikoma) was laid down and launched OTL, but never completed. Hulls 5008-15 from the Ikoma class were canceled before being laid down in 1943-44.

Likely Order of Battle (Ground) for the U.S. invasion of Oahu in June-July 1943:

I Amphibious Corps:

1st Marine Division

7th Infantry Division

27th Infantry Division

2nd Marine Division (reserve)

147th Regimental Combat Team

Corps Troops:

Several Army artillery battalions (155-mm and 8-inch Howitzer)

At least two Army tank battalions (Sherman)

At least one USMC Defense battalion (AAA

Several Army AAA battalions

Engineers: Both Army and Seabees.

 

So then, how many men do you think we're looking at in terms of a land invasion force? Any guess as to the strength of the Japanese on Oahu?

 

That's at least comparable to Operation FORAGER OTL in June-Jul '44. 127,000 men in 535 ships (carriers, battleships, cruisers, amphibs, plus escorts).

The planned Japanese assault on Oahu had they won at Midway had 3 divisions, a tank regiment, and an engineer regiment. I'm assuming the same thing here. Oahu's too big for one division to take-let alone garrison. Japanese OB would be the 2nd, 5th, and 53rd IDs, plus the tanks and engineers. Added would be the Special Naval Landing Force (3rd Kure), plus both Army and Navy air-base personnel, and the naval base personnel at both Honolulu Harbor and Pearl.

 

Thank you. Now, you make a good point point about Oahu being "too big" to garrison for one division. With that invasion force for the Japanese, what do you think would be the estimated numbers?

Also, I understand that Oahu is essentially the most important island in the Hawaiian chain, but do you think that the other islands would be occupied as well? Wouldn't the Japanese need to at least send occupying forces to these islands as well?

 

It's about 50,000 men not counting air and naval base personnel.

Genda makes a couple of observations about having garrisons on the other islands, but there's not much else in the books. My best guess is that Kauai, Maui, Molokai, and Lanai probably have garrisons from battalion to brigade size, with the Big Island of Hawaii probably having another division-sized force; a brigade around Hilo, one on the north coast, and another on the west coast-and none of these alone would keep U.S. forces from landing to retake all the islands. Remember that the B-17s and B-24s flew in from the West Coast-dropped their bombs on Oahu, then flew to Kauai-where, despite the garrison, it was possible to covertly build an airstrip large enough for the bombers to land-and get them resupplied-submarine activity was not just interdicting the Japanese supply lines, but also distracting the Japanese Navy's interisland patrols enough to get some ships into the other islands-some old WW I four-piper destroyers that would be considered expendable would do-to get the Seabees ashore on Kauai, and probably Marine Raiders onto the other islands.

 

That... kind of surprised me honestly lol You'd think the Japanese would be able to pick up on a US airfield so close to them.

 

It would be the last thing the Japanese would expect.

Carriers and battleships for the task force assigned to liberate Hawaii, June-July, 1943:

USS Hornet (CV-8)
USS Ranger (CV-4)
USS Wasp (CV-7)
USS Essex (CV-9)
USS Enterprise (CV-10)
USS Lexington (CV-16)
USS Bunker Hill (CV-17)
USS Saratoga (CV-18)

USS Independence (CVL-22)
USS Princeton (CVL-23)
USS Belleau Wood (CVL-24)
USS Cowpens (CVL-25)
USS Monterey (CVL-26)

Battleships (Escort for carriers, later augmenting the fire support group):

USS Washington (BB-56)
USS North Carolina (BB-55)
USS South Dakota (BB-57)
USS Indiana (BB-58)
USS Massachusetts (BB-59)

Old Battleships (Fire support group) Note: Colorado was at Bremerton NY, Washington, on 7 Dec 41, other three were in the Atlantic.

USS Colorado (BB-45)
USS Idaho (BB-42)
USS New Mexico (BB-40)
USS Mississippi (BB-41)

 

Nicely done here. You obviously thought long and hard about this. Any ideas as to the make up of the Japanese fleet around Hawaii at this time? Any chance of a "big guns" duel?

 

the wasp and ranger would be too small to be included with the main carrier force. but you could include them if they were committed to the assault force as air support assets for the landing force to allow a few more escort carriers to be used to ferry army fighters for land base use after the assault phase.

 

The Japanese force would be this:

Carrier Division 1 (Part): Akagi
Carrier Division 5: Shokaku, Zuikaku (Damaged-forced to offload air group and later scuttled at PH).
Battleship Division 11: Hiei, Kirishima
Cruiser Division 7: Mogami, Mikuma, Kumano, Suzuya
Destroyer Squadron 10: CL Nagara (Flag) with 9-12 DDs.

A Vice Admiral would be in command of a force this big. I'm assuming VADM Nobutake Kondo would have the command, flying his flag not from a carrier, but one of the battleships (he was a big-gun man). RADM Chuichi "King Kong" Hara (ComCarDiv 5 OTL 1941-2) would have been bumped up by this time to a higher command-he would probably be working on expansion of the carrier fleet along with VADM Jisaboru Ozawa, who did OTL command the carriers from late '42 on.

Once the two carriers are sunk-and there is also mention of a cruiser being abandoned and survivors rescued-the remaining ships offload the survivors in Hawaii, embark some high-profile personnel (like Zuikaku's air group commander and senior officer pilots), then they run for Midway-the closest friendly air cover. Kondo was no fool, but if he doesn't order withdrawal to Midway, Yamamoto will.

 

Of we're talking about the books, their was no mention of any battleships by the time the U.S. Navy returned in 1943. The only type of ship I remember reading about were heavy cruisers. As to flag officers, the one in the Japanese navy that was mentioned was Rear Admiral Takeo Kaku, who was Captain of the Akagi.

 

He wouldn't have been in command of the force. Something that big calls for a Vice-Admiral. Many IJN big ships (Battleships and some carriers) had a Rear Admiral as the skipper.

 

Two other islands that would have to be retaken before Hawaii's security is assured after liberation: Johnston and Palmyra. Once these two, along with French Frigate Shoals, Midway, and Wake are retaken, then serious planning can begin for the Central Pacific Offensive in 1944.