lwd, thanks for your quick response,

Getting the invasion force you have suggested anywhere near Hawaii without being detected is highly problematic. Let's look at the problems:

1) The transports have to leave well in advance of the fleet or the whole fleet has to travel at the transport speeds. This has a number of implications.

Historically the KB travelled at 14 knots but averaged only 11 due too refueling needs. My 1LW has 9 ships, each capable of 20+ knots. I see no problem.

One of the most important is it leaves a lot more time for the force to be discovered.

By who (whom ?) ? There was no one out in the northern Pacific at that time of year to see them and in the OTL Nagumo had orders to quickly sink anyone that stumbled across his strikeforce. I see no problem.

It's also a much bigger target as far as observation is concerned.

What difference does size make when there is no one else out there to see them ? I see no problem.

2) When the battle fleet "dissapears" warning bells are going to be going off all over the place. The longer they are at sea the harder the allies are going to be looking for them.

If you would re-read my previuos posting you will see that my ATL Japanese will attempt to make the Allies believe that the CF is engaged in gunnery training in the Bonin Islands. I see no problem.

3) Then there's the problem of fuel usage. Japan does have enough fuel for this op but it's going to require most of their tankers and many of the ships will have to refuel at sea some several times.

My previous posting indicates that 12 instead of 8 tankers would need to be converted, in secret, to UWR capability. I see no problem.

4) In addition to their being extra searches everyone is going to be quite a bit more alert. One of the things that helped at PH was that the impression was that sabotage was the main thing they had to worry about. If the Japanese battle fleet has been unaccounted for for weeks that perception is very likely to change.

Bonin Islands. I see no problem.

5) Consider also the code breaking situation. The Japanese naval code had been compromised but they changed it just before the PH op. If they change it according to RL then there's a very good chance some details are derived due to the op getting underway weeks earlier. If on the otherhand they change just before the op starts there is a chance that the US will have broken the new code at least to some extent before the strike and gotten some valuable info that way.

Historically the Japanese removed transmitter keys and shoved folded paper between the contacts to ensure that there were no accidental KB radio transmissions during the approach to Oahu. My Hawaii invasion force would do the same.

With the added bonus of having the American approved Tatuta Maru scouting out ahead. Any radio signal "leak" from the Hawaii invasion group would just be atributed, by any listening RDF Americans, as yet another TM origin civilian radio message.

The absence of the battle fleet will likely spur efforts in this regard.

Not absent. At gunnery practise in the Bonin Islands.

As for the Japanese practicing landings in China. How long did it take them to get forces ashore? My understanding is Sakai was amazed at how fast the US was doing it at Gaudacanal. At least in the copy of the Caiden book it is stated he thought that the US was doing this much faster than the Japanese.

By the time of Guadalacanal the Americans were using Higgens boats and alligators to bring "everything but the kitchen sink" lavish levels of supply, ashore. OTOH my ATL Japanese invaders would be light infantry on a "shoestring" logistics plan of living off of the land on Oahu.

The practice landings in China would also not have been in heavy surf, in areas with coral reefs, vs land, sea, and air opposition.

They were hardly practise landings. Combat was often entered within a mile or two of the surfline crossed.

Please remember that Oahu's peacetime civilian radfio stations broadcast 6 times a day marine weather forcasts for the benefit of the 400+ Oahu fishing sampan fleet. My ATL Hawaii invasion force would also be listening to those forcasts as they neared Oahu so as to be able to choose landing beaches not hampered by high surf.

I'm pretty sure the US had at least a small armored force on Hawaii as

JUst a single company of 12 early versions of the M5 Stewart light tank, easily stopped by the 6x47mm horse drawn AT guns that were a vital part of a Japanese regiments's TO&E.

well as numerous coastal batteries (covering the likely invasion beaches).

There were indeed lots of Coastal Atrtillery Corps (CAC) shore batteries on Oahu but they were mostly placed to cover Mamala Bay to the SW of Honolulu and the Pearl Harbor entrance channel. The 1940 Americans had budgeted to build shore batteries to cover Kaneohe Bay but by Dec.7'41 none had been yet built.

In addition the US Army defenders of Oahu had several 8" railway guns and a host of 155mm GPF artillery pieces emplaced for shore defence work but they were habitually returned to their inland depots over the weekend. General Short was afraid of sabotage, remember. As I'm sure that you know, Dec.7'41 was a Sunday.

I certainly wouldn't want to try a night invasion in this situation and or bring my transports in range of shore batteries.

Trying it on Oahu at any time other than night would be virtually suicidal.

If given a free hand Yamamoto wouldn't have tried it.

I agree completely since Yamamoto knew that Japan couldn't possibly win a Long War against an industrial giant like the US. He only insisted on hitting Pearl Harbor when it became apparent that his political masters were insisting on a Pacific War with America.

My ATL scenario supposes that he had been given a "free hand" to do his best to force a Short War with the Americans rather than a Long one.

If he had elected to try it given his (and Japan's) proclivity for overly complex plans that tended to underestimate their opponents doing something stupid I wouldn't give them a very good chance of success.

You are certainly entitled to your own opinion but I intend to try to change that here.