Originally posted by joel rauber
"It is clear in the book that Frank has gotten a hold of a map of Australia. It does cut the major supply route from the US to Australia."
You can hand Noumea and Fiji to the Japs and convoys can be routed further south - it doesn't cut the supply line, it just stretches it and the allies had enough merchant shipping to do it.
You can even give Japan New Zealand and still ship to Aust from the US east coast to the Aust west coast.
There is no credible possibility where the IJN can blockade Aust.
" Cutting such supply routes would be a major concern for US and Australia and 'was a major concern'. "
Which doesn't make it a realistic concern, we have the benefit of knowing what supplies, shipping etc Japan had and what other commitments they had - in early WW2 they were guessing and had to guess on the pessimistic side for safety.
"Of course it would threaten Australia, if it was no threat then a Japanese thrust into the south pacific would not be a concern to the allied effort; its a matter of historical record that it was a major concern. "
Covered above.
"I'm just disputing the idea that under certain plausible hypotheticals that Japan could not blockade Australia, and by blockade I mean cutting the major supply route from the US. Naturally this does not imply a full blockade in the sense of no shipping what-so-ever reaching Australia. Perhaps I should've said 'limited blockade' or 'cutting of major supply routes' (not all supply routes, of course) "
I'm sorry but the above is just not sensible - blockade means blockade, not 'just cutting off Aust from the US' - keeping Americans out but letting a Brit armoured div in, is not very productive and you have not shown how siezing part of the south pac would provide the extra fuel tankers needed to support IJN ops in the southern ocean (holding a few islands is not the same as being able to operate well south of them) - that where the allies can route convoys if they need to and there is nothing Japan can do about it.
"I assume that a successful South Pacific thrust would make a limited N. Australia invasion more plausible. "
Less plausible as it leaves you with less troops, supply and way less shipping to work with.
"Would you grant that if Midway was reversed, that it is plausible that Port Moresby could be taken? "
I seriously doubt it, the Japanese logistics were too poor and trying to come into Moresby by sea would have exposed the Japanese to contested landings, something they were very bad at.
"Why would a limited N. Australia operation require 12 divisions?"
You would probably need to ask the IJA who felt that 12 Divs was the bare minimum, however given that Aust could assemble 8 Divs by Mid 42 (plus various US units and a Brit Armoured Div promised in case of invasion) it is quite clear that 12 Divs is insufficient - throw in the material superiority of the Aust Divs and a 12 Div limited invasion is in lots of trouble.
" And whether or not the divisions could be spared is debatable anyway. Japan did not have a shortage of rifle divisions. They fielded more than the US did in WWII."
As I recall the US was not invading China as a principal war aim, which rather significantly lowers the amount of rifle divs they needed, Japan on the other hand was trying to take China, hold Malaya/Singapore, take Burma/India, hold Borneo/Indonesia, hold the Phillipines, take New Guinea, take Guadalcanal plus Japanese Garrisons, Korea etc - when you have lots of tasks, you can have lots of men and still be spread a little thin - they could not spare 12 Divs.
" Of course, you'd be correct to point out that you also have to have the shipping for the divisions as well. I don't consider a limited N. Australian operation as requiring 12 divisions or anything close to that. I stress the word 'limited'. "
THe IJN stressed the word limited too and the IJA (who would have to do it) felt that 12 Divs would not be enough - how many Divs would you take up against 8 x Aust Divs, all of which would be fully equipped (minus light mortars - they would be replaced by 3 inch mortars), that had plenty of Armour and AT (all of it better than yours) and plenty of AA guns and arty - all operating way closer to supply centers than you are.
4 Jap Divs?, 6?, 8?
Keep in mind Aust can fully equip 8 Divs in 4 Corps and can provide motor transport for them - but can partially equip a lot more.
"And again all this is predicated on a dramatically different 'Midway'. If you also additionally allow a different 'Coral Sea' result, the plausibilities naturally become somewhat more plausable."
Given that none of the Japanese Coral sea commanders had any experience in air ops, nor did they have anyone on their staffs that had air ops experience, Coral sea was never going to go well for Japan.
