In 120 days, they don't have 120 days. Hawaii was so far from Japanese supply lines they had to strap barrels of oil on to the sides of their ships. Here is an entire thread on why this is impossible.
https://www.alternatehistory.com/fo...pearl-harbor-as-an-invasion-of-hawaii.424093/
The old Tully and Parshall argument. Note the time? After a presumed victory at Midway. Note the conditions? A half dozen fast fleet oilers have been sunk (Dutch efforts.) The Indonesian oil fields have been sabotaged. The SRA campaign has burned through 800,000 barrels of Japanese heavy fuel and 120,000 barrels of av-gas. The IJA reserve is scattered and committed in a 3 front war in the SRA and yes,
under those conditions with a aroused US fleet and air garrison in Hawaii, invasion of Oahu is impossible.
The April numbers (Coral Sea result.) make it ridiculous.
But I am not talking April or May 1942 when you have an alert defender, the code breakers are active, the Japanese have burned half their oil and scattered their lift to the winds. What I discuss is
September 1941.
Now on January 24 1941, Roosevelt's war honchos, Frank Knox and Henry Stimson, got together and talked HAWAIIAN turkey. The two of them cooked up a letter of instruction (LOI) to be forwarded to the Army and Navy commands IN THAT PLACE. May I quote that letter?
"The dangers [of an attack upon the fleet] envisaged in their order of importance and probability are considered to be: (1) Air bombing attack (2) Air torpedo plane attack, (3) Sabotage, (4) Submarine attack, (5) Mining, (6) Bombardment by gunfire."
Attack Upon Pearl Harbor by Japanese Armed Forces – 77th Congress, Senate Document No. 159.
Was that letter of instruction followed?
Aircraft warning system? Nope.
Offshore air patrol by Army or Navy aircraft? Nope.
AAA deployed and fighter interception plan implemented? Are you kidding? Caught on the ground, the planes destroyed. The AAA battery ammunition ashore and afloat was locked up; the AAA crews were not trained or prepared or by their guns collocated. It's a miracle PACFLT put up the flak she did. The IJN may have been impressed and appalled at the AAA of 7 December, but compared to what a prepared USN could do, it was nothing.
Any kind of system of dispersal and alert 5? Again are you kidding?
How long did it take the national guard division to man unprepared coast defenses that 7 December? 14 hours. With what? Mostly rifles and machine guns. There was coast defense artillery. But it was sited by Spanish American War/WW I logic.
Where do we land? IJA?
Haleiwa beach.
Note the gap?
Can we do it IJA?
Barely if everything goes right. The question is how many Daihatsus will we have left after the first wave claws ashore. Follow on echelons will have to be there immediately. No less than 7 divisions in 140 transports. Ship to shore requires at least 800 Daihatsus. (140 tonne LCIs). Do the Japanese have that?
Unfortunately as the SRA campaign demonstrates. Yes, they do.
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The US PACFLT is still manned at 75% in September 1941 as LANTFLT siphons off the cream of the personnel. Training is still peacetime tempo. Air garrison is fairly strong with 85 Navy/Marine planes of all types and 140 AAC aircraft present. There is the one understrength national guard infantry division (~80%) still trying to bulk up and equip to meet a wartime TOE using obsolete equipment. PACFLT has torpedo, shell and bomb defects it knows nothing about. It will take a half year of war to show them that their pre-war stocks are defective. PACFLT is tanker short almost a dozen oilers as here fleet train has been stripped to support LANTFLT and the neutrality patrol.
The air defense has no radar, aside from the stuff mounted aboard the fleet, no good intercept coordination center ashore, no fleet command center ashore, a staff riddled with imbeciles (Pye and Ghormley for example.) and an admiral who is still stuck in 1935. (Kimmel). As for Short, he is trying and he thinks he knows what he does, but he is sabotage happy and has not pair attention to the Knox/Stinson LOI which is filed away forgotten in Navy and Army headquarters file rooms.
Note this. If the Japanese can take on Singapore and carry it off, a very high risk operation, with the SRA campaign in full swing and add Burma to it, what the hello makes Oahu so ridiculous to contemplate for these madmen who planned the SRA campaign?
I gave them 35% odds of pulling it off
if they commit everything they have. That's actually better odds than they should have had at Lingayen Gulf or Singapore.
Haven't you turned Hawaii into a massive version of Wake and Rabaul combined?
To "stopper" the American fleet you have to defend the base and to defend the base that leaves you devoid of resources to actually acquire the raw materials you need. So the Americans have six months or so to work out how they run a war without Pearl - it probably involves Subic and Singapore, both of which are likely to still be in allied hands given the concentration of Hawaii. Is it an efficient way to run the Allied war - no. Is it more efficient that the Japanese plan of trying to build a fortress Hawaii - yes.
They took and held Rabaul and Wake to the end of the war, remember?
As for Subic, and Singapore? Follow up through Thailand and Indochina/Burma is overland and arduous, but doable without the Indochina convoys. Or they could pull a couple of divisions from around Shanghai and hustle them south. Philippine Islands s is cut off, so there is no resupply of that garrison. it can be taken in a follow up operation.
Now mind you, PACFLT has to be Nagumo clobbered exactly as in the RTL and he will have to stick around to cover the Kondo invasion convoy. That is where it gets dicey, because that is a two week long fight between what's left of PACFLT not at Pearl rushing home, the Americans ashore, and they are more or less wide open to the RN and Dutch until the Oahu operation is finished. Chancy.
And as for balls to the wall? If you are going all in. Go all in.