What does the IJN look like if war delayed six months?

I have not found factors for IJN to postpone the PH operation for six months but, if they have to do, another choice will be to cancel the operation itself immediately and, instead, to send the fleet to the Indian Ocean at the same time. To destroy the logistic lines between UK and the Southwest Pacific will make it possible for IJN to secure oil and time to consider the future step with the US. This is not my imagination but was another choice suggested by a war economy research unit settled in IJA. In July 1941, the unit concluded that there was no chance to win the US but UK. IJN ignored it at once.

Shortround6 said:

Doesn't look good for tanks, or artillery or other army supplies/equipment.
ACF was building over 210 M3 light tanks a month from July 1941 on.
The M3 Medium was being tooled up the fall of 1941 with both different engines and different hull construction (riveted, welded, cast) PH may have speeded thing up a bit but all of the production planning was done and different engines types tested and so on.

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US tank production was a bit more advanced than you seem to believe.

M3 Medium production had begun in June 1941 at Baldwin Loco Works & ALCO followed by the Chrysler run Detroit Tank Arsenal in July, Pullman Standard & Pressed Steel Car in Aug. The DTA alone built 194 M3 Lee in Nov 1941.

The T6 (aka the prototype M4A1 Sherman) was rolled out for presentation on 3 Sept 1941. The first production Sherman was rolled out of the Lima Locomotive Works on last day of Feb 1942.

The Sherman began to supercede the M3 Lee on the production lines from early 1942. The US Govt took over a British funded plant in Nov 1941 and awarded Pressed Steel a Sherman contract for 900 tanks. It completed its first Shermans in March 1942 and its last M3 Grant against the British contract in July 1942.

British orders for tanks in Oct 1940 had provided the funding to kick start US medium tank production.

EwenS said:

US tank production was a bit more advanced than you seem to believe.

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Thank you.
I am trying to be conservative and only count peacetime production. Which is why I didn't count the M4 Sherman.

I have very little interest in trying to argue exactly how fast US production speed up after PH. We all know it did.
But the US far exceeding Japanese production of just about everything even at peace times rates.

Japanese were running out of not only oil but rubber, tin and other materials.

Shinpachi said:

I have not found factors for IJN to postpone the PH operation for six months but, if they have to do, another choice will be to cancel the operation itself immediately and, instead, to send the fleet to the Indian Ocean at the same time.

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Actually, that's what I wanted to say. Without going into details, the wisest game for Japan would be to ignore the USA ( and both Yamamoto and PH) and occupy DEI (with or without a war with the UK). FDR probably would not have succeeded in persuading congress to vote for war over the colonial possessions.
And even if it succeeds... well, the Japanese war plan was a decisive battle, and the Philippines are located very well (as was Port Arthur).
That idea (no PH) has been discussed on several wiff forums.

Shinpachi said:

I have not found factors for IJN to postpone the PH operation for six months but, if they have to do, another choice will be to cancel the operation itself immediately and, instead, to send the fleet to the Indian Ocean at the same time. To destroy the logistic lines between UK and the Southwest Pacific will make it possible for IJN to secure oil and time to consider the future step with the US. This is not my imagination but was another choice suggested by a war economy research unit settled in IJA. In July 1941, the unit concluded that there was no chance to win the US but UK. IJN ignored it at once.

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But geography is against the IJN reaching the IO until it has secured a substantial part of the DEI. All the routes to the IO mean penetrating the Malay Island barrier. Historically they didn't achieve that until mid-Feb 1942 when they bombed Darwin & invaded Timor and Bali and could then support the invasion of eastern Java, by intercepting shipping fleeing south. How successful were the latter operations? (I haven't lookedcat numbers of ships they succeeded in sinking).

And for operations deep into the IO, they need adequate logistics support which has to follow the same route. Historically there wasn't enough to support more than isolated raids either to PH or the IO during Operation C.

The IO is a mighty big area of water to go looking for shipping in.

EwenS said:

But geography is against the IJN reaching the IO until it has secured a substantial part of the DEI. All the routes to the IO mean penetrating the Malay Island barrier. Historically they didn't achieve that until mid-Feb 1942 when they bombed Darwin & invaded Timor and Bali and could then support the invasion of eastern Java, by intercepting shipping fleeing south. How successful were the latter operations? (I haven't lookedcat numbers of ships they succeeded in sinking).

And for operations deep into the IO, they need adequate logistics support which has to follow the same route. Historically there wasn't enough to support more than isolated raids either to PH or the IO during Operation C.

The IO is a mighty big area of water to go looking for shipping in.

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They will be wise enough to go into the Indian Ocearn after the occupation of Malaya, Singapore and DEI pivoting FIC as it happened in fact.