US intentions in case Japan would move south w/o declaring war?

[what's up?]

It is well known that Japan's leaders thought that declaring war on GB and the Netherlands will inevitable bring the US to war as well, hence PH. I'm wondering if that assumption is true. Is there anything published discussing this matter?

Thanks in advance!

[Carl Schwamberger]

There is literature on this, tho a bit thin. From my shelf:

'Secret Allies in the Pacific' by Worth reviews US, Dutch, & Commonwealth cooperation previous to 7 Dec. It has some info on joint plans.

'The Borrowed Years by Ketchum is a thick volume on Roosevlts PoV, decisions, and policies to 7 Dec 1941. You will have to dig thru 600+ pages but there is some info.

'The Pacfic War1041-1945' by Costello has a few small bits in the prewar chapters.

The short answer is Roosevelt, or the Warhawks in general, intended to ask Congress for a DoW as soon as they felt there were the votes. Exactly when that might be is not clear. A second item is the 'War Warning' message sent to all the Pacific commands in late November. It directed all commanders to consider Japanese forces sighted to be hostile and to attack them. That meant Japanese forces straying into US patrols near the Philippines were liable to be attacked. The War Warning order is the clearest item & leads the most directly shooting between Japanese & US forces.

There were some brief & outline joint plans created between a few Pacific HQ before 7 Dec. Staff officers had secretly been meeting to discuss probable actions. The last of these was when the British Admiral Phillips few to Manilia to meet MacAurthur 5-6 December to discuss the joint plans.

[what's up?]

Thank you for your response!

I finde it quite amazing that there is not much to find on that subject matter.