I've seen this with France vs Japan the UK vs Japan and now Netherlands vs Japan.
Japan AI will send large fleets to Northern Europe, the Indian Ocean and West Africa and they have ZERO bases there. I've seen them occasionally in the Caribbean and Mediterranean.
Japan has NO business sending their fleets so far away where they can't support their holdings in SEAsia and Northeast Asia. The AI has got to be updated so it stops doing this. Japan's fleet is already small and dividing it up reduces their ability to effectively fight and their ships end up in the yard from maintenance issues in sea zones with no bases and it's disheartening to see the AI act so stupidly splitting up their fleet and sending them all over the world. I expect more from the AI in this regard.
Unusually, I have not seen Italy behave similarly. They usually keep to the Mediterranean, West Africa, Indian Ocean and sometimes Northern Europe, but mostly the AI stays in the Mediterranean Sea.
Just wondering if this is WAI, or is a bug. At the outset of a war, Japan will spread its fleet all over the world leaving just a few BB's and BC's to guard NEA and SEA. I dont like them doing that. IMO., it's not realistic. They have no bases from which to operate their fleet in foreign ports during war. I think they need to stay put where they have base capacity and defend their interests. This also prevent any sort of fleet battle because their fleets are dispersed.
Is there some justification for why they split up their fleet and try to blockade you half a world away?