Nice to hear it was not a one-time occurance. Yes the japanese AI performed very well on a tactical level, but not on the strategical. They were invading everything at the same time, and I really mean everything: Mauritius, New Guinea, Philippines, Ceylon, Somalia, Oman, Iraq, Persia, Dutch east indies to name some. All of this became half-finished projects because they never completed one objective before engaging the next, like taking only southern part of Phillipines. While it is nice to see them doing unexpected things, they should not drop primary objectives closer to home for doing so. Also I noticed that they put a lot of garrisons in New Guinea (where there are no partisans) but almost none in China. Because of this they had a lot of problems with partisans on the chinese east coast.
But it looks like Nat. China could be an interesting challenge now, will probably try it for my next game.