Japan has 5 Transports. Why would they need more? They’d be better off buying 3 Infantry and 2 Artillery, so that they have more stuff to land next turn. Also, Japan already has enough ground units to take Eurasia if it is using its air support properly. They should attack East Asia with 12 Infantry and an Artillery, and hitting Philipines, Borneo, and East Indies with 2 more Infantry apiece, of which the Borneo and East Indies drops can be transported to India or Australia the following turn, while the surviving Infantry in the Philipines can take New Guinea.
Why do they need more? You answered your own question. They need the additional TPs because the ones they start with will be in the south pacific, not in the sea of Japan shuttling your unit purchases to asia. 5 TPs just isn’t enough to do everything quickly enough. In fact, I’ve bought an 8th TP in many games, which allows you to set up a 4x4 chain to Alaska once the south pacific TPs return home.
At the end of J1, you should have 3 inf on Japan plus either the starting artillery unit. So you drop 2 more TPs and an inf, now you can move all 5 units on Japan plus the Iwo Jima inf with the help of only 1 starting TP (which is probably in sz61). The other 4 TPs will be in use elsewhere. With an all tech buy on J1, these extra units don’t get to asia next turn, since you won’t have the capacity to move them on J2.
Buying 3 inf, 2 art on J1 would be pretty pointless, since they’d just be sitting idle on Japan doing nothing because you can’t get them into Asia for the reasons already mentioned.
