10 Infantry from Russia. (2 From Kazakh, 2 From Novosibirsk, 2 from Evenki National Okrug, 2 From Yakut SSR, 2 From Soviet Far East and 2 from Buryatia SSR.)
4 of those move to Sinkiang to defend.
6 of those either move to Buryatia for 1 turn then retreat to Yakut SSR or move to Yakut SSR immediately.
You don’t need to send anything else.
Remember, Japan’s going to be up 2 for China, 1 for Buryatia, 1 for SFE, 3 for India. That’s only +7 IPC. 37 IPC vs 40 IPC for America and America doesn’t have to worry about building ground forces to hold their core 38 IPC.
That means Japan is immediately thrust into the position of: Should we build men to take Russia or Submarines to stop America?
Add in a potential dual hit on New Guinea and Borneo with England (44.75% Chance of winning both, 7.56% chance of loosing both) and the naval attacks by England on the Transport in SZ 59 (94.4% success rate) and the attack on the SZ 45 submarine which is really a 50/50 battle and you could put Japan in a very serious hole before they even get a chance to move. Doubly so after America plops down 2 Aircraft Carriers and a Fighter in builds added to the 2 fighters on E. W. USA and the Fighter from Hawaii + Battleship, Transport in LA and Destroyer from Panama.