Russia has 18 inf stationed on the Pacific side of the board spaced out over 3 territories (6 per) to deter/taut the Japanese player. If the Russian player gets complacent and doesn’t consolidate all 18 units into Amur, attacking them might be the best strat. Amur is within range of 4 Inf, 1 mec inf and 1 art from Manchuria plus 1 inf from Korea plus all the airforce from Manchuria, Japan, Okinawa, Kiangsu (not saying to use these planes, cause this force is needed for china attacks), plus whatever you wanted to bring over from Japan on their two transports to combat this Russian force.
By attacking Russia it lets Amur be the buffer zone between the rest of the Russian units and Japan’s valuable Korea/Man, thereby Japan could put troops only in Amur to protect it’s northern flank.
Also by removing this threat early on Japan won’t have to secure it northern boarder and can focus on India, Anzac, US.
Other advantages would be that outside of air units Russia can not get an significant offensive pieces to that theater for several rounds, thereby making the possibility of counterattack less likely to succeed.
Attacking Russia also puts some attention on Japan and their Eastern boarder which may distract them slightly from the eventual German attack.
On the flip side of this if Japan doesn’t attack Russia, then they have 18 inf sitting on their nothern boarder waiting for the opportunity to strike, which strike will surely come at somepoint in the game. Attacking Russia does not bring any other nation into war, so Japan can do this without reprisal.
What do others think?