@kdfsjljklgjfg:
In the Pacific board, the USSR and Japan aren’t at war yet. Japan has taken India. Can Soviet tanks move into Persia in the Europe board and block Japanese movement, since the Soviets are at war on the Europe board?
Yes. But you do realize it doesn’t block japan from attacking persia. There’s no punishment for Japan or Russia when they declare war on each other, and you don’t need to make an attack to declare war. So it doesn’t “block” movement for more than the turn it takes Japan to smash through the Russian line in persia.
The only time the mongolians are affected is when it’s a territory adjacent to mongolia (or korea). So as long as they aren’t skirmishing in manchuria, korea, or the soviet far east, they can beat each other up as much as they want and declare war on the first turn if they want to.
There’s actually no reason that Russia would not declare war on Japan on R1, because it opens their territories up for US landings. If Japan’s going to attack, they’ll attack. The state of war between them is irrelevant prior to Japan’s attacks, so why be at peace? No reason at all.