During World War II, the Soviet Union and Japan had a five year mutual non-aggression pact that was kept until the very end. Could a similar thing happen in Allies and Axis?
In some versions of the game, this policy is "enforced" by the fact that it costs 5 or even 10 IPCs for one side to attack the other's territories. Would you play such a game variation?
In other games, there are understandings between the two countries, derived during table talk. This may include not reinforcing territories that the other is likely to attack. For instance, Russia can reinforce British forces that have captured Norway, but not British forces in India.
Would you try to conclude such an agreement with the other party if you were playing Japan? Russia?