I stand corrected. However, they (USSR) could declare war upon Japan and then attack a neutral such as Turkey, right?
No again, sorry:
@rulebook:
Due to its separate treaties with Germany and Japan, the Soviet Union is in a unique position in its relationship with the
Axis powers. As a result, if the Soviet Union is at war with Axis powers on only one map, it is still under the restrictions
of being a neutral power (see “Powers Not at War with One Another,” page 15) on the other map, and Axis powers on
the other map are also still under those restrictions regarding the Soviet Union on both maps. For example, a state of
war with only Japan lifts the neutrality restrictions from the Soviet Union on the Pacific map only, and allows Japanese
units to attack or fly over Soviet-controlled territories on either map. However, the Soviet Union is still restricted on
the Europe map, …