While playing around with the Terrain Overlay, click on a stack then tap number 7, I was shocked to see that range in mountains was not the normal 99 it is in all other areas, but rather a tiny 4.
I gather that this means, long distant fire is almost nil in the mountains, and that any medium and heavy artillery is next to useless.
Is this the case?
By the way, cavalry also appears to attack poorly in mountains.