From: Hex X37, Y15
As I am just conducting a mountain war in the Capathians, I have started thinking about mountains and winter. In WITE, snow and blizzard have the effect of more or less negating rivers, but there is no effect of making mountain warfare more difficult in winter. There is no problem moving a mechanized unit one hex in mountains, even during blizzard, while one would realistically wonder if it was even possible to move large mechanized formations through such terrain even in high summer. Sure, supply is very awkward, but it is entirely possible to infiltrate a tank army through several hexes of mountain. And I have yet to see a unit surrender because of mountain supply restrictions.
I think movement and attacks into mountain hexes in snow or blizzard should be severely restricted, perhaps only mountain units should be able to move into mountains during winter weather. And as for mechanized units I think they should not be able to enter mountains at all except along railroads.
There are plenty of historical examples of fighting in the Carpathians during WW1, when most operations simply ground to a halt in the winter in the mountains, with some notable logistic and freezing disasters where one side or other tried to advance.