I really like the idea behind the high-ground system. The downhill advantage adds an interesting tactical layer, although I think the difference between attacking uphill and downhill could be communicated a little more clearly the first time it appears. A small visual cue or short tutorial message could help players understand the mechanic without having to learn it through losing a unit.
I also like the Orders system because having a limited stock makes each use feel like an actual decision rather than something you can spam. It adds another layer of resource management to each march.
Overall, the mechanics have some interesting strategic depth, and I think a little more visual feedback when introducing the less obvious rules would make them much easier to learn while keeping the challenge intact.