Mountainous border in the 18th century? For reasons that are probably pretty obvious, my first thought is Swedish-Norwegian wars of Charles XII (http://en.wikipedia.org/wiki/Charles_XII_of_Sweden). He was killed in Norway, and carried across the border. There's a famous painting. And there are mountans galore, not to mention a border. Snowstorms also figure as well as massive death of innocent soldiers drafted from exotic places. Like Finland. I allways wondered what the locals in the rural mountainous border-regions thought about the war. I mean, the borders are porous as hell even today, and goats don't care if they eat Swedish or Norwegian grass. Goats are also not famous for timetravel.