When did many alpine countries develop heavy protection to prevent new invasion?
After the fall of Napoléon, many alpine countries developed heavy protections to prevent any new invasion. Thus, Savoy built a series of fortifications in the Maurienne valley in order to protect the major alpine passes, such as the col du Mont-Cenis that was even crossed by, Charlemagne and his father to defeat the Lombarts. The later indeed became very popular after the construction of a paved road ordered by Napoléon Bonaparte. The Barrière de l'Esseillon is a serie of forts with heavy batteries, built on a cliff with a perfect view on the valley, a gorge on one side and steep mountains on the other side.