An elaborate technique of tunnels dug from the mountainsides enabled the Viet Minh to safeguard its artillery pieces by regularly shifting them to circumvent discovery. Many hundred kilometers of trenches permitted the attackers to move progressively closer on the French encampment. \ Pinney et al. (2008) concluded that there are https://www.skypixel.com/users/djiuser-lw0heshxxvvr