The embrasure of casemate A8, near Bourg St. Pierre. The armament orginally consisted of a 4,7 cm anti-tank gun that was replaced in the fifties by a 9 cm gun. It covered the main road to the Great Saint Bernard Pass. together with the machine-gun of a casemate on the other side of the road. The casemate A8 consists of a firing room with the gun and a small underground sleeping room for the crew.

The 9 cm gun was originally designed as an anti-tank weapon for the infantry. Therefore the total weight has to be as low as possible. This meant has quite thin barrel which allowed a maximum shell velocity of 600 m/s. Since this wasn't enought for a conventional armour piercing shell the gun fired hollow-charge shells which were fin-stabilised. The gun was introduced in the fifties. At those days it could penetrate almost every existing tank in use. However in the eighties it was taken out of service as it was not powerful enough to destroy the modern MBT.