The French began an operation to insert, then support, their soldiers at Điện Biên Phủ, deep in the hills of northwestern Vietnam. The operation's purpose was to cut off Viet Minh supply lines into the neighboring Kingdom of Laos (a French ally), and draw the Viet Minh into a major confrontation in order to cripple them. The plan was to resupply the French position by air - based on the belief that the Viet Minh had no anti-aircraft capability. The Viet Minh, however, under General Võ Nguyên Giáp, surrounded and besieged the French. They brought in vast amounts of heavy artillery (including anti-aircraft guns) and managed to move these bulky weapons through difficult terrain up the rear slopes of the mountains. The Viet Minh then dug tunnels through the mountain and emplaced the artillery pieces overlooking the French encampment.