The Battle of Dien Bien Phu was a climactic confrontation of the First Indochina War that took place between 13 March and 7 May 1954. It was fought between the French Union's colonial Far East Expeditionary Corps and Viet Minh communist revolutionaries. The United States was officially not a party to the war, but it was secretly involved by providing financial and material aid, which included CIA contracted American personnel participating in the battle.
The French began an operation to insert, then support, their soldiers at Điện Biên Phủ, deep in the west of Tonkin, up in the hills of northwestern Vietnam. The operation's purpose was to cut off Viet Minh supply lines into the neighboring Kingdom of Laos, 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 and managed to move these bulky weapons through difficult terrain up the rear slopes of the mountains.