The Battle of Điện Biên Phủ (French: Bataille de Diên Biên Phu; Vietnamese: Chiến dịch Điện Biên Phủ) was the climactic confrontation of the First Indochina War between the French Union's French Far East Expeditionary Corps and Viet Minh communist-nationalist revolutionaries. The battle occurred between March and May 1954 and culminated in a comprehensive French defeat that influenced negotiations over the future of Indochina at Geneva. Military historian Martin Windrow wrote that Điện Biên Phủ was "the first time that a non-European colonial independence movement had evolved through all the stages from guerrilla bands to a conventionally organized and equipped army able to defeat a modern Western occupier in pitched battle."
As a result of blunders in French decision-making, the French began an operation to support the soldiers at Điện Biên Phủ, deep in the hills of northwestern Vietnam. Its purpose was to cut off Viet Minh supply lines into the neighboring Kingdom of Laos, a French ally, and tactically draw the Viet Minh into a major confrontation that would cripple them. The Viet Minh, however, under General Võ Nguyên Giáp, surrounded and besieged the French, who were unaware of the Viet Minh's possession of heavy artillery (including anti-aircraft guns) and their ability to move these weapons through difficult terrain to the mountain crests overlooking the French encampment. The Viet Minh occupied the highlands around Điện Biên Phủ and bombarded French positions. Tenacious fighting on the ground ensued, reminiscent of the trench warfare of World War I. The French repeatedly repulsed Viet Minh assaults on their positions. Supplies and reinforcements were delivered by air, though as the French positions were overrun and the anti-aircraft fire took its toll, fewer and fewer of those supplies reached them. The garrison was overrun after a two-month siege and most French forces surrendered. A few escaped to Laos. The French government resigned and the new Prime Minister, the left of centre Pierre Mendès France, supported French withdrawal from Indochina.
The war ended shortly after the battle with the 1954 Geneva Accords, under which France agreed to withdraw from its former Indochinese colonies. For the north, the French recognised the authority of Ho Chi Minh; for the south, elections would be held to determine its future. Those elections never took place - the Americans canceled them. The accords partitioned Vietnam in two; fighting later broke out between opposing Vietnamese factions in 1959, resulting in the Vietnam (Second Indochina) War.