The operation began on 20 November, 1953, when three parachute battalions dropped into the Dien Bien Phu basin, which they seized against light opposition. The French quickly built an airstrip and began flying in troops and materiel, including six light tanks transported in Dieces and assembled on the soot. Enaineers constructed a system of defensive strongholds, which Castries named for his mistresses. A stream of VIPs and experts, including senior U.S. military officers, inspected the position and pronounced it sound.
For a time all seemed well, but Navarre had badly underestimated the Vietminh. Within weeks, French forces attempting to move out of the valley met ambushes which became progressively more intense. By February they were confined to the basin. In the meantime the Vietminh had routed the Tai partisans, and the demoralized survivors who straggled in from the north were of little value. Then, on 13 March, the most basic flaw in Navarre's plan became evident when Vietminh artillery opened up from the surrounding hills, immediately closing the airfield. Dien Bien Phu was isolated except for resupply by airdrop. The French gunners were unable to locate the camouflaged communist guns and the artillery commander committed suicide. The outlying positions of Gabrielle, Beatrice and Anne-Marie were quickly overrun and Vietminh sappers began driving trenches toward the central position in a reversion to eighteenth century siege warfare. Supply shortages loomed as communist anti-aircraft guns - another surprise-forced the resupply drops to higher altitudes, littering the valley floor with parachutes and gratuitously supplying the Vietminh.
Having prepared poorly, the French fought well. Castries, psychologically unfit for grinding siege operations, suffered a breakdown, relinquishing defacto command to a cabal of junior paratroop officers. The morale of the Algerian and Moroccan units cracked at the end, but the paratroops, Foreign Legionnaires, tank crews and gunners fought on with skill and tenacity. There was never a shortage of volunteers to parachute into the doomed fortress, including hundreds of Vietnamese, and the one French surprise for the Vietminh was their ability to mount effective counterattacks. As late as 10 April, the French recaptured a key stronghold at the northeast corner of Elaine and there is evidence that the Vietminh suffered a serious crisis of morale. While the issue was not as preordained as is generally supposed, French miscalculation had put the garrison in a position whereby only a miracle could save it ... and, indeed, a "miracle" was proposed in the form of saturation bombing of the Vietminh positions by U.S. air power, an idea seriously considered in President Eisenhower's inner circle. Additional American aid was offered and aircraft deliveries increased sharply in March and April. But it was too little and too late.
As April slipped away, the Vietminh grip on Dien Bien Phu tightened inexorably. During the night of 6-7 May, 1954, a huge mine pulverized the remains of stronghold Elaine and there was nothing left with which to meet the communist assault. Castries surrendered, and dawn saw Vietminh assault troops waving flags atop his command bunker. Some 7,000 prisoners were marched off to camps in the Bac Viet and northern Annam; nearly half of them were to die en route. France was finished in Vietnam. President Mendes-France entered into negotiations with the Vietminh in Geneva and on July, 1954, at 0343, Geneva time, he signed the accord that marked the formal end of the French phase of the Vietnam War.
In a sense it was a curious accord. Ho did not get all he wanted, nor even all he could have reasonably expected. The French military position was weaker than even the numbers implied, for the losses at Dien Bien Phu included the creme de la creme of the French forces. Vietminh infiltration of the Red River Delta had reached alarming proportions and, as Dien Bien Phu surrendered the main French mobile force in the Central Highlands was being cut to pieces near Pleiku. Yielding to pressure from Soviet Foreign Minister Molotov and his Chinese counter part Choulai, conscious of Soviet and Chinese strategic vulnerabilities and anxious to placate the western democracies, Ho had to be content with the northern half of his country. It was an unstable situation which could not endured.Page 11 (America in Vietnam)