The operation's purpose was to cut off enemy 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.

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.

With huge support by the U.S., the south became the State of Vietnam, nominally under Emperor Bảo Đại, preventing Ho Chi Minh from gaining control of the entire country.

In 1953, the French had begun to strengthen their defenses in the Hanoi delta region to prepare for a series of offensives against Viet Minh staging areas in northwest Vietnam.

They set up fortified towns and outposts in the area, including Lai Châu near the Chinese border to the north,[18] Nà Sản to the west of Hanoi,[19] and the Plain of Jars in northern Laos.

In late November and early December 1952, Giáp had attacked the French outpost at Nà Sản, which was essentially an "air-land base", a fortified camp supplied only by air.

[31] He learned his lesson: at Điện Biên Phủ, Giáp spent months meticulously stockpiling ammunition and emplacing heavy artillery and anti-aircraft guns before making his move.

At Điện Biên Phủ, Giáp made it a priority for his gunners to focus on the French runways and aircraft, crippling supply runs and making it impossible for fresh soldiers to be sent in.

[33] In June 1953, Major General René Cogny, the French commander in the Tonkin Delta, proposed Điện Biên Phủ, which had an old airstrip built by the Japanese during World War II, as a "mooring point".

[34] In another misunderstanding, Cogny envisioned a lightly defended point from which to launch raids; Navarre, however, believed that he intended to build a heavily fortified base capable of withstanding a siege.

[45] Starting in December, the French, under the command of Colonel Christian de Castries, began transforming their anchoring point into a fortress by setting up seven satellite positions.

[48] French military forces had committed 10,800 troops, together with yet more reinforcements, totalling nearly 16,000 men, to the defense of a monsoon-affected valley surrounded by heavily-wooded hills and high ground that had not been secured.

Artillery as well as ten US M24 Chaffee light tanks (each broken down into 180 individual parts, flown into the base, and then re-assembled) and numerous aircraft (attack and supply types) were committed to the garrison.

[54][55][56][page needed] The Viet Minh assault began in earnest on 13 March 1954 with an attack on the northeastern outpost, Béatrice, which was held by the 3rd Battalion, 13th Foreign Legion Demi-Brigade.

In the north, most of Beatrice-1 was swiftly conquered by the 141st Regiment's 428th Battalion, but the defenders held out in corner of the position for a time because the attackers thought they had captured the entire strong point when they encountered an internal barbed wire barrier in the dark.

Indirect artillery, generally held as being far superior to direct fire, requires experienced, well-trained crews and good communications, which the Viet Minh lacked.

"[61] Two days later, the French artillery commander, Colonel Charles Piroth, distraught at his inability to silence the well-camouflaged Viet Minh batteries, went into his dugout and committed suicide with a grenade.

The Viet Minh further encircled the French central area (formed by the strong points Huguette, Dominique, Claudine, and Eliane), effectively cutting off Isabelle and its 1,809 personnel to the south.

On 27 March, the Hanoi air transport commander, Nicot, ordered that all supply deliveries be made from 2,000 m (6,600 ft) or higher; losses were expected to remain heavy.

[73] The next phase of the battle saw more massed Viet Minh assaults against French positions in central Điện Biên Phủ – particularly at Eliane and Dominique, the two remaining outposts east of the Nam Yum River.

[75] At this point, the French 4th Colonial Artillery Regiment entered the fight, setting its 105 mm howitzers to zero elevation and firing directly on the Viet Minh attackers, blasting huge holes in their ranks.

Repeated attempts to reinforce the French garrison by parachute drops were made, but had to be carried out by lone planes at irregular times to avoid excessive casualties from Viet Minh anti-aircraft fire.

[82] Worse still, the Viet Minh lacked advanced medical treatment and care, leading a US general commenting on the war to observe that "Nothing strikes at combat-morale like the knowledge that if wounded, the soldier will go uncared for".

[99] Militarily there was no point in France fighting on, as the Viet Minh could repeat the strategy and tactics of the Dien Bien Phu campaign elsewhere, to which the French had no effective response.

Code named opération Églantine, GM.100, however were hit in a series of deadly ambushes at the Battle of Mang Yang Pass, suffering heavy losses in men and vehicles by 29 June and the remnants struggled back to Pleiku.

42' (GM.42) in an armoured convoy was sent to relieve the units, but were ambushed at the Battle of Chu Dreh Pass on July 17, just four days before the armistice suffering further heavy losses and the almost complete destruction of Bataillon de Corée.

The event itself was in fact, both in terms of public opinion and of the military conduct of the war and operations, merely the end result of a long process of degradation of a faraway enterprise which, not having the assent of the nation, could not receive from the authorities the energetic impulse, and the size and continuity of efforts required for success.

The Algerian National Liberation Front viewed it as an epoch-changing moment, with Ferhat Abbas, post-colonial Algeria's first president, declaring:Dien Bien Phu was more than just a military victory.

[120] According to the Mutual Defense Assistance Act, the United States provided the French with material aid during the battle – aircraft (supplied by the USS Saipan), weapons, mechanics, 24 CIA/CAT pilots, and U.S. Air Force maintenance crews.

[131] Earlier, in order to succeed the pre-Điện Biên Phủ Operation Castor of November 1953, General Chester McCarty made available twelve additional C-119 Flying Boxcars flown by French crews.