Battle of Dien Bien Phu
Dien Bien Phu is a valley and small town in North Vietnam, 260 miles northwest of Hanoi and the place of the 1954 decisive battle that soon forced France to relinquish control of colonial Indochina. In military shorthand, Dien Bien Phu has also become a synonym for an extremely unwise decision: the attempt to hold a seemingly strong defensive position, against which the enemy, cooperating with the defender's plans, will then destroy himself against the impregnable fortifications. Unfortunately, the Viet Minh, commanded by Vo Nguyen Giap, did not play the part the French commander, Henri Navarre, had written for them.
That the correct Vietnamese name for the area is not even Dien Bien Phu characterizes the misunderstandings that went into the battle. Properly, the area centers on a village called Muong Thanh by the T'ai tribesmen of the area. 
Previous military use
In 1952, Giap had recognized the French were weak in Laos, and sent three divisions and an independent regiment southwest from his mountainous bases. They pushed the French back, clearing road junctions and capturing small towns including Muong Thon, also known as Dien Bien Phu.
He was able to lay siege to the capital of the capital at Luang Prabang, but, learning caution, decided not to press the attack into the rainy season. In November, French paratroopers recaptured the town, although this was not part of the main fortification. Both sides decided to reinforce for the battle that would begin in March. 
Dien Bien Phu was part of a larger Viet Minh strategy, to force the French to commit their mobile forces to static defense and lose the operational initiative. In parallel with it, they marched divisions into the northwest, attacking local "bandits" and attacking the French column retreating from Lai Chau. They saw the French as losing initiative and mobility, as they concentrated at Dien Bien Phu and in the Red River Delta (i.e., Hanoi-Haiphong area).
Another offensive struck out toward middle Laos, especially the airfield at Seno. Threatening Seno forced the French to commit yet more mobile forces to static defense. The Viet Minh plan was to leave only a small reserve to protect the rear, while attacking the Western highlands. Kontum was taken and the French had to form yet another static defense at Pleiku.
In Upper Laos, Viet Minh troops threatened Luang Prabang, again forcing static defense.
The Dien Bien Phu operation
After Giap had drawn the French strength toward Dien Bien Phu, he used backbreaking human work to bring howitzers and anti-aircraft artillery into the hills surrounding the French base. He used his laborers to dig the weapons into impregnable positions: a cannon could fire and be quickly pulled back into the safety of a cave.
He had had orders from the North Vietnamese Polituro to launch human-wave attacks on January 26, which he concluded would play into the French strength. Instead, possibly endangering his life, he called off the order, and continued fortification and besieging until March 13.
"Mission creep" was among the many French military sins. Originally, Navarre had planned to block Viet Minh access to Laos, and interfere with Giap's supply lines and his drug trade. As the Geneva conference of 1954 approached, however, he felt under pressure to produce a decisive victory. Giap saw the Navarre plan as intending to defend the Red River Delta and leave other forces mobile. 
Seizing the base
On November 23, 1953, the French launched Operation Castor, dropping a paratroop force into Dien Bien Phu, using 65 transport aircraft, supported by fighters and bombers.  Once landed, the paratroopers would build an airfield on which heavier equipment could be landed.
BG Jean Gilles, the Airborne commander, expected some resistance, so he used the best available troops for the first landing:
- 6th BCP (Colonial Parachute Battalion), commanded by MAJ Marcel Bigeard, 651 men
- II/1 RCP (2nd Battalion, 1st Regiment of Parachute Light Infantry), MAJ Jean Bréchignac, 569 men
- 17th Company of Airborne Combat Engineers
- battery of 35th Airborne Artillery Regiment, MAJ Jean Milot
- Headquarters, Airborne Battle Group No. 1 (GAP 1), LTC Fourcade, which would command these units plus a followup battalion
Giap's reinterpretation of orders
When North Vietnamese and American troops faced one another at another remote valley, both sides had Dien Bien Phu in mind at the Battle of Khe Sanh.
- Bernard B., Fall (1967), Hell in a Very Small Place: the Siege of Dien Bien Phu, J. B. Lippincott, HVSP, pp. 23-24
- Mallin, Jay (1973), General Vo Nguyen Giap, North Vietnamese Military Commander, Samhar Press, pp. 12-15
- Vo Nguyen Giap (1962), People's war, People's Army, Praeger, PWPA, pp. 161-162
- Moore, Harold G. (Hal) & Joseph L. Galloway (2008), We are soldiers still: a journey back to the battlefields of Vietnam, Harper Collins, pp. 45-46}}
- Moore & Galloway 2008, p. 129
- Giap, PWPA, p. 163
- Fall, HVSP, pp. 1-4