The Battle of Điện Biên Phủ was a defeat of the French Union forces by the Viet Minh forces in the First Indochina War. It took place between 13 March and 7 May 1954.
The French began an operation to insert, and support, their soldiers at Điện Biên Phủ, deep in the autonomous Tai Federation in northwest Tonkin. The operation's purpose was to cut off enemy supply lines into the neighboring Kingdom of Laos (a French protectorate) and draw the Viet Minh into a major confrontation in order to cripple them. The French based their forces in an isolated but well-fortified camp that would be resupplied by air, a strategy adopted based on the belief that the Viet Minh had no anti-aircraft capability.
The communist Viet Minh, however, under General Võ Nguyên Giáp, surrounded and besieged the French. 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. They dug tunnels and arranged the guns to target the French positions. The tunnels featured a front terrace, onto which the Viet Minh would pull their cannons from out of the tunnels, fire a few shots, to then pull them back into protective cover.
In March, the Viet Minh began a massive artillery bombardment of the French defenses. The strategic positioning of their artillery made it nearly impervious to French counter-battery fire. Tenacious fighting on the ground ensued, reminiscent of the trench warfare of World War I. At times, the French repulsed Viet Minh assaults on their positions while supplies and reinforcements were delivered by air. As key positions were overrun, the perimeter contracted, and the air resupply on which the French had placed their hopes became impossible as aircraft were shot down and runways were destroyed.
After a two-month siege, the garrison was overrun, with the surviving French forces forced to surrender. Although it did not significantly alter the strategic situation in Indochina, the defeat at Điện Biên Phủ brought a profound psychological shock to France. It led to a gradual withdrawal of French forces from all of Indochina (with the exception of Laos). This was agreed in the 1954 Geneva Accords signed ten weeks after the battle. Accordingly, Vietnam was also temporarily divided at the 17th parallel, with the North assigned to the Democratic Republic of Vietnam under Ho Chi Minh, and the South to the State of Vietnam under Bao Dai and Ngo Dinh Diem.
By 1953, the First Indochina War was not going well for France. A succession of commanders – Philippe Leclerc de Hauteclocque, Jean Étienne Valluy, Roger Blaizot, Marcel Carpentier, Jean de Lattre de Tassigny, and Raoul Salan – had proven incapable of suppressing the insurrection of the Viet Minh, who were fighting for independence. During their 1952–1953 campaign, the Viet Minh had overrun vast swathes of Laos, Vietnam's western neighbor, advancing as far as Luang Prabang and the Plain of Jars. The French were unable to slow the advance of the Viet Minh, who fell back only after outrunning their always-tenuous supply lines. 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, Nà Sản to the west of Hanoi, and the Plain of Jars in northern Laos.
In May 1953, French Premier René Mayer named Henri Navarre as Salan's successor to command French Union forces in Indochina. Mayer had given Navarre a single order—to create military conditions that would lead to an "honorable political solution". According to military scholar Phillip Davidson:
On arrival, Navarre was shocked by what he found. There had been no long-range plan since de Lattre's departure. Everything was conducted on a day-to-day, reactive basis. Combat operations were undertaken only in response to enemy moves or threats. There was no comprehensive plan to develop the organization and build up the equipment of the Expeditionary force. Finally, Navarre, the intellectual, the cold and professional soldier, was shocked by the "school's out" attitude of Salan and his senior commanders and staff officers. They were going home, not as victors or heroes, but then, not as clear losers either. To them the important thing was that they were getting out of Indochina with their reputations frayed, but intact. They spared little thought or concern for the problems of their successors.
Nà Sản and the hedgehog concept
Navarre began searching for a way to address the Viet Minh threat to Laos. Colonel Louis Berteil, commander of Mobile Group 7 and Navarre's main strategist, formulated the hérisson ('hedgehog') concept. The French army would establish a fortified airhead by airlifting soldiers to positions adjacent to key Viet Minh supply lines to Laos. They would cut off Viet Minh soldiers fighting in Laos and force them to withdraw. "It was an attempt to interdict the enemy's rear area, to stop the flow of supplies and reinforcements, to establish a redoubt in the enemy's rear and disrupt his lines".
The hérisson was based on French experiences at the Battle of Nà Sản. 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. There, the French beat back Giáp's forces repeatedly, inflicting very heavy losses on them. The French hoped that by repeating the strategy on a much larger scale, they would be able to lure Giáp into committing the bulk of his forces to a massed assault. This would enable superior French artillery, armor, and air support to decimate the exposed Viet Minh forces. The success at Nà Sản convinced Navarre of the viability of the fortified airhead concept.
However, French staff officers failed to treat seriously several crucial differences between Điện Biên Phủ and Nà Sản: First, at Nà Sản, the French commanded most of the high ground with overwhelming artillery support. At Điện Biên Phủ, however, the Viet Minh controlled much of the high ground around the valley, their artillery far exceeded French expectations, and they outnumbered the French troops four to one. Giáp compared Điện Biên Phủ to a "rice bowl", where his troops occupied the edge and the French the bottom. Second, Giáp made a mistake at Nà Sản by committing his forces to reckless frontal attacks before being fully prepared. 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. He obtained crucial intelligence on French artillery positions from Viet Minh spies posing as camp laborers. Artillery pieces were sited within well-constructed and camouflaged casemates. As a result, when the battle finally began, the Viet Minh knew exactly where the French artillery pieces were, while the French did not even know how many guns Giáp possessed. Third, the aerial resupply lines at Nà Sản were never severed, despite Viet Minh anti-aircraft fire. 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.
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". 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. Navarre selected Điện Biên Phủ for Berteil's "hedgehog" operation. When presented with the plan, every major subordinate officer – Colonel Jean-Louis Nicot (commander of the French Air transport fleet), Cogny, and Generals Jean Gilles and Jean Dechaux (the ground and air commanders for Operation Castor, the initial airborne assault on Điện Biên Phủ) – protested. Cogny pointed out, presciently, that "we are running the risk of a new Nà Sản under worse conditions". Navarre rejected the criticisms of his proposal and concluded a 17 November conference by declaring that the operation would begin three days later, on 20 November 1953.