The Battle of Dien Bien Phu, fought from March 13 to May 7, 1954, was a decisive Vietnamese military victory that brought an end to French colonial rule in Vietnam. In its wake came the separation of the country into North Vietnam and South Vietnam, creating the political framework for continued conflict and, ultimately, the Vietnam War.

After a millennium of Chinese control over Southeast Asia and Vietnam ended in 969, a series of imperial dynasties ruled for the next 915 years. French traders began trading in Vietnam in the 17th century, eventually joined by French Christian missionaries. To protect them, French military incursions began in 1858. By 1884, Vietnam, Laos and Cambodia had become a French colony known as French Indochina.

After World War II, France sought to reestablish its control over the region. It sent troops to restore colonial rule. They were opposed by the Viet Minh, a Communist-based movement headed by Vietnamese nationalist Ho Chi Minh that sought independence for Vietnam.

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The Viet Minh began fighting against the French in 1946 in what became known as the First Indochina War, first using guerrilla tactics and then more conventional methods of warfare as it received weapons and financial support from the Soviet Union and China.

In November 1953, thousands of French paratroopers dropped into the Dien Bien Phu Valley in the mountainous far northwest region of Vietnam near the Laotian border. They took possession of a small airstrip there and began creating a military stronghold that included a chain of fortified garrisons on a 40-mile perimeter around the airstrip.

The French brought in more than 15,000 troops but this sizeable force was stretched thin defending the large perimeter. And they were badly outnumbered. The Viet Minh had almost 50,000 troops under the command of Gen. Vo Nguyen Giap, an ardent Communist who is considered one of the 20th century’s greatest military strategists.

France had two primary objectives in its occupation of Dien Bien Phu. It sought a base from where it could attack and cripple the supply lines into Laos that supported the growing insurgency in that country. And it wanted to provoke the Viet Minh into an open, massed attack, confident that French forces would prevail in this type of warfare.

The French underestimated Giap’s leadership as well as the Viet Minh army’s weapons and capabilities. The French forces expected to rely on the airstrip to resupply the bastion, wrongly assuming that the Viet Minh had no anti-aircraft weapons.

Giap did nothing to try to stop the initial incursion. For four months, his troops prepared. They spread out through the steep hills until the army literally surrounded the Dien Bien Phu valley. They dug out well-protected artillery positions and somehow manhandled huge artillery pieces up and down the steep slopes and through dense growth to their positions.

On March 13, 1954, under the dark sky of a new moon, the Viet Minh artillery began shelling one of the French perimeter garrisons and the army laid siege to the entire French outpost. The next day, Giap’s artillery disabled the airstrip and his troops attacked and captured another perimeter garrison.

For the next two months, under the cover of artillery fire that the French could not suppress, the Viet Minh forces adopted the type of trench warfare seen in World War I, digging closer and closer to the French lines while working to isolate the remaining French garrisons. The French Air Force, without an operational airstrip, had to drop supplies by parachute while under fire. It lost 62 aircraft during the battle; another 167 were damaged.

On March 30, 1954, Viet Minh troops attacked two more garrisons. Bloody, desperate attacks and counterattacks raged for almost a week as the French fought with fierce resolve but continued to give way. By April 22, Giap’s forces had captured 90 percent of the airstrip, forcing the cessation of the air drops and leaving the French army in dire and deteriorating conditions.

The human toll on both sides was tremendous and Giap had to call for reinforcements from Laos before resuming ground attacks on the shrinking French perimeter on May 1. The end came on May 7, as the last shred of French resistance crumbled, and a triumphant Vietnamese soldier stood atop the conquered French headquarters waving the red and yellow Viet Minh flag in victory.

The 57-day battle was a complete rout for the French army, which lost more than 2,200 soldiers killed in action, and almost 11,000 more who were captured, including more than 5,100 who were wounded. Only about 3,300 of the French prisoners of war made it home. Thousands died in captivity as the French negotiated its exit from Indochina during the 1954 Geneva Conference.

The terms of the July 1954 peace agreement called for a temporary partition dividing north and south Vietnam that was supposed to end with unified national elections in 1956. The elections never happened. Two distinct countries emerged, with Communist North Vietnam supported by the USSR and China and South Vietnam supported by the United States and some of its allies.

The push for Vietnam’s complete independence did not stop, and in South Vietnam, insurgents coalesced as the Viet Cong. With the support of North Vietnam and its army, the Viet Cong engaged in guerilla warfare to challenge the ever-growing U.S. force, leading to the Vietnam War, also known as the Second Indochina War, which stretched from the 1950s to the 1970s.

In 1973, the U.S. withdrew its combat troops. Two years later, on April 30, 1975, South Vietnam fell and Vietnam became a unified and independent Communist country. Its old capital, Saigon, was renamed Ho Chi Minh City.

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Today, Dien Bien Phu is a popular Vietnam historical tourist attraction. It has a modern museum and much of the battlefield is preserved, including several of the fortified French positions, the bunkered French headquarters and the Viet Minh headquarters complex. Regular commercial flights from Hanoi land at the same airstrip, now paved in concrete.

“An Analysis of the French Defeat at Dien Bien Phu,” by Major Harry D. Bloomer, USA, GlobalSecurity.org.

“Dien Bien Phu and the Fall of French Indochina,” Office of the Historian, Foreign Service Institute, United States Department of State.

“Dien Bien Phu: Digging Into History,” (Dien Bien Phu today), by Stephen Grenville, The Interpreter, Lowy Institute.

“Dien Bien Phu,” FactsandDetails.com.

“What the French Lost at Dien Bien Phu,” by Geoffrey Norman, history.net.