‘And this,’ our guide said, ‘is where Colonel Piroth committed suicide.’ We were standing by a fenced-off scrap of wasteland on the edge of a busy market. The only evidence that anything of significance happened there is a white cement block carved with an image of two artillery pieces and an almost illegible inscription in Vietnamese. The entrance to Piroth’s bunker, if it still exists, is overgrown and filled with rubble.

Piroth was the deputy commander of French forces at Dien Bien Phu, a one-armed war hero and gunnery expert who had boasted that ‘no Viet Minh cannon will be able to fire three rounds before being destroyed by my artillery.’ In fact the Viet Minh made short work of the French artillery. ‘I have been dishonoured,’ Piroth said. Soon afterwards, using his teeth, he pulled the safety pin out of a grenade and blew himself to pieces.

Dien Bien Phu was one of the decisive battles of the post-1945 era. Not since the British were turfed out of Afghanistan in the 19th century had an indigenous army inflicted so resounding a defeat on a colonial power. The battlefield was a remote valley in north-west Vietnam, eleven miles by three, encircled by mountains, the best part of two days’ journey from Hanoi along precipitous roads winding through jagged limestone hills. Today it is a bustling town, but in the 1950s the valley was inhabited mainly by people of the T’ai minority who grew rice and smuggled opium.

The French strategy seems to have been to block the route into neighbouring Laos, where an uprising against colonial rule was also underway, and to tempt the Viet Minh into a set-piece battle which the French, with their tanks, artillery and aircraft, were confident of winning. The construction of an airstrip meant they were not dependent on roads and well supplied with heavy weapons. They were taken completely by surprise when, on 13 March 1954, the Viet Minh artillery, much of it recycled US weaponry captured by the Chinese in Korea, opened up on them from the surrounding hills. Before long the air strip was out of action and the French troops were trapped.

The Australian journalist Wilfred Burchett was with Ho Chi Minh ‘at his jungle headquarters’ when the battle began:

‘This is Dien Bien Phu,’ said President Ho as he tipped his sun helmet upside down on the bamboo table. ‘Here are mountains,’ and his slim, strong fingers ran around the outer rim of the helmet, ‘and that’s where we are.’ Then his hand plunged down into the bottom of the helmet: ‘Down there is the valley of Dien Bien Phu – that’s where the French are. The best troops they have in Indo-China. They will never get out.’

Burchett also described the extraordinary logistical feat that enabled the Viet Minh to encircle the valley:

The countryside, so quiet and passive – especially as seen from the air – in daytime, boiled with activity at night. From trucks to oxcarts, bicycles and human backs, every imaginable form of transport hauled supplies through the jungle and up and down the steep mountains ... Before dawn and the inevitable reconnaissance planes, shrubs and trees were planted on those supply lines, to be removed as the convoys started moving again at dusk.

A short walk from the derelict place where Colonel Piroth met his end, across a battered bridge, is the bunker of the French commander, Colonel (later General) Christian Marie Ferdinand de La Croix de Castries, described by the American journalist Stanley Karnow as a ‘lean aristocrat with a Roman profile whose ancestors had soldiered since the crusades. Irresistible to women and riddled with gambling debts, he had been a champion horseman, dare devil pilot and courageous commando.’ The three French artillery bases – Gabrielle, Beatrice and Isabelle – were allegedly named after his mistresses. His heavily sand-bagged bunker is well preserved and can be visited for 60,000 dong (£2). It is rather better appointed than Colonel Piroth’s.

Close to what is now the town centre is a 32-metre hill criss-crossed with trenches and bunkers which the Viet Minh did not succeed in capturing until the final day of the battle, 7 May. Towards the end they brought in coal miners from Hong Gai who, unseen by the defenders, dug a long tunnel under the hill and packed it with a thousand pounds of explosives. The crater has been preserved for posterity.

As Vietnam grows in prosperity Dien Bien Phu is an increasingly popular attraction for domestic tourists. There is a large museum, the highlight of which is a huge circular mural, said to have been the work of two hundred artists, depicting every detail of the battle. There are four flights a day from Hanoi and innumerable air-conditioned tour buses winding their way overland.

Up in the hills, the headquarters of the Vietnamese commander, Vo Nguyen Giap, has also been added to the tourist itinerary. It consists of a handful of thatched bamboo huts and a series of rooms dug into the side of a hill, spread out along a forest track. Next to the car park a temple has been erected in Giap’s honour. The centre piece is a large golden bust on an altar piled high with offerings. You wonder what he would have made of it.

The battle at Dien Bien Phu lasted 55 days. On 8 May 1954 the French government announced that France would withdraw from Vietnam. The casualties on both sides were horrendous. About eight thousand Viet Minh were killed and twelve thousand wounded. French casualties, many of whom were recruited from their North African colonies, numbered 2200 dead and 5600 wounded. Many more died on the long march into captivity.

A great power conference underway at Geneva, having dealt with Korea, was about to turn its attention to Vietnam. Given that the French had announced their intention to withdraw, it ought to have been easily resolved. All that was required was to organise an orderly departure followed by internationally supervised elections.

The Americans, however, were having none of it. Already they were bankrolling much of the cost of the French war and for some time the secretary of state, John Foster Dulles, had been trying to persuade President Eisenhower to use B-29 bombers to help relieve the French. Eisenhower refused, saying he would not contemplate direct intervention without the support of both Congress and America’s allies, notably Britain. Dulles flew to London but for once Eden and Churchill wouldn’t co-operate. According to the French foreign minister, Georges Bidault, Dulles had taken him aside on the eve of the Geneva conference and offered him atom bombs.

The Americans went to Geneva determined to undermine any settlement. Dulles refused even to shake hands with the Chinese prime minister, Zhou Enlai. The Chinese and the Russians were anxious to prevent another war in Asia and leaned heavily on the Vietnamese to make concessions. In the end it was agreed that Vietnam would be temporarily divided at the 17th parallel, pending elections to be held within two years. The Americans refused to sign. Eisenhower wrote in his memoirs:

I have never talked or corresponded with a person knowledgeable in Indo-Chinese affairs who did not agree that, had elections been held at the time of the fighting, possibly 80 per cent of the population would have voted for Ho Chi Minh.

He was being disingenuous. There was little or no fighting in the two years following Geneva.

Although they had pledged not to undermine the Geneva Agreement the Americans immediately set about doing so. In the South they created and armed an artificial regime under a stubborn and ruthless mandarin, Ngo Dinh Diem. The CIA set up the Saigon Military Mission under Colonel Edward Lansdale, a specialist in psychological warfare and dirty tricks. In the North, which was not yet under fully under Viet Minh control, the CIA sent in agents under Major Lucien Conein with instructions to sabotage the transport network. They contaminated the fuel supply for Hanoi’s buses and concealed explosives in the coal supplies destined for the railway. It would be another 17 years before any of this became public with the release of the Pentagon Papers. Rumours were also spread among the superstitious northern Catholics that ‘the Virgin had gone south’ and a massive evacuation was organised.

The elections decreed by the Geneva Agreement never took place. The southern arm of the Viet Minh, who had regrouped to the North following Geneva, grew increasingly impatient and, despite being discouraged by the Hanoi government, who had enough problems of their own, began to infiltrate the South. By 1961 a new war was underway, in which at least a million Vietnamese were destined to die and much of the country reduced to ruins. A war that might have ended at Dien Bien Phu lasted another twenty years.

John Foster Dulles never lived to see the mayhem he caused. He died in 1959. Ho Chi Minh did not live to see his country reunited, dying in 1969. General de Castries lived until 1991. As for Vo Nguyen Giap, the school teacher turned general, he outlived them all, dying in 2013 at the age of 102.