A storm swept the world in 1968. It started in Vietnam, then blew across Asia, crossing the sea and the mountains to Europe and beyond. A brutal war waged by the US against a poor south-east Asian country was seen every night on television. The cumulative impact of watching the bombs drop, villages on fire and a country being doused with napalm and Agent Orange triggered a wave of global revolts not seen on such a scale before or since.

If the Vietnamese were defeating the world's most powerful state, surely we, too, could defeat our own rulers: that was the dominant mood among the more radical of the 60s generation.

In February 1968, the Vietnamese communists launched their famous Tet offensive, attacking US troops in every major South Vietnamese city. The grand finale was the sight of Vietnamese guerrillas occupying the US embassy in Saigon (Ho Chi Minh City) and raising their flag from its roof. It was undoubtedly a suicide mission, but incredibly courageous. The impact was immediate. For the first time a majority of US citizens realised that the war was unwinnable. The poorer among them brought Vietnam home that same summer in a revolt against poverty and discrimination as black ghettoes exploded in every major US city, with returned black GIs playing a prominent part.

The single spark set the world alight. In March 1968, students at Nanterre University in France came out on to the streets and the 22 March Movement was born, with two Daniels (Cohn-Bendit and Bensaid, Nanterre students then, and both still involved in green or leftist politics) challenging the French lion: Charles de Gaulle, the aloof, monarchical president of the Fifth Republic who, in a puerile outburst, would later describe as chie-en-lit - "shit in the bed" - the events in France that came close to toppling him. The students began by demanding university reforms and moved on to revolution.

That same month in London, a demonstration against the Vietnam war marched to the US embassy in Grosvenor Square. It turned violent. Like the Vietnamese, we wanted to occupy the embassy, but mounted police were deployed to protect the citadel. Clashes occurred and the US senator Eugene McCarthy watching the images demanded an end to a war that had led, among other things, to "our embassy in Europe's friendliest capital" being constantly besieged. Compared with the ferment elsewhere, Britain was a sideshow ("...in sleepy London Town there's just no place for a street fighting man," Mick Jagger sang later that year): university occupations and riots in Grosvenor Square did not pose any real threat to the Labour government, which backed the US but refused to send troops to Vietnam.

In France, the existentialist philosopher Jean-Paul Sartre was at the peak of his influence. Contrary to Stalinist apologists, he argued that there was no reason to prepare for happiness tomorrow at the price of injustice, oppression or misery today. What was required was improvement now.

By May, the Nanterre students' uprising had spread to Paris and to the trade unions. We were preparing the first issue of The Black Dwarf as the French capital erupted on May 10. Jean-Jacques Lebel, our teargassed Paris correspondent, was ringing in reports every few hours. He told us: "A well-known French football commentator is sent to the Latin Quarter to cover the night's events and reported, 'Now the CRS [riot police] are charging, they're storming the barricade - oh my God! There's a battle raging. The students are counter-attacking, you can hear the noise - the CRS are retreating. Now they're regrouping, getting ready to charge again. The inhabitants are throwing things from their windows at the CRS - oh! The police are retaliating, shooting grenades into the windows of apartments...' The producer interrupts: 'This can't be true, the CRS don't do things like that!'

" 'I'm telling you what I'm seeing...' His voice goes dead. They have cut him off."

The police failed to take back the Latin Quarter, now renamed the Heroic Vietnam Quarter. Three days later a million people occupied the streets of Paris, demanding an end to the rottenness of the state and plastering the walls with slogans: "Defend The Collective Imagination", "Beneath The Cobble- stones The Beach", "Commodities Are The Opium Of The People, Revolution Is The Ecstasy Of History".

Eric Hobsbawm wrote in The Black Dwarf: "What France proves is when someone demonstrates that people are not powerless, they may begin to act again."

I had been planning to head for Paris - it was something we had been discussing at the paper - but then I received a late-night phone call. A posh voice said, "You don't know who I am, but do not leave the country till your five years here are up. They won't let you back." In those days, citizenship for Commonwealth citizens was automatic after five years. I would not complete my five years until October 1968. Already Labour cabinet ministers had been discussing in public whether or not I could be deported. Friendly lawyers confirmed I should not leave the country. Clive Goodwin, the publisher of our mag, vetoed the trip and went off himself.

I went a year later to help Alain Krivine, one of the leaders of the May 1968 revolt, in his presidential campaign, standing for the Ligue Communiste Révolutionnaire. As we touched down at Orly airport, returning from a rally in Toulouse, the French police surrounded the plane. "Hope it's you, not me," muttered Krivine. It was. I was served an order banning me from France which stayed in force until François Mitterand's election many years later.

The revolution did not happen, but France was shaken by the events. De Gaulle, with a sense of history, considered a coup d'état: in early June, he flew from a military base to Baden-Baden, where French troops were stationed, to ask whether they would support him if Paris fell to the revolutionaries. They agreed but demanded rehabilitation for the ultra-right generals whom De Gaulle had fired because they opposed pulling out of Algeria. The deal was done. Yet De Gaulle slapped down his interior minister for suggesting that Sartre be arrested: "You cannot imprison Voltaire," he ruled.

The French example did spread, worrying bureaucrats in Moscow as much as the ruling elites in the west. An unruly and undisciplined people had to be brought to heel. Robert Escarpit, a Le Monde correspondent, wrote on July 23 1968: "A Frenchman travelling abroad feels himself treated a bit like a convalescent from a pernicious fever. And how did the rash of barricades break out? What was the temperature at five o'clock in the evening of May 29? Is the Gaullist medicine really getting to the roots of the disease? Are there dangers of a relapse?... But there is one question that is hardly ever asked, perhaps because they are afraid to hear the answer. But at heart everyone would like to know, hopefully or fearfully, whether the sickness is infectious."

It was infectious. In Prague, communist reformers - many of them heroes of the anti-fascist resistance during the second world war - had that spring already proclaimed "socialism with a human face". The aim of Alexander Dubcek and his supporters was to democratise political life in Czechoslovakia. It was the first step towards a socialist democracy and was seen as such in Moscow and Washington. On August 21, the Russians sent in the tanks and crushed the reform movement.

In every west European capital there were protests. The tabloid press in Britain was constantly attacking leftists as "agents of Moscow" and was genuinely taken aback when we marched to the Soviet embassy, denouncing the invasion in strong language and burning effigies of the bloated Soviet leader, Leonid Brezhnev. Alexander Solzhenitsyn later remarked that the Soviet invasion of Czechoslovakia had been the last straw for him. Now he realised that the system could never be reformed from within but would have to be overthrown. He was not alone. The Moscow bureaucrats had sealed their own fate.

In Mexico, students took over their universities, demanding an end to oppression and one-party rule. The army was sent in to occupy the universities and did so for many months, making it the best-educated army in the world. On October 2 - with the eyes of the world on Mexico City 10 days before the Olympic games were due to begin there - thousands of students poured on to the streets to demonstrate. A massacre began at sunset. Troops opened fire on the crowd listening to speeches in one of the city's main squares - dozens were killed and hundreds more injured.

And then in November 1968 Pakistan erupted. Students took on the state apparatus of a corrupt and decaying military dictatorship backed by the US (sound familiar?). They were joined by workers, lawyers, white-collar employees, prostitutes, and other social layers, and despite the severe repression (hundreds were killed), the struggle increased in intensity and, the following year, toppled Field Marshal Ayub Khan.

When I arrived in February 1969, the mood of the country was joyous. Speaking at rallies all over the country with the poet Habib Jalib, we encountered a very different atmosphere from that in Europe. Here power did not seem so remote. The victory over Ayub Khan led to the first general election in the country's history. The Bengali nationalists in east Pakistan won a majority that the elite and key politicians refused to accept. Civil war led to Indian military intervention and that ended the old Pakistan. Bangladesh was the result of a bloody caesarean.

The glorious decade (1965-75), of which the year 1968 was only the high point, consisted of three concurrent narratives. Politics dominated, but there were two others that left a deeper imprint - sexual liberation and a hedonistic entrepreneurship from below. We had cause to be grateful for the latter. We were constantly appealing for funds from readers when I edited The Black Dwarf in 1968-69. One day a guy in overalls walked into our Soho office and counted out 25 grubby £5 notes, thanked us for producing the paper and left. He would do this every fortnight. Finally, I asked who he was and if there was a particular reason for his generosity. It turned out he had a stall on Portobello Road and, as to why he wanted to help, it was simple. "Capitalism is so non-groovy, man." It's only too groovy now and far more vicious.

In some ways, the 60s were a reaction to the 50s, and the intensity of the cold war. In the US, the McCarthyite witch-hunts had created havoc in the 50s, but now blacklisted writers could work again; in Russia, hundreds of political prisoners were released, the gulags were closed down and the crimes of Stalin were denounced by Khruschev as eastern Europe trembled with excitement and hopes of rapid reform. They hoped in vain.

The spirit of renewal infected the realm of culture as well: Solzhenitsyn's first novel was serialised in the official literary magazine, Novy Mir, and a new cinema took over most of Europe. In Spain and Portugal, ruled at the time by Nato's favourite fascists, Franco and Salazar, censorship persisted, but in Britain DH Lawrence's Lady Chatterley's Lover, written in 1928, was published for the first time in 1960. The book, in its complete form, sold two million copies.

Following Simone de Beauvoir's pioneering work in The Second Sex (1949), Juliet Mitchell fired off a new salvo in December 1966. Her lengthy essay, Women: The Longest Revolution, appeared in the New Left Review and became an immediate point of reference, summarising the problems faced by women: "In advanced industrial society, women's work is only marginal to the total economy... women are offered a universe of their own: the family. Like woman herself, the family appears as a natural object, but it is actually a cultural creation... Both can be exalted paradoxically, as ideals. The 'true' woman and 'true' family are images of peace and plenty: in actuality they may both be sites of violence and despair."

In September 1968, US feminists disrupted the Miss World competition in Atlantic City, warning shots in a women's liberation movement that would change women's lives by demanding recognition, independence and an equal voice in a male-dominated world. The cover of the January 1969 issue of Black Dwarf dedicated the year to women. Inside, we published Sheila Rowbotham's spirited feminist call to arms. (As I write this, Professor Rowbotham, now a distinguished scholar, has her job under threat from the ghastly, grey accountants who run Manchester University. We are now in an epoch of production-line universities with celebrities paid fortunes to teach eight hours a week and genuine scholars dumped in the bin.)

And, yes, there was also the pleasure principle. That the 60s were hedonistic is indisputable, but they were different from the corporatised version of today. At the time they marked a break with the hypocritical puritanism of the 40s and 50s, when censors prohibited married couples being shown on screen sharing a bed and pyjamas were compulsory. Radical upheavals challenge all social restrictions. It was always thus.

In the prefigurative London of the 18th century, sexual experiments required the cover of break-away churches such as the Moravians and surreal Swedenborgians (for whom "love for the holy" was best expressed in the "projection of semen"): both preached the virtues of combining religious and sexual ecstasy. Sexual orgies were a regular feature of Moravian ritual, according to which penetration was akin to entering the wounds in Christ's side. William Blake and his circle were heavily involved in all of this and some of his paintings depicting this world were censored at the time. I hope this does not come as too much of a shock to my old friend Tony Benn and others who sing Jerusalem without realising the hidden meaning of:

Bring me my bow of burning gold!

Bring me my arrows of desire!

Bring me my spear!

Homosexuality in Britain was decriminalised only in 1967. Gay liberation movements erupted with activists demanding an end to all homophobic legislation and Gay Pride marches were launched, inspired by the Afro-American struggles for equal rights and black pride. All the movements learned from each other. The advances of the civil rights, women's and gay movements, now taken for granted, had to be fought for on the streets against enemies who were fighting the "war on horror".

History rarely repeats itself, but its echoes never go away. In the autumn of 2004, when I was in the US on a lecture tour that coincided with Bush's re-election campaign, I noticed at a large antiwar meeting in Madison a very direct echo in a utopian bumper sticker: "Iraq is Arabic for Vietnam." The sound engineer in the hall, a Mexican-American, whispered proudly in my ear that his son, a 25- year-old marine, had just returned from a tour of duty in the besieged Iraqi city of Fallujah, the scene of horrific massacres by US soldiers, and may show up at the meeting. He didn't, but joined us later with a couple of civilian friends. He could see the room was packed with antiwar, anti-Bush activists.

The young, crewcut marine, G, recounted tales of duty and valour. I asked why he had joined the marine corps. "There was no choice for people like me. If I'd stayed here, I'd have been killed on the streets or ended up in the penitentiary serving life. The marine corps saved my life. They trained me, looked after me and changed me completely. If I died in Iraq, at least it would be the enemy that killed me. In Fallujah, all I could think of was how to make sure that the men under my command were kept safe. That's all. Most of the kids demonstrating for peace have no problems here. They go to college, they demonstrate and soon they forget it all as they move into well-paid jobs. It's not so easy for people like me. I think there should be a draft. Why should poor kids be the only ones out there? Out of all the marines I work with, perhaps four or five percent are gung-ho flag-wavers. The rest of us are doing a job, we do it well and hope we get out without being KIA [killed in action] or wounded."

Later, G sat on a sofa between two older men - both former combatants. On his left was Will Williams, 60, born in Mississipi, who had enlisted in the army aged 17. He was sure that, had he not left Mississippi, the Klu Klux Klan or some other racist gang would have killed him. He, too, told me that the military "saved my life". Following a stint in Germany, he was sent to Vietnam. Wounded in action, he received a Purple Heart and two bronze stars; he also began to change following a rebellion by black troops at Camranh Bay protesting racism within the US army.

Following a difficult period readjusting, Williams read deeply in politics and history. Feeling that the country was being lied to again, he and Dot, his companion of over 43 years, joined the movement opposing the war in Iraq, bringing their Gospel choir voices to rallies and demonstrations.

On G's right was Clarence Kailin, 90 years old that summer and one of the few remaining survivors of the Abraham Lincoln Brigade that had fought on the Republican side in the Spanish civil war. He, too, has been active in the movement against the war in Iraq. "Our trip was made in considerable secrecy - even from our families. I was a truck driver, then an infantry man and for a short time a stretcher-bearer. I saw the brutality of war up close. Of the five Wisconsinites who came to Spain with me, two were killed... later, there was Vietnam and this time kids from here died on the wrong side. Now we have Iraq. It's really bad, but I still believe there is an innate goodness in people, which is why so many can break with unworthy pasts."

In 2006, after another tour of duty, G could no longer accept any justification for the war. He was admiring of Cindy Sheehan and the Military Families Against the War, the most consistently active and effective antiwar group in the US.

A decade before the French Revolution, Voltaire remarked that "History is the lies we agree on". Afterwards there was little agreement on anything. The debate on 1968 was recently revived by Nicolas Sarkozy, who boasted that his victory in last year's presidential elections was the final nail in the '68 coffin. The philosopher Alain Badiou's tart response was to compare the new president of the republic to the Bourbons of 1815 and Marshal Pétain during the war. They, too, had talked about nails and coffins.

"May 1968 imposed intellectual and moral relaivism on us all," Sarkozy declared. "The heirs of May '68 imposed the idea that there was no longer any difference between good and evil, truth and falsehood, beauty and ugliness. The heritage of May 1968 introduced cynicism into society and politics."

He even blamed the legacy of May '68 for greedy and seedy business practices. The May '68 attack on ethical standards helped to "weaken the morality of capitalism, to prepare the ground for the unscrupulous capitalism of golden parachutes for rogue bosses". So the 60s generation is held responsible for Enron, Conrad Black, the subprime mortgage crisis, Northern Rock, corrupt politicians, deregulation, the dictatorship of the "free market", a culture strangled by brazen opportunism.

The struggle against the Vietnam war lasted 10 years. In 2003 people came out again in Europe and America, in even larger numbers, to try to stop the Iraq war. The pre-emptive strike failed. The movement lacked the stamina and the resonance of its predecessors. Within 48 hours it had virtually disappeared, highlighting the changed times.

Were the dreams and hopes of 1968 all idle fantasies? Or did cruel history abort something new that was about to be born? Revolutionaries - utopian anarchists, Fidelistas, Trotskyist allsorts, Maoists of every stripe - wanted the whole forest. Liberals and social democrats were fixated on individual trees. The forest, they warned us, was a distraction, far too vast and impossible to define, whereas a tree was a piece of wood that could be identified, improved and crafted into a chair or a table. Now the tree, too, has gone.

"You're like fish that only see the bait, never the line," we would mock in return. For we believed - and still do - that people should not be measured by material possessions but by their ability to transform the lives of others - the poor and underprivileged; that the economy needed to be reorganised in the interests of the many, not the few; and that socialism without democracy could never work. Above all, we believed in freedom of speech.

Much of this seems utopian now and some, for whom 1968 wasn't radical enough at the time, have embraced the present and, like members of ancient sects who moved easily from ritual debauchery to chastity, now regard any form of socialism as the serpent that tempted Eve in paradise.

The collapse of "communism" in 1989 created the basis for a new social agreement, the Washington Consensus, whereby deregulation and the entry of private capital into hitherto hallowed domains of public provision would become the norm everywhere, making traditional social democracy redundant and threatening the democratic process itself.

Some, who once dreamed of a better future, have simply given up. Others espouse a bitter maxim: unless you relearn you won't earn. The French intelligentsia, which had from the Enlightenment onwards made Paris the political workshop of the world, today leads the way with retreats on every front. Renegades occupy posts in every west European government defending exploitation, wars, state terror and neocolonial occupations; others now retired from the academy specialise in producing reactionary dross on the blogosphere, displaying the same zeal with which they once excoriated factional rivals on the far left. This, too, is nothing new. Shelley's rebuke to Wordsworth who, after welcoming the French Revolution, retreated to a pastoral conservatism, expressed it well:

In honoured poverty thy voice did weave

Songs consecrate to truth and liberty,

Deserting these, thou leavest me to grieve,

Thus having been, that thou shouldst cease to be.