John XXIII But the world's bishops, led by a generation of outstanding European theologians, were in no mood to submit. They simply sidestepped the careful preparation and arranged their own agendas. The Curia were right to worry. What Pope John unleashed, now known as Vatican II, was the most momentous religious event since Martin Luther launched the Protestant Reformation 450 years earlier. ''It was a revolution,'' says American theologian John Markey. ''It was the most fundamental shift in self-understanding by the church in 1500 years. It is not over yet.'' The winds of change proved more like a tornado, leaving almost nothing untouched. It is difficult for people under 60 to grasp how radical, how wide-ranging and how deep the effects were because they do not remember the church as it was before the council - ''frozen in a time warp'', as Jesuit priest Gerald O'Collins told The Age.

Pope John intended the church to emerge from behind the battlements, lower the drawbridge and engage with the modern world. The most obvious and visible change for Catholics in the pew was worship in their own language rather than in Latin, with the priest now facing them rather than the altar, plus an affirmation of the role of laypeople. But there were other profound developments such as a willingness to engage with other churches, even other faiths, a renewed focus on social justice, and a decentralised approach to authority in the church. Today, as religious culture wars between traditionalists and progressives rack the church in the West, Vatican II has become the key battlefield. Both sides want to define and control the council's legacy. Progressives accuse traditionalists, who have had the huge political advantage of having the past two Popes among their number, of trying to wind back the liberalising reforms by stifling important debates and reimposing a strict top-down control of both practice and belief. Traditionalists counter that progressives want the church to conform to the ever-changing spirit of the times. ''Ratzinger (Pope Benedict XVI) has said they treated the church as if it were a haberdashery shop that has to update its window with the arrival of every new fashion season,'' says theologian Tracey Rowland, dean of Melbourne's John Paul II Institute for Marriage and Family.

''For my generation, this meant we had to sit around in class holding hands and singing Kumbaya. It was gruesome, especially for anyone intellectually inclined.'' That understanding of Vatican II ''wrecked the faith of a generation'', Rowland says. ''While Catholics were trying desperately to be modern, the rest of the world was becoming bored with modernity and turning postmodern.'' Others found the council and its fruits inspirational. For Bob Dixon, a teenager in Ballarat in the late 1960s, it connected his faith with the world. He was a child of the pre-Vatican II church, with its fixed certainties and emphasis on sin and grace, now often condemned as a fear-based approach to religion. ''But I suddenly began to see that faith was about life and the world and society and social justice,'' says Dixon, now one of the Australian church's most important laypeople in his position as head of the national Pastoral Projects Office. Young Australian priests who were in Rome for some of the sessions, such as George Pell - now Cardinal Pell, Archbishop of Sydney - and Michael Costigan, who began his later career as a journalist by posting home reports, were swept up in the enthusiasm.

Catholic confidence was high, Pell recalls. ''It was an enormously exciting time, a time of great intellectual ferment. We were caught up in this great movement of reform, and we were wildly over-optimistic.'' At the time, Costigan remembers, it was not only the Curia who doubted the need for a council. Things seemed pretty good: the seminaries were full and so were the churches. But the whole world was about to tilt on its axis. As Dixon observes, the council came at a time of huge social change: the rise of feminism, the sexual revolution, the shifting focus from community to individualism, a different attitude to authority and vastly greater opportunities for education. ''It happened just in time to enable the Australian church to ride out that turbulent time in the 1960s and '70s,'' he says. Cardinal Pell says: ''It changed the life of the church. It was an immense achievement. The change was not doctrinal but pastoral. When I speak to young Turks today who look back fondly to an idyllic church before the council, I point out some changes we take for granted.''

THE council met in four sessions from 1962 to 1965, and produced 16 documents, each a treatise - a manifesto, even - setting out the church's thinking and future direction in a specific area. Where before the church's official position was that all other churches were in schism and must return to Rome, the new stance emphasised dialogue and reconciliation. On other religions, the church for the first time welcomed what was ''good and true'' in them. There was a renewed emphasis on social justice as part of the Christian life alongside personal piety, and laypeople were explicitly recognised as having a central role in the mission of the church. Vatican authority was reduced in favour of a greater autonomy for local bishops and a more collegial approach. Pell identifies as particular advances the greater leadership role for bishops and also laypeople, whether on parish councils or church schools or welfare agencies. ''The introduction of ecumenism (openness to other churches) has been a wonderful blessing, even in Australia. Old Catholic-Protestant antagonisms have largely disappeared, and the tension now is between the Judaeo-Christian view and non-religious and occasionally anti-religious views.''

For Gerald O'Collins, back in Melbourne after 32 years teaching at Rome's Gregorian University - where he taught what are effectively a fifth of today's bishops and a third of the cardinals - the most important advances involved other religions and social justice. ''No council until [Vatican II] ever said a nice thing about Jews, Muslims or Buddhists. I can't tell you how much I welcomed the very short document on other religions. ''The Church in the Modern World led to justice and peace commissions around the world, and inspired people. In Rome I taught people who died for justice and peace in Africa and Central America. Maybe they would have done it anyway, but Vatican II gave it a major push. Justice and peace is not something you also do, it's at the heart of the faith.'' The increasing involvement of laypeople may have made the church's leadership uncomfortable, says Sydney theologian Neil Ormerod, but they have had to come to terms with it. Even theological education is increasingly in the hands of laypeople like himself. ''This is a development the hierarchy doesn't know what to do with. Lay theologians aren't under their control in the same way priests are. Nor do lay theologians necessarily have the same depth of spiritual formation and Catholic identity. Here at the Australian Catholic University we'd have about 40 theologians, of whom only three or four are priests.''

Over the half-century since Vatican II, the church hierarchy has wound back many of these radical changes, believing they have gone too far. This has led to the modern culture wars over such issues as authority and democracy, celibacy and married priests, the role of women and issues of sexuality. A recent example is the introduction of new English texts for worship, reinforcing the Vatican view of what worship should be, an imposition resented by many. Cardinal Pell, a leading conservative, dismisses the culture wars as all but won. ''There are pockets of idiosyncratic and possibly cranky resistance, and everything is not nailed down even now, but the battle is over. The real challenge now is to hand on the faith to young people and resist the rise of anti-religion.'' Progressives admit their cause is in decline at the Vatican, largely because the Pope appoints the bishops, and the last two Popes, covering 34 years, have been careful to favour conservatives who won't rock the boat. The progressives say the real life of the church is in the parishes (and welfare agencies), and that the bishops and even the Pope are largely unseen and irrelevant. Conservatives in contrast tend to look to Rome as custodian of Catholic belief and practice.

Melbourne publisher of religious books Garry Eastman regrets that the momentum for change has dissipated. ''People like myself in their 60s and 70s who lived through it see that the reform really stopped. There is no room for the free discussion that took place after Vatican II on the implications of science or biblical research. None of that has flowed down to the local level.'' Robert Blair Kaiser, who covered the council for Time magazine, suggests that ''rather than whine over what daddy won't let us do'', Catholics should be grateful for what the council did achieve, and build on that themselves. ''It has given us a new view of ourselves. It's made us more free, more human and more at the service of a world that Jesus loved. It has given us a new view of the church. It's our church, not the Pope's church, or the bishops' church, or a priest's church. It has given us a new view of our place in it. We can think, we can speak, we can act as followers of Jesus in a world that needs us.'' Barney Zwartz is religion editor.