A simple act, it was the work of a few moments, but it triggered an epic era of political and religious convulsions that changed the shape of Europe. On 31 October 1517, a monk named Martin Luther walked to a church in the German town of Wittenberg and nailed a document – his 95 theses – to its wooden doors, lighting the fuse of the Reformation.

On Monday an ecumenical service led by Pope Francis at Lund cathedral in southern Sweden will herald a year of events running up to the 500th anniversary of the move that resulted in the greatest schism in western Christianity and a string of religious wars – and which has sectarian echoes today on the football terraces of northern Europe.

Christian leaders and congregations will spend the next 12 months consolidating moves towards greater cooperation and dialogue after centuries of division. In the first papal visit to Sweden in more than 25 years, Francis will lead prayers asking “forgiveness for divisions perpetuated by Christians from the two traditions”. On Tuesday, he will celebrate mass in Malmö before around 10,000 people.

In Germany, leaders of the Catholic and main Protestant churches have issued a joint text calling for a “healing of memories” of past divisions. An ecumenical pilgrimage to the Holy Land aimed at highlighting common roots despite separation has just concluded.

The commemorations are the latest step in a slow rapprochement between the Catholic and Protestant traditions – pursued by Francis, who has put ecumenicalism and healing past wounds at the heart of his papacy. The moves are not without controversy, however. “There are rightwing Roman Catholics who find the whole thing profoundly distasteful,” said Diarmaid MacCulloch, professor of church history at Oxford and author of The Reformation: A History. “But they’re the sort of people who hate the present pope anyway.

“On the other side, you’ve got the remnants of high-temperature Protestantism. In Northern Ireland, for instance, you’ll have preachers saying how dreadful all this is.”

A recent document signed by dozens of Protestant evangelicals and entitled “Is the Reformation Over?” says that although cooperation between the two traditions should be encouraged in areas of common concern, “the issues that gave birth to the Reformation 500 years ago are still very much alive in the 21st century for the whole church”.

The meeting of Pope Francis and Archbishop Antje Jackelén in Sweden will underscore one of the big divides between their churches: the role of women. Photograph: AFP/Getty

According to historians, Luther never intended his 95 theses – which may or may not actually have been nailed to the church doors – to spark a revolution. “He started by wanting reform. He never planned to split away from the Latin church; that wasn’t where it began,” said Bishop William Kenney, the Catholic co-chair of the international dialogue between Lutherans and Catholics, who will accompany the pope to Sweden.

Nevertheless, Luther’s theses, written in Latin, fundamentally challenged the authority and elitism of the Roman Catholic church. They were a backlash against increasing corruption and in particular the highly profitable sale of indulgences – promoted as fast-track tickets to heaven – to fund the building of St Peter’s Basilica in Rome. Luther declared that when it came to “justification” – avoiding hell, gaining admission to heaven – there could be no mediation, no brokering by the church. Salvation was a matter between an individual and God.

This was indeed revolutionary. Swiftly translated into German and other European languages, Luther’s ideas were the talk of Europe within weeks, spreading courtesy of the new printing presses – the Google and Twitter of the medieval era – and triggering religious, political, intellectual and cultural upheaval.

Rome condemned the monk as a heretic, removed him from the priesthood and banned his writings. In response, Luther publicly burned the papal bull, or edict. The sale of indulgences plummeted and his ideas started to take hold.

“It released something that still is important: a challenge to authority that has been good for the human community,” said Richard Holloway, the now agnostic former Anglican bishop of Edinburgh and author of A Little History of Religion, published this summer.

“It had a dark side, but it did move the religious debate on from divine authority imposed from above, and brought into the conversation a sense of protest against that. I think it would have happened in some other way even if it hadn’t been kicked off by Luther. Humans are revolutionary species that are constantly revising and challenging their institutions.”

Luther’s challenge to the once impregnable Catholic church was taken up by others, including John Calvin, whose ideas spread from Geneva to Scotland, France and the Low Countries. In Germany, the new ideas inspired the Peasants’ War of 1524-5. In England, Henry VIII –motivated more by lust and the desire for a male heir – embarked on his own, less clear-cut, separation from the Catholic church.

Rome launched a counter-reformation but by the end of the 16th century almost all of northern Europe was Protestant, albeit fractured into warring groups.

As well as bloodshed, the Reformation unleashed terrible destruction of religious heritage and art. In England, more than 800 monasteries, abbeys, nunneries and friaries were seized, libraries destroyed, manuscripts lost, treasures stripped and works of art appropriated. But the Reformation also gave rise to new forms of art, music and literature.

It’s the culmination of a great deal of work on the part of the Lutherans and the papacy over the past 20 years Diarmaid MacCulloch historian

“The dissolution of the monasteries was a tragedy,” said Holloway. “A lot of beauty was lost for ever. But it also released the power of the individual, the power of the small group, against the mighty institution. Loss and gain, that’s our story.”

The German priest and theologian at its centre was complicated, argumentative and bad-tempered, according to Nick Baines, the bishop of Leeds, who will tomorrow deliver a sermon about the Reformation in the monastery at Erfurt, central Germany, where Luther once lived as a monk.

“He said some terrible things about Jews,” Baines said, “which in turn had terrible consequences four centuries later. And he wasn’t exactly a proto-feminist. He was grasped by a concept of grace yet he didn’t exercise grace towards other people. He was a very brave man, but must have been a nightmare to be around. But most people who change the world are.”

It took Catholics some time to see the merits of the challenges posed by Luther, but the church needed reform, according to Kenney. “We had the problem of the sale of indulgences. There was a certain amount of corruption in parts of the church. I do think it was ultimately a good thing for the Catholic church – the Reformation, not the splitting of the church. It was forced to think again, to renew itself, and that is positive.”

Yet it took until 1999 for the Catholic and Lutheran churches to agree on a joint declaration that resolved many of the theological issues at the heart of the split. “That was an enormous step forward, and we’re now trying to work out what the consequences of that are,” added Kenney.

Popes John Paul II and Benedict engaged in some dialogue with the Lutherans and other Protestants, but Francis has really pushed it forward. “For 500 years, Europe has had this huge fault line between Catholics and Protestants,” said MacCulloch. “Now the pope is going to a Lutheran country to emphasise the division is in the past. It’s the culmination of a great deal of work on the part of the Lutherans and the papacy over the past 20 years.”

Francis had “softened the tone”, said Holloway. “The conversation will get warmer and sweeter, and who knows where it will lead. But the Roman Catholic church is a bit like a colossal aircraft carrier, and it takes a long time to make even tiny modifications.

“My hunch is that we’re probably moving to a stage where we’ll have the religious equivalent of multiculturalism. We won’t seek to merge, as it were, but we’ll seek to see the value in differences as long as they’re balanced with a sympathetic tolerance towards each other.”

From a Catholic perspective, Kenney said he thought there was a “realistic possibility” that the traditions could unite. “But there are big questions that need to be resolved,” he added.

Among those is the issue of women. Despite his warmth towards women members of the Catholic church and his frequent acknowledgement of the role they play in lay leadership, Pope Francis has insisted that “the door is closed” to women priests, although he has floated the possibility of female deacons.

The Lutherans have no such compunction. The Church of Sweden has had women pastors for more than half a century, the Danes for almost 70 years. And the gulf between the two churches on this issue will be underscored this week when Francis, the head of the Roman Catholic church, comes face to face with the head of the Church of Sweden, Archbishop Antje Jackelén – a woman.

KEY DATES

1517 Publication of Luther’s 95 theses arguing that salvation depends on faith alone

1521 Luther refuses to recant and is formally excommunicated by Pope Leo X

1522 His translation of the New Testament into common German gives ordinary people access to the scriptures and fuels criticism of the Roman church

1524 German peasants, partly inspired by Luther, rise up against feudal overlords

1526 Publication of William Tyndale’s English translation of the New Testament

1534 Act of Supremacy, making Henry VIII head of the church in England, heralds the English Reformation

1545 Council of Trent opens, to clarify doctrine and reform the Catholic church

1618 Revolt in Bohemia starts Thirty Years War across Europe

1648 Peace of Westphalia entrenches Protestantism in northern Europe, but the consequences of Luther’s revolt reverberate for centuries to come