In a gesture of reconciliation rich in symbolism, Pope Francis flies to Sweden on Monday for the start of celebrations marking the 500th anniversary of the Reformation.
"What's to celebrate?" Catholic conservatives cried when the visit was announced in January, the negative reaction perhaps helping to explain why the visit has been belatedly extended for a day so that it can include a papal mass.
Francis was initially scheduled to make only a one-day visit to Lund in southern Sweden to attend an ecumenical service of commemoration jointly organised by the Lutheran World Federation (LWF) and his own inter-faith agency.
The service will see Francis worship alongside the heirs to a tradition founded in fervent opposition to the teachings and power of the church of Rome.
Against that historical backdrop, Francis's presence in Lund will be "quite simply sensational", according to Theodor Dieter, of the Lutheran Institute for Ecumenical Research.
"It must not be forgotten that (Martin) Luther himself described the pope as the Antichrist and was a severe critic of the Roman Catholic Church," Dieter told AFP.
"Only three years ago, the bishops and cardinals did not think that the Reformation was a subject for celebration."
History is not the only issue that separates the two traditions.
The Swedish branch of the Lutheran Church is among the most liberal in the Christian family.
Its top archbishop has been a woman, Antje Jackelen, since 2013; it has ordained women pastors since 1960 and embraces homosexuality to the point of having openly lesbian and gay bishops - all unimaginable in the Catholic Church.
Francis however has championed rapprochement between Catholicism and all other faiths, saying earlier this year that Catholics should seek forgiveness for their past treatment of other Christian believers, and vice versa.
"We cannot undo what happened but we cannot allow the weight of the mistakes of the past to poison our relations," he said.
The LWF's president, Bishop Munib Younan, echoed that sentiment. "Being a Lutheran of course, I also carry the burden of the past," the Palestinian Christian told AFP.
"But I don't want the burden of the past to define my future."
Legacy of deep mistrust
The service in Lund will take place exactly one year before the 500th anniversary of German monk Martin Luther nailing his famous written protest against the Church's abuses of its power to the door of a church in Wittenberg.
The act of defiance of papal authority resulted in Luther being excommunicated and declared an outlaw by Rome.
Some Lutherans would like the excommunication order posthumously annulled but the Vatican's doctrinal experts have repeatedly said that cannot happen.
The posting of the "95 theses" is considered the starting point of the Reformation - a dissenting movement that created a religious and political schism in Europe.
This took centuries to fully unfold and featured many violent episodes before Protestant churches established themselves as the dominant form of Christianity across most of northern Europe.
Security and police preparations underway in front of Lund's Cathedral in southern Sweden where the Royal family will welcome Pope Francis. (AAP) Source: AAP
The numerous conflicts created a legacy of deep mistrust which has only recently started to break down.
The Lund event is part of a 50-year dialogue in which the Lutheran and Catholic churches are attempting to agree on a common account of the painful events of the reformation.
The two Churches agreed in 1999 on a joint statement addressing the theological issues at the root of the upheaval.
These included questions such as whether humans could earn their place in heaven through good deeds or whether salvation comes exclusively through the grace of God.
Luther and his followers championed the Bible's translation into local languages and its status as the sole source of divine authority - effectively challenging the authority of the Catholic hierarchy.
They opposed the sale of indulgences and other forms of clerical corruption and challenged notions such as the idea of penance, the veneration of saints, the existence of purgatory and the infallibility of popes.
Irreligious
Polls show Sweden, nominally Lutheran, is one of the world's most irreligious nations. In a WIN-Gallup survey last year, around eight in 10 Swedes said they were either "not religious" or "convinced atheists." Surveys show Swedes trust institutions like the tax agency more than the Lutheran Church.
An atheist cemetery opened this year, where Swedes can be buried without religious symbols like the cross, star of David or Islamic crescent.
David Thurfjell, professor of religion and history at Sodertorn University, said for many Swedes it may be easier to come out as gay than to come out as religious.
"Swedes are just uneasy with the word," said Thurfjell. "You would just never call yourself religious."
It is a trend seen across the Nordics. After making it possible to exit from membership on-line, Norway's Lutheran state Church saw 25,000 people exit in August, the biggest one-month drop in its history.
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Swedes still take part in Christian sacraments such as baptism and many still pay small voluntary tax contributions to the Lutheran Church of Sweden.
Some also say that a wave of new immigrants - many Christians and Muslims who have fled war in the Middle East - is changing attitudes. Around 17 percent of Swedes are now foreign-born.
"It has been secularized for so long, that people start to get tired and sick of it," Sweden's only Catholic archbishop, Anders Arborelius, said. "The new situation with a massive immigration of people who are often more religious has also changed the mentality."
Multi-culturalism has challenged Sweden's comfortable secular identity. This year Sweden faced controversy when former schools minister Aida Hadzialic, herself an immigrant, said religious schools that separate boys from girls should not be allowed.
That backlash against any perception of religious interference may mark rancis's visit.
"I hope they'll [Swedes] be opposed to the Middle Age dogma the papacy represents," former ABBA band member Bjorn Ulvaeus and member of Sweden's Humanist Association said in an email. "But, I fear, they'll be mostly indifferent."
- with Reuters
