Pope Francis goes to Sweden on Monday to help start commemorations of the 500th anniversary of Martin Luther’s Reformation, a trip that has won him praise from Lutherans but criticism from Catholic conservatives.

Martin Luther, a German, started the Reformation in 1517 when he wrote 95 theses criticizing the Catholic Church for corruption in Rome, including the buying of ecclesiastical privileges, nepotism, usury and the selling of indulgences.

It led to a violent, often political schism throughout Europe and Christianity, prompting among other things the 30 Years’ War, the destruction of English monasteries, and the burning of numerous “heretics” on both sides.

Francis is traveling to the southern Swedish city of Lund, where the Lutheran World Federation was founded in 1947, for a joint service with Lutherans to launch Reformation commemorations that will continue throughout the world next year.

On Monday Francis and Lutheran leaders will hold an ecumenical prayer service in Lund’s Lutheran cathedral and another inter-religious event in nearby Malmo.

Last January, Francis, who is keen to continue Catholic-Lutheran dialogue, asked Protestants and other Christian Churches for forgiveness for past persecution by Catholics.

Conservative Catholics believe their Church has conceded too much to Lutherans and should not be taking part in any event that praises Luther.

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