Pope Francis is to make two predecessors saints on Sunday, including Pope John XXIII, who saved thousands of Jews from the Holocaust and who was this week hailed by interfaith groups.

Ahead of what will be the world’s first double canonisation, media attention focused on the popular Polish-born Pope John Paul II, who died in 2005 and who also becomes a saint.

But to Jewish observers of the Vatican, the promotion of the man who served as head of the Roman Catholic Church between 1958 and 1963 was the more notable announcement. Primarily remembered for his various efforts during the Holocaust, it was only after detailed historical research that the full extent of Pope John XXIII’s efforts became known.

Born Angelo Giuseppe Roncalli in Italy, he worked as a papal diplomat in Eastern Europe before the war. He later used this experience to help save Jewish refugees from countries including Slovakia, Bulgaria, Hungary and Romania, helping many to escape arrest and deportation by Nazis, and to reach Palestine.

It led the International Raoul Wallenberg Foundation to recommend to Yad Vashem in 2011 that he be called ‘Righteous Among the Nations,’ but his influence was felt in the wider sphere of Christian-Jewish relations.

“As Pope, he removed the Good Friday prayer for ‘perfidious Jews’ and prayed for forgiveness for Christians who had mistreated Jews as cursed,” explained Rev. Patrick Morrow of the Council for Christians and Jews (CCJ).

“He also called the Second Vatican Council which issued a document that made it clear that responsibility for the death of Jesus could not be laid at the door of all Jews,” he said.

“When he once greeted a Jewish delegation to the Vatican warmly with ‘I am Joseph, your brother’, it is clear that he meant it.”