New Vatican letter suggests Pope Pius XII knew about the Holocaust as early as 1942

• A newly-uncovered Vatican 1942 letter suggests that then-Pope Pius XII likely knew about Nazi genocide.
• The letter describes crematoriums and the mass murder of Jewish and Polish people.
• Pope Pius XII had already been scrutinized for his negotiations with Nazi Germany.

A letter published today by the Italian news outlet Corriere della Sera appears to confirm that World War II Pope Pius XII could have known details about the Nazi mass killings of Jewish and Polish populations as early as 1942.

While the relationship between Nazi top ranks and the Pope had previously been revealed, the Vatican argued that Pius could not have openly taken action against the mass killings because the Holy See couldn't verify they were taking place, according to historian David Kertzer's book "The Pope at War," as cited by The Guardian. But this new letter suggests otherwise.

This message is "the only remaining proof of a correspondence that likely took place over a long period of time," Giovanni Coco, the Vatican archivist who found the letter, told Corriere. The Vatican is thought to have received regular updates from Germany about the death camps.

The typewritten letter was authored by a German anti-Nazi Jesuit priest and sent to one of the Pope's top aides, Pius's secretary Robert Leiber.

Written in German, it opens with the line "Dear friend!" suggesting the two had a close relationship. It describes the use of crematoriums and mass murder in the Polish town of Rava-Rus'ka, now in modern-day Ukraine, where up to 6,000 people were killed. Thousands were transported to the death camp of Belzec in Nazi-occupied Poland. It also mentions the camps of Auschwitz and Dachau.

There's no proof that the Pope saw the letter — and the author, German Reverend Lothar König, urges caution and care against leaks to prevent the anti-Nazi network from being betrayed.

Pope Pius XII was afraid Hitler would win

The relationship between Pope Pius XII and Nazi leadership, especially Adolf Hitler, has long been uncovered and brought Pius under scrutiny, suggesting the pontiff was probably aware of Leiber's correspondence with König.

For example, during his annual Christmas speech in December 1942, Corriere notes Pius referred to "hundreds of thousands of people, who, without any fault, sometimes only because of their nationality or ancestry, are destined to die or to progressively be worn out."

Historians have debated whether Pius kept his silence out of fear, of complicity, or in an attempt to protect the Church during difficult times.

"Pius XII was afraid of, certainly in the first years of the war, that the Nazis were going to win. And so he felt he had to plan for a Europe that was going to be under Nazi control with their pal Mussolini helping out," David Kertzer told PBS last year.

The beatification process for Pius XII, which started in 1967, has been delayed because of his controversial choices during World War II.