Eugenio Pacelli was the Vatican ambassador to Germany. He HATED NAZISM. He had to do all that he could do without fanfare or publicity because when the Church made a stand against the Nazi’s the Jews and Catholic priests suffered imprisonment and execution as retribution. Edith Stein, a Jewish convert and Carmelite Nun was killed in Auschwitz in 1942, as revenge against the Church for speaking against the Nazis.
The Jews themselves begged the Church not to oppose the Nazis publicly. So, not being stupid, Pius XII did all he could do for the Jews and other Nazi enemies secretly. You can read about this Here–>Edith Stein
But the most incontrovertible evidence that Pius XII helped the Jews is the story of the Chief Rabbi of Rome, Israel Zolli, and his conversion to the Catholic church less than a year after Rome was liberated by the Americans. And not only that, he chose as his baptismal name, EUGENIO, the name given to the Pope by his parents.
A few days later, the Chief Rabbi relinquished his duties, and went to find a priest in order to complete his instruction in the truths of the faith. On February 13, 1945, Archbishop Traglia conferred the sacrament of Baptism on Israel Zolli, who chose ‘Eugenio’ as his Christian name, in gratitude to Pope Pius XII for his decisive action on behalf of the Jews during the war. Zolli’s wife, Emma, received Baptism with her husband, and added the name ‘Maria’ to her first name. Their daughter Miriam would follow her parents after a year of personal reflection.
You can read the rest of his amazing conversion story at Salvation is from the Jews
There you will find many Jewish conversion stories. The webmaster’s own story is told in great detail in his book Salvation is From the Jews
I would also recommend Honey From The Rock a book of Jewish conversion stories.