When Benedict XVI ascended to the papacy after the death of Pope John Paul II in 2005, world Jewish leaders were nervous about the new German-born pope.
Joseph Ratzinger had joined the Hitler youth as a 14-year-old and went on to serve in the German military, as six million Jews were sent off to the death camps. Though Benedict was eventually exonerated and even embraced by Jews -- he called the Holocaust a "dark time" in his life -- his German past continued to haunt him.
"When he was elected pope a lot of alarm bells went off in the Jewish community," said Rabbi Marvin Hier, founder and dean of the Simon Wiesenthal Center in Los Angeles, who had a one-hour private audience with Benedict when he became pope. "First, it was about the Nazi aspect."
The Wiesenthal Center launched an investigation into Benedict's role in the Third Reich only to discover the Ratzingers came from a family of anti-Nazis, with no hint of antisemitism.
"The fact that he was in the Hitler youth -- if you were a young child during the Third Reich and you didn't go, you'd be condemned," said Hier. "He didn't volunteer. That's not a blemish. We've done a bunch of research, and that should be very clear."
But the role of the Catholic Church and most particularly the silence of Pope Pius XII, who served from 1939 to 1958, as millions went off to the gas chambers has dogged Benedict, despite being viewed as a friend by those who are Jewish.
Both Pope John Paul II and Benedict pushed for Pius to gain sainthood. In 2009, as Pius moved toward beatification, the Vatican issued a statement that the church was looking at his "Christian life" as a whole and not "the historical impact of all his operative decisions," according to The New York Times.
Moving Pius toward sainthood "is in no way to be read as a hostile act towards the Jewish people, and it is to be hoped that it will not be considered as an obstacle on the path of dialogue between Judaism and the Catholic Church," wrote the Rev. Federico Lombardi, a Vatican spokesman.
"Pope Pius XII didn't care much about Jews. He was the pope of silence," said Hier.
"They say [Pius] looked at Hitler as a mad man, and if he had opposed him publicly, it would have destroyed the Catholic Church. It was against everything the Christian Church stands for," said Hier.
"In Auschwitz, ten to fifteen thousand people were gassed every day," he said. "Priests and local parishes knew what was happening and the bishops reported to the Vatican."
The Vatican has always denied that Pius ignored the plight of the Jews and Benedict said the Pius worked "secretly and silently" to help Jews.
In 2007, Jewish leaders criticized Benedict for lifting restrictions on the old form of Latin mass, which included prayers for Jews to "be delivered from their darkness" and converted to Catholicism.
According to press reports at the time, Benedict said he had decided to allow celebration of the traditional mass if a "stable group of faithful" requested it. The more liberal Second Vatican Council had allowed mass to be performed in vernacular languages in the 1960s.
Matthew Bunson, editor of The Catholic Almanac and Catholic Answer magazine and author of the first English-language biography on Benedict, "We Have a Pope! Benedict XVI," said the pope had been a "source of controversy and investigation and initially made the world Jewish community uncomfortable."
"But today Jewish leaders have a solidified and strong relationship with the head of the Catholic Church," he said.