Vatican archives on Pope Pius XII, the controversial wartime pontiff accused of failing to condemn the Holocaust, are to be opened next year after pressure from campaigners and historians.

Pope Francis announced the archives would be unsealed in March 2020, eight years ahead of schedule, saying the Roman Catholic church was “not afraid of history”.

His predecessor had been “criticised, one can say, with some prejudice and exaggeration”, he added.

The role of Pius XII, a staunch anti-communist who became pope in March 1939, six months before war engulfed Europe, has long been questioned by historians.

According to a display in Yad Vashem, Israel’s Holocaust memorial and museum, Pius “did not intervene” when Jews were rounded up and deported from Rome to Auschwitz.

His critics have also said he was enthusiastic about Adolf Hitler’s ascent to power and failed to stand up for priests who spoke out against the persecution of Jews and in many cases helped them and others escape being sent to Nazi concentration camps.

Pius’s public reticence over condemning the Holocaust was despite efforts by many in the church, as well as diplomats from allied countries, to persuade him to speak out.

Pope Pius XII in Berlin in 1927. Photograph: Hulton Getty

The Vatican has defended the wartime pope, who died in 1958, saying he used back-channels and quiet diplomacy to try to save lives.

Francis told staff at the Vatican archive on Monday: “The church isn’t afraid of history – on the contrary, it loves it, and would like to love it even more, like it loves God.”

Pius led the church during one of the “saddest and darkest periods of the 20th century”, the pope said. However, he added, he was confident that “serious and objective historical research will allow the evaluation [of Pius] in the correct light,” including “appropriate criticism”.

Pius’s papacy included “moments of grave difficulties, tormented decisions of human and Christian prudence, that to some could appear as reticent”. But they could be seen as attempts “to keep lit, in the darkest and cruellest periods, the flame of humanitarian initiatives, of hidden but active diplomacy”, said Francis.

In 2009, Francis’s predecessor, Pope Benedict, angered many Jews when he approved a decree recognising Pius’s “heroic virtues”, a first step toward sainthood.

Yad Vashem welcomed the Vatican’s decision to release the archives, saying it had been calling for years for the archives to be opened to “enable objective and open research as well as comprehensive discourse on issues relating to the conduct of the Vatican in particular, and the Catholic church in general, during the Holocaust”.

Iael Nidam-Orvieto, the director of Holocaust research at Yad Vashem, said it was known that Pius did not “publicly condemn the Nazis’ extermination of Jews in direct, clear and unambiguous terms”.

The Vatican may have operated a strategy of “public silence, with behind-the-scenes activity”, but available historical evidence had not confirmed that, she told Haaretz newspaper.

Rabbi David Rosen, of the American Jewish Committee, which has lobbied for more than 30 years for full access to the archives, said the pope’s decision was “enormously important to Catholic-Jewish relations”.

He added: “It is particularly important that experts from the leading Holocaust memorial institutes in Israel and the United States objectively evaluate as best as possible the historical record of that most terrible of times to acknowledge both the failures as well as the valiant efforts made during the Shoah [Holocaust].”

Naomi Di Segni, of the Union of Italian Jewish Communities, said she hoped the material in the archives would “further clarify the position of the church” during the Holocaust.

Six million Jews died in the Holocaust, many after being rounded up and deported to Nazi death camps.