By Gerard Noel
Continuum, £20

The title of Gerard Noel's new book about Catholicism's most controversial Pope seems to announce its conclusion before it has begun: that Pius XII (Eugenio Pacelli, who occupied the papal throne from 1939-58) failed to denounce Hitler or lead the Church in any opposition to Nazism. Yet it is also an attempt to redeem him.

Noel's goal, he says, is to understand Pacelli's "fragile psychology". He thinks that Pacelli, born to serve and not to lead, underestimated the political impact that the Vatican could have had in Germany and worried that Hitler would use any excuse the Church might give him to make things worse.

As Pope, Pacelli did not speak up for the Jews but then, he also did not speak up for Catholic victims of Nazi violence in Poland, even when begged to do so by Poland's president. And he did not speak out against the horrific killings by the Catholic Ustache partisans in Croatia, which even the Germans thought a trifle excessive.

He was probably a coward as well as an appeaser - though Noel denies this, on the grounds that early in his life, as papal nuncio in Munich, Pacelli had survived a challenge by Communist terrorists who put a gun to his head and demanded the use of his car.

The facts about Pius XII are contested but there is general agreement about his extreme conservatism. As a young legal assistant in the Vatican, he helped Pius X (1903-14) develop the legal "concordats" that helped the Church regain its lost power and influence. He also assisted in what Noel calls Pius X's "anti-Modernist witch hunts", rooting out modernising and heterodox tendencies within the Church. (Pacelli, significantly, had Pius X canonised in 1954 - the first Pope to be declared a saint in 400 years.)

What made Pacelli especially controversial is that, while insisting on the political neutrality of the Church, he was willing to back Fascism against Communism, even giving funds directly to Hitler in 1919 to back the fledgling Nazi party. He was also prepared to violate the fundamental human rights and freedoms of Catholics themselves if this meant advancing his own narrow definition of Catholic interests.

He evolved a Grand Design to erase inconsistencies in the Church's own legal system and strove, successfully, to change Catholicism into the totalitarian institution it now is, in which the Pope has absolute authority.

Noel does not exonerate Pacelli; he even accuses him of helping to cause both world wars. He blames the first of the new concordats - with Serbia -- for destabilising the Balkans and finds Pacelli complicit, 20 years later, in Hitler's preventing the Church - especially the popular, anti-Nazi Catholic Centre Party - from engaging in any political activity in Germany.

The future Pius XII grew up in an Italian Church culture where "loving" Jews meant loving them into conversion or persecution. In 1938, an encyclical he probably helped draft protested against Nazi violence against Jews but also blamed them for their own fate and warned the Church against becoming ensnared in secular politics.

After becoming Pope, he was willing to declare "warmth" and "friendship" towards the Nazi regime.

How is this excusable? Noel, who had a private audience with this Pope in 1948 and found him "awe-inspiring", argues that Pacelli, in spite of all the evidence to the contrary, was "a man of distinct compassion" who felt the Jews' pain but could not, by his own dubious principles, act to relieve it.

For Pius XII, the greatest possible disaster was the demise of the Catholic Church and this made the slaughter of millions of Jews (and Serbs and gypsies) secondary. And now some Catholics are trying to have him canonised.

Stephen Games is the editor of Sweet Songs of Zion, a history of the hymns of the Church of England