"Those animals. I would like to throw some of those dogs under the tram."

Wilm Hosenfeld, the Nazi officer who famously saved the life of musician Wldyslaw Szpilman - an act commemorated in Roman Polanski's Holocaust film The Pianist - could not bear his anger towards his fellow soldiers.

The quotation comes from a revealing new biography of Hosenfeld, who was declared Righteous Among the Nations for saving Jews during the war.

German historian Hermann Vinke wrote the biography after meeting Hosenfeld's son, who gave him letters and diaries that his father wrote while based in Poland during the war. The documents reveal the depth of guilt and shame felt by Hosenfeld.

The book details how Hosenfeld used his position as head of sports to save lives by taking prisoners to work in stadiums he managed. It also features a letter written by 27 prisoners who thank Hosenfeld and call him "our father" for taking them to work in a gym and putting them out of reach of the death sqauds.

At one point, Hosenfeld wrote to his wife, Annamarie: "What cowards we are. Wanting to be better and let this to happen. For this we will be punished and later our innocent children too. With the mass-murder of the Jews we have lost this war… We have no right to mercy or compassion."

In an interview with the JC, Mr Vinke said: "Shortly after he joined the Nazi party in 1935, he asked himself why he became a part of such massive crime and destruction. I do not know of any other Nazi officer who wrote to such an extent on the war crimes of the Germans. I think that his Christian and moral values played a major part in it.

"The main message of my book is that we should always see the human being in front of us."

Andrzej Szpilman, son of "the Pianist", said that Hosenfeld's actions only highlighted the moral failure of other German soldiers. He said: "I read the new book. I think it reflects correctly the character of Hosenfeld. His character and actions show us that other Nazi soldiers had the possibility to aid Jews but chose not to do so. It further emphasises their evil."