Never let it be said that David Irving has brought only evil into this world. True, his virulent anti-Semitism, his contempt for historical evidence and his irrational attempts to deny the Holocaust have caused considerable pain to many people; but his unsuccessful attempt to win a libel action against the academic Deborah Lipstadt in the spring of 2000 did also help create some extremely useful history books.
Three of the expert witnesses called in defence of Lipstadt wrote books as a result of the case: Richard Evans ( Telling Lies about Hitler ), Robert Jan van Pelt ( The Evidence for Auschwitz ) and Peter Longerich ( The Unwritten Order ). Of these three books, the shortest and most accessible is The Unwritten Order . It is also the most important of the three - arguably one of the most important books on the Holocaust that has ever been written.
(First published in 2001, it now appears in paperback, hence this belated review.) It is so valuable because it fills what had been a yawning chasm in Holocaust literature - a detailed analysis of Hitler's role in the decision-making process. Even today, Irving still peddles the nonsense that Hitler might not have been involved in the conception of the Holocaust - but no reasonable person could agree with that conclusion after reading Longerich's book.
Across 21 short chapters, Longerich patiently and with great clarity lays out Hitler's thinking about the Jews; from his statement at an early Nazi meeting in 1920 that "the effects of Judaism will never wane and the poisoning of the people will never end until the cause, the Jews, are removed from our midst"; to the last words he ever wrote, in his will and testament of April 29, 1945: "Above all I pledge the leadership of the nation and its followers to the scrupulous observance of the racial laws and to implacable opposition to the universal poisoner of all peoples, international Jewry."
Indeed, the lay reader who has had to endure some of the ill-informed comment around Irving's recent imprisonment in Austria for Holocaust denial - which implied that there was still the remotest possible doubt about the extent of the crime - will be surprised at the sheer weight of evidence that Hitler loathed and hated the Jews.
For the historian, the real debate has always been not over whether Hitler hated the Jews and wanted to "get rid" of them - that was obvious - but over the exact point at which the decision was taken that "getting rid" of the Jews meant not forced expulsion but extermination. Some historians have even suggested that there was never one moment of absolute decision, but rather that, via a process of "cumulative radicalisation" and a combination of initiatives from below and orders from above, the policy of extermination gradually evolved.
There will never be a definitive answer to this debate. Hitler was far too clever a politician to put in writing any order about this most sensitive of Nazi policies. But Longerich's book does persuasively suggest two key moments of escalation - one around the invasion of the Soviet Union in June 1941 and another in the immediate aftermath of the bombing of Pearl Harbor and the entry of the US into the war.
In particular, the speech Hitler gave to leading Nazi officials on December 12, 1941, five days after Pearl Harbor, seems to have been decisive.
Goebbels recorded in his diary at the time that "As far as the Jewish question is concerned, the Fuhrer is determined to make a clean sweep. He prophesied to the Jews that if they brought about a World War they would experience their own extermination. This was not just an empty phrase. The World War is here, the extermination of the Jews must be the necessary consequence."
The Holocaust happened, and Hitler played an important part in the decision-making process that created it. These two historical truths are as certain as the air we breathe. And we have Longerich to thank for laying out the evidence for these truths so calmly and professionally. And for making the resulting book such a compelling read.
Laurence Rees produced the award-winning BBC television series The Nazis: A Warning from History and is the author of Auschwitz: The Nazis and the 'Final Solution'.
The Unwritten Order: Hitler's Role in the Final Solution
Author - Peter Longerich
Publisher - Tempus
Pages - 254
Price - £12.99
ISBN - 0 7524 3328 8