Towards the end of the war Walendy was drafted first into the Reichsarbeitsdienst (auxiliary force), then the Luftwaffenhelfer (child soldier in the air force) and finally into the regular Wehrmacht (the German military). He completed his Abitur (secondary education) in 1946 and then went to journalism school in Aachen. From 1950 to 1956 he studied political science at the Hochschule für Politik in West Berlin, where he received his diploma.
Afterwards he worked as the director of a folk high school in Herford and as the business leader of an employers' association in Bielefeld. In 1965 he went independent and founded the Verlag für Volkstum und Zeitgeschichtsforschung ("Publishing House for Folklore and Contemporary Historical Research") in Vlotho. In 1999 ownership of the publishing house was transferred to his wife, since Walendy was barred from directing it due to his criminal convictions. He maintains close contact with the Belgian revisionist organisation Vrij Historisch Onderzoek (VHO). He was imprisoned for 15 months for his writings denying the Holocaust.
Besides other works Walendy oversaw the publication of numerous materials in which the Holocaust was denied and the Third Reich was generally presented in a positive light. Among others these include:
- As early as 1964 he published his own book, Wahrheit für Deutschland – Die Schuldfrage des Zweiten Weltkriegs (Truth for Germany - The Question of Guilt for the Second World War), which in 1979 was listed by Germany's Federal Department for Media Harmful to Young Persons as material that could not be publicly advertised or given to young readers, due to the version it presented of the events that led to World War II. This restriction was lifted in 1994, after a long legal battle, on the grounds that Walendy's constitutional rights had been violated, since the federal constitutional court ruled that even a supposedly biased representation could be defended as an academic work. A renewed attempt to have the work listed was abandoned in 2001 due to a negative assessment of the chances of success in the event of another court case.
- Numerous copies of the historical revisionist magazine series Historische Tatsachen, which continues to be published by the Vrij Historisch Onderzoek (VHO) in Flanders. Its very first edition from 1974 contains a German translation of Richard Harwood's Holocaust-denying booklet "Did Six Million Really Die?".
- The German translation of Arthur Butz's book The Hoax of the Twentieth Century, in which the author attempts to discredit the evidence for the Holocaust.
- Atkins, Stephen E. (2009). Holocaust denial as an international movement. ABC-CLIO. pp. 108–109. ISBN 0-313-34538-4. Preview at Google Books.
- Die Literatur der Auschwitzleugner: Udo Walendy, Historische Tatsachen Nr. 26 Holocaust-Referenz: Argumente gegen Auschwitzleugner. (German)
- Much of this article is translated from the German wikipedia article of March 2nd 2007
- Original German mp3-speeches from Udo Walendy
- Personen: Udo Walendy Holocaust-Referenz: Argumente gegen Auschwitzleugner. (German)
- NPD: Raus aus dem Mief Der Spiegel, 29 November 1971. (German)