David Frum: In the years between World War II and his capture by Israeli intelligence in Argentina in 1960, Adolf Eichmann had a great deal to say about his life and crimes. Can we begin by briefly explaining to readers: What is this material, how much is there, who collected it, and how does your use of this material differ from that of scholars and historians before you?

Bettina Stangneth: The answer is not so simple. I needed 600 pages to explain it, so perhaps I’m not the best person for a quick answer. But perhaps this will work:

My book is based on a wide variety of sources: newly discovered and previously examined documents from Eichmann and other Nazis from the Nazi era and from exile in Argentina, publications from the Nazi regime, and documents on postwar Germany from various intelligence services, press archives, and private estates. As an example, I read every single newspaper report from Eichmann’s trial. And there were over 800 books about Eichmann to be read. So most of the time there were no “hidden, secret, spectacular” sources—just hard work. As the saying goes: Sometimes “new material” is just “unused material.”

I found many unknown papers in the German archives. I got access to over 2,000 pages from the files of the German Intelligence Services. I found the private papers of the police officer Avner W. Less, who interrogated Eichmann in Israel. And I examined the papers of many other Nazis and Nazi sympathizers in Europe. We are talking about tens of thousands of pages here. Some of them were previously released, but not used or not used systematically. Others only resurfaced in 2009 through my research. It’s a big, cruel puzzle, spread over 30 archives.

The crucial component is the Argentina Papers. The Jerusalem court decided not to accept large parts of the so-called “Sassen Interview” as evidence because they couldn’t get proof of its authenticity. If the court didn’t accept a source it meant that the source wasn’t available to journalists. But that was not the main problem.

The prosecution was able to acquire around 700 carefully picked pages from the Argentina Papers, including 70 pages handwritten by Eichmann. However, nobody knew that it was only a part of a much bigger manuscript—it was absolutely impossible to recognize the real content of these fragments of a fragment of a manuscript. Think about your own writing. If I took some pages from the middle of one of your books, with the explicit desire to manipulate readers and hide the rest, it would be easy to mislead your audience. That’s exactly what Eichmann’s friend, Willem Sassen, did. Nobody was able to recognize the bigger picture. Today we have over 1,300 pages—along with marginalia from Eichmann—and we have much more information. This has changed a lot.

The Argentina Papers are the testimony of a group of Nazis who aimed to bring back the idea of National Socialism. Eichmann was a part of this group, consulted because of his firsthand knowledge of the “Jewish question.” The alleged “Sassen Interview” are the minutes of their meetings. Members of the group wrote their own drafts for discussions and Eichmann planned to publish his own book along with Willem Sassen’s book. We can reconstruct and synthesize these different manuscripts, transcripts, and papers. In short, the Argentina Papers provide a portrait of a radical Nazi group with incredible international connections and Eichmann’s thoughts and eloquence outside his glass box in Jerusalem.