What is the point of footnotes (or endnotes, as you call the ones at the end of the book)? It’s quite simple: they distinguish fiction from non-fiction.

Footnotes essentially establish a history book’s credentials. Footnotes tell the reader where the author found his or her information. They keep the historian honest because they make it possible for other historians to check his or her work.

And don’t think that that never happens. When I first started graduate school, a scandal rocked my department because a man who had recently gotten his PhD there published a sensational book about Nazis. One of his (and my) professors, who had spent decades researching the Nazis, did not agree with the book. So he traveled from California to the archives in Germany and found the document on which the student had based his entire thesis. It turned out that the student had missed the “not” in the sentence, which negated the thesis of his book. My professor always said that the point of the scandal was “never translate in the archives” but it also gave all of us a very healthy respect for footnotes.

But footnotes are also the friend of the researcher and writer. The footnotes in other people’s books will lead you to all sorts of interesting archives and books that you might not have found otherwise. They serve as signposts in a community of knowledge.

Footnotes also keep a writer organized. Say, for instance, that you are writing about an escape from occupied territory. There are a lot of people involved, various clandestine treks in the dark etc etc. It’s a complicated story. You have part of it written down, but life gets in the way in the form of a new job or move to a new home or some such. You have to put your writing down for months or even years. When you get back to it, you might want to know why you wrote what you did. Or, less dramatically, you might uncover a new document after you’ve already written part of your book. If you have footnotes you will know exactly which documents to re-read when you return to a particular section. Without the footnotes you are going to have to spend a lot of time looking for things.

Most importantly, without footnotes, your readers are going to wonder if you’re making all this up.

It’s sometimes hard to know what does or does not need a footnote. There’s no need to footnote facts that are common knowledge, such as the date of a military campaign or the name of a prime minister. You do need to footnote interpretations of those facts, especially if you’ve read a book that argues that the prime minister was actually a Nazi spy. And you need to footnote little known facts that you have found in archives, such as that Farmer X hid 18 aviators in his barn. You do not need to footnote your own interpretation of the documents you found in the archives, but other people need to footnote your interpretation after they read it in your book.