Historical research is a little like hunting. You need to know what kinds of tracks your quarry leaves; it always helps to have a local guide, and timing makes all the difference.

For the most part historians follow paper trails, so we have to think about who would have written about our subjects and why. For instance, the men who wrote the Treaty of Versailles wrote all sorts of official memos, reports and proclamations that were diligently preserved by their governments. It’s a matter of notorious common sense, however, that resisters did not write things down and that the Gestapo burned their files.

But it turns out that common sense is wrong. Resisters didn’t write down much during the war, but they did generate a good deal of documentation after the war. Broadly speaking, it falls into two categories: investigations conducted by government agencies and applications for benefits. The American and British militaries, for instance, wanted to know who had helped allied airmen in order to reward those helpers. The French army wanted to know what had gone on in France during the war for reasons of internal security. They all detailed men to find and interview resisters immediately after the war and then they filed away their reports.

In the following decades, many resisters applied for one government pension or another. One needed to prove one’s bona fides as a resister to get such benefits so the dossiers often (although, maddeningly, not always) include at least some information about Resistance activity. Now, I’m not one to wish bureaucratic hassles on anyone, least of all the survivor of a concentration camp, but as an historian I have to say that troubles with bureaucrats create a lot of documents. For instance, a French woman who served as a courier in Dutch-Paris encountered difficulties because she missed the deadline for the medical care that she desperately needed after returning from Ravensbruck. Her application led to a police investigation including interviews of witnesses and more details than most such dossiers. (It turned out well: she got the medical care and I got the information.)

But even if you know who was writing about your historical quarry, it’s not always clear where the documents would be. That’s where a local guide becomes invaluable. I’ve recently had the great good fortune to have the help of Capitaine Stéphane Longuet of the Service historique de la Défense, Bureau Résistance in Vincennes, outside of Paris. He and his very friendly staff not only allowed me to see over a hundred personal dossiers but found other files for me that I would never have found on my own simply because I did not know that certain military agencies had made these particular investigations in the late 1940s. My most sincere thanks to them for their generous assistance.

One set of files that the Capitaine called out of the labyrinths of the army’s archives particularly illustrates the importance of timing. They came from a counter-espionage agency and involved a German spy from the Abwehr. Thanks to the lapse of time and the French archival law of 2008, I’m the first researcher to see them. Even five years ago I never would have even known that they exist. I almost didn’t mind that they didn’t have what I was looking for, it was so thrilling just to see them.