Many people in the Netherlands loathed the German occupier. Soon, the need to put this loathing into print arose. In this way, the members of the resistance also tried to invoke and stimulate a spirit of resistance and a will to fight in large groups of the population. This resulted in a lot of material being printed in secret. In secret too, and with all the risks it entailed, the material was circulated. The number of copies of these illegal publications and the way they were circulated were quite varied.

Merely to have such illegal or clandestinely produced publications in one's possession was punishable. Therefore, it is remarkable - and historians may count themselves lucky - that much of this material has come down to us.

After the war, Dr L. de Jong headed the NIOD. Dr De Jong and his co-workers repeatedly called on the population to hand over this kind of material to the Institute. The appeal got a wide response. This way, a noticeably wide-ranging collection could be brought together. Even now, relevant additions to the collection are donated or left to the institute. This means that, with the passage of time, more documents might be available for reference at the Institute than can now be viewed on this website.