This article discusses war diaries from World War II as historical sources and sheds light on their value for social historians. First, we discuss the importance of a good policy in terms of preservation and accessibility of the war diaries. Next, we situate war diaries as a specific genre within ego documents. We then show how war diaries can contribute to the historiography, using examples from the existing literature. Throughout the article, we draw from thirty Belgian war diaries to illustrate their potential uses. These war diaries were found in judicial files of collaboration cases.The full text of the article can be downloaded here as PDF. Open access licensed under CC BY. Use permitted with attribution. Copyright (c) 2025 Laura Nys, Bart Willems.(PDF) NYS & WILLEMS - "Het niet alledaagsche der toestanden" Dagboeken uit de Tweede Wereldoorlog als historische bron