New Research Explores the Leper Knights of Saint Lazarus as an Early Case of Bioterrorism

New Research Explores the Leper Knights of Saint Lazarus as an Early Case of Bioterrorism

A new interdisciplinary study published in the *Defence and Technical Bulletin* offers a compelling reinterpretation of one of the most unusual military institutions of the Crusades: the Military and Hospitaller Order of Saint Lazarus, composed largely of knights afflicted with leprosy. The research, conducted by Gian Marco Ludovici, Paola Amelia Tassi, Alba Iannotti, Colomba Russo and Andrea Malizia from the University of Rome Tor Vergata, positions the Order as a historical example of pre-modern bioterrorism rooted not in disease transmission, but in the strategic use of psychological impact.

The paper examines how biological threats in pre-modern warfare—ranging from the well‑documented siege of Caffa to less formalized uses of disease—must be understood within their broader social and cultural environments. In the case of the Order of Saint Lazarus, the study argues that the Knights’ operational effectiveness derived not from the contagiousness of *Mycobacterium leprae*, which is comparatively limited, but from the symbolic and emotional force associated with leprosy in medieval society.

According to the authors, the deployment of leper knights on the battlefield represented a calculated form of psychological warfare. Medieval populations often interpreted leprosy through a theological and moral lens, associating it with impurity, divine punishment and social exclusion. When leveraged in military contexts, these associations elicited fear, disorientation and moral shock among opposing forces. This dynamic, the study suggests, reveals an early institutional understanding of asymmetric warfare in which societal disruption, rather than pathogen lethality, produced the decisive advantage.

By situating the Order of Saint Lazarus within a broader historical continuum of biological and psychological strategies, the article highlights a core principle of modern bioterrorism: the exploitation of cultural vulnerabilities surrounding disease can disproportionately amplify the impact of a biological threat. As the authors note, even in contemporary settings, the perception of a pathogen—shaped by misinformation, cultural narratives and societal anxieties—can be as consequential as its biological properties.

The conclusions of the study underline the relevance of historical cases for present‑day CBRNe preparedness. The authors advocate for integrated defence strategies that address not only the material risks posed by biological agents, but also the informational, cognitive and social dimensions that influence population behaviour during crises. Strengthening risk communication, managing public perception and building societal resilience are identified as essential components of modern counter-bioterrorism frameworks.

The publication enriches the growing body of research on the historical roots of CBRNe threats, offering valuable insights into how cultural constructs of disease can be operationalised for strategic purposes both in the past and today.

For readers interested in the intersection of history, public health and security studies, the article provides an innovative perspective on how medieval practices continue to inform contemporary approaches to biological risk assessment and management.

Ludovici, G. M., Tassi, P. A., Iannotti, A., Russo, C. & Malizia, A. (2026). ‘The Leper Knights of Saint Lazarus: A Case Study in Pre-modern Bioterrorism During the Crusades’, Defence and Technical Bulletin, Vol.1, pag. 140-146