Historians tend to view public health as a quintessentially modern phenomenon, enabled by the emergence of representative democracies, centralised bureaucracies and advanced biomedicine. While social, urban and religious historians have begun chipping away at the entrenched dichotomy between pre/modernity that this view implies, evidence for community prophylactics in earlier eras also emerges from a group of somewhat unexpected sources, namely military manuals. Texts composed for (and often by) army leaders in medieval Latin Europe, East Rome (Byzantium) and other premodern civilisations reflect the topicality of population-level preventative healthcare well before the nineteenth century, thereby broadening the path for historicising public health from a transregional and even global perspective. Moreover, at least throughout the Mediterranean world, military manuals also attest the enduring appeal of Hippocratic and Galenic prophylactics and how that medical tradition continued for centuries to shape the routines and material culture of vulnerable communities such as armies.