Based on the papers presented at a research seminar held in Lyon in 2022, this volume contains 11 contributions in French, English and German that represent various approaches to the social and cultural history of the Ptolemaic army from the first Lagid kings to Cleopatra VII. Some recent discoveries, both papyrological and archaeological, as well as new research on the surviving evidence in Greek and Demotic, shed new light on the military milieus of the Ptolemaic Empire. The studies combine a wide range of sources and approaches that add new perspectives on military control, the evolution of the judical and administrative system, and the socio-cultural relations between Hellenophone immigrants and natives in the Ptolemaic armed forces, which remains the most visible and dynamically growing aspect of the Lagid kingdom, a veritable “laboratory of mutations” of the Hellenistic world. The different topics covered in this volume include the system of cleruchic cavalry (military registers, horse training and competitions), the road network and mining in the Eastern Desert presenting a model of occupation very different from the Roman type, the social history of cleruchs (marriage strategies and identification of soldiers in Demotic sources), the evolution of one of the largest, but not yet sufficiently studied, immigrant communities in Hellenistic Egypt, the Thracians, and the much-discussed question of the fiscal aspects of the military.