On digital twins in defense: overview and applications

Digital twins (DTs) have emerged as a transformative technology for modeling and simulation in various industries, including defense. This paper provides a comprehensive review of DT applications in defense modeling and simulation, focusing on how DTs can enhance simulation fidelity, interoperability, and decision support within defense systems. We consolidate existing research into a unified framework that links DT concepts, simulation-driven applications, and real-world deployments in defense scenarios. We discuss the role of the DT in applications like planning, training, execution, monitoring, and debriefing. We introduce a standardized DT characterization framework suitable for defense applications that aligns with industrial modeling and simulation standards and present a taxonomy of defense-specific use cases, highlighting recurring requirements. In addition, practical evidence is provided from a targeted questionnaire distributed to defense stakeholders and the ministries of defense (MoDs), revealing current challenges in DT integration and deployment. Finally, we conclude by identifying key gaps in DTs applications for defense modeling and simulation, including interoperability, security, and system integration, and we outline future research directions and development opportunities. This review aims to inform defense modeling and simulation practitioners and researchers, guiding future work on DT design, implementation, and deployment across defense applications.