‘REPMUS’ (Robotic Experimentation and Prototyping augmented by Maritime Unmanned Systems) is a Portuguese Navy (PN)-led, NATO co-hosted exercise – held each September off Troia, southern Portugal – focusing on maritime unmanned system (MUS) capability development. As NATO requirements to improve presence, mass, and capability at sea to offset Russian activity become more pressing, ‘REPMUS’ is stepping up from test and evaluation activity to OPEX-based development of MUS capabilities for integration into NATO task groups.