This paper explores the application of Circular Economy (CE) principles to enhance the supply of Unmanned Surface Vessels (USVs) to the defence market. It investigates the advantages of using USVs for maritime operations, especially in conflict regions, highlighting their compact size and versatility, enabling them to execute critical missions. The implementation of CE principles in USV design encourages improvements in sustainability, availability, and suitability for diverse mission requirements, aligning with the UK defence capability network's focus on equipment upgrades for enhanced readiness. The paper investigates how CE principles can reduce production lead times, improve operational availability, and offer broader benefits to both defence customers and Small and Medium Enterprises (SMEs), focusing on five key metrics: recyclability and repair, minimisation of waste and emissions, optimisation for longevity, decrease in part count, and design for disassembly.