A structured approach in system requirements analysis as applied for a project in the field of naval command and control systems is explained. In the layered approach, three types of analysis are described: user requirements analysis, process and information analysis, and technical system analysis, starting at a functional and operational level and resulting in a system-oriented level. It is demonstrated that the proposed approach can be used for system reengineering purposes. Based on the experiences with the project on the modernisation of the Tactical System of the Belgian-French-Netherlands minehunter, topics for future research in the field of integrated tool support, rapid prototyping, and development of command and control reference models are identified.