Upgrading Defence capability involves much more than acquiring new hardware such as weapons or aircraft. This paper demonstrates how system dynamics modelling was used to assist in planning and management of the introduction into service of a new generation multi-role helicopter type. It describes the challenges of managing resources; and the complex interrelationships between tasks such as the training of pilots and aircrew, conducting maintenance on the aircraft and the achievement of defined levels of capability to conduct military operations. Whilst the modelling task focused initially on the management of human resources, it soon became obvious that complex dynamic problems are best addressed using a top-down approach, to achieve optimisation at the system level rather than attempting to optimise sub-systems. The modelling approach exploited trusted, functional modules of system dynamics structure rather than ab initio model construction. How this aided model construction and verification is described.