Abstract: Modelling and Simulation (M&S) has had a profound impact on military training. Synthetic Environments replace the physical battlefield, equipment and environmental conditions. Semi-automated forces such as blue, red and white forces augment the interactive domains. While simulation-based training has been somewhat embraced as an acceptable alternative to utilising the real equipment or the conduct of major exercises, the underlying scientific principles of system abstraction, specification, development and validation have yet to be completely identified, defined and institutionalised as an engineering practice or academic discipline. This creates the essence of the shroud that covers this complex area of simulation. While we may possibly have faith in the entity the shroud covers, we need to reduce the semantic quagmire and the elevated expectations and underscore the faith with fact. This paper presents the current state of simulation as both a science and enabling technology for training.