With the ever increasing complexity of warfighting systems in the Network Centric Warfare era, and the changing nature of the threats we face exemplified by the emergence of asymmetric warfare, maintaining the edge and achieving force transformation is ever more challenging. One of the many aspects of this challenge is ensuring that we identify the most appropriate training solutions for our warfighters. Current models provide guidance at the lower levels of individual training episodes but are found wanting in critical areas such as collective training and when trying to inform choices and make business cases when developing new capabilities. To address this problem we are developing a comprehensive and rigorous model of instructional environments, instructional methods and the nature of training tasks themselves in order to elicit a rigorous yet accessible method for identifying training solutions which meet the key characteristics of the demanding training problems that we face, whatever their scale. This paper reports on the outcome of the first stage of this work, which is the development of a comprehensive and robust model of the instructional environment. The model embraces actors, communication modes and channels, methods of encoding of stimuli and responses and the characterisation of key resources used in the instructional process. It forms the foundation for the characterisation of instructional methods and media, essential for the determination of key correspondences to the requirements of training problems which have to be supported if force transformation is to be achieved.