The authors were requested to present short papers giving opposing views on the subject of Guided Weapon Simulators. Much of this subject is now a matter of fact and the authors found themselves in agreement on far too many points regarding the present situation to follow the requested approach, and instead have adopted the method of writing a joint paper briefly reviewing the past history of simulation and setting out the present state of the art as they see it, leaving the discussion of probable future trends to encourage controversy. It has still been difficult to be controversial, but if some of the statements made stimulate discussion then a useful purpose will have been served. It may turn out that what the authors have found difficult to produce between themselves has been created only too readily between themselves and their audience.

It is not possible to discuss simulators without bringing in the concept of modelling, indeed an apt title for this paper could have been “From Simulation to Modelling”. The model technique has been defined as “a procedure in which a representation of a system is developed in some more convenient medium and checked to show that its behaviour agrees with that of the original system for a wide variety of conditions”.