01371nas a2200229   4500000000100000000000100001008004100002260000900043653001600052653002000068653002100088653002700109653001400136653002500150653001500175653002700190100001900217245003900236300001000275490000700285520084900292       2003                            d  c200310aacquisition10aDecision-making10adefence planning10aEvolution of modelling10aModelling10aOperational planning10asimulation10aTraining and Exercises1 aKlaus Niemeyer00aModeling and Simulation in Defense  a19-420 v123 a<p>Modelling and simulation are essential tools in defence planning, development and acquisition of systems, training and exercises, and operational planning throughout NATO and nations. In the article a contribution to a theoretical approach to the technology is provided, with discussion of definitions and characteristics, such as purpose of a model, reduction of complexity, and representation of real entities or systems. On the other hand, the defence applications are different in many aspects, e.g. objectives, time horizon, scenarios, data requirements, or reaction requirements, which leads to different utility of the model categories. Specific issues in modelling of the defence system are discussed, such as the military hierarchical structure, functional areas, operational phases, planning situations, and the decision cycle.</p>