AbstractThe process of designing complex, costly military systems benefits substantially from analyses of performance as predicted by some form of model of the system and its operating environment. In this paper, techniques are described that have been implemented in a suite of computer programs to represent the tactical situations that can develop between two opposing submarines. The kernel of the program suite is the Submarine Interactive Attack Model (SIAM). This is sufficiently versatile that a wide range of scenarios can be simulated, and meaningful statistics for expected submarine performance obtained. Emphasis is placed on the modelling of both the dynamic tactical situations that can evolve in underwater warfare and the tactical decision-making that influences the outcome of submarine operations. Although the techniques have been applied to a specific domain it is believed that they are applicable to a wide range of complex problems.