This paper reviews the previous use of the term complexity with respect to weapon systems. It then moves past these dated inferences that weapon system complexity is merely a synonym for cost or technical challenge and establishes a formal definition of complexity based on the interactions between the entities comprising the system. Due to difficulties in direct measurement of interactions, an equation is introduced to calculate the theoretical maximum number of interactions and to use this as the measurement of complexity. Based on this definition, analysis of data for aircraft avionics and airborne reconnaissance sensors suggests convincingly that system complexity is indeed increasing exponentially. Increasing complexity can be linked to system development cost and schedule and production cost as previously inferred by at least some researchers. No single solution exists for addressing this trend of increasing complexity. Attempts can be made to either limit the amount of complexity of future weapon systems while still providing adequate performance increases or to better cope with complexity. In regard to the latter, it has been suggested that acquisition is analogous to Clausewitzian warfare in some key respects and that the cultivation of acquisition genius should be pursued in like manner to the cultivation of war genius.
