This Element presents an analytical model for assessing the success or failure of innovative large-scale defence projects. To achieve this goal, it constructs a theoretical model based on a three-angle analysis: the International System, the innovative potential, and the domestic political arena. Each angle of analysis generates an independent variable, namely: level of threat, technological feasibility, and political consensus. It is held that technological feasibility and political consensus are necessary and conjointly sufficient conditions to explain the success or failure of large-scale defence projects. The success of the innovative defence projects is strongly and positively related to the level of external threat. The initial hypothesis is tested by scrutinizing three specific projects in the United States (Future Combat Systems, The B-2 Stealth Bomber and the F-35). The conclusion is that the model is sound and might be generalized to analyse the prospects of success or failure of other large-scale defence projects.