Defence and security organisations rely on the use of scenarios for a wide range of activities; from strategic and contingency planning to training and experimentation exercises. In the grand strategic space, scenarios normally take the form of linguistic stories, whereby a picture of a context is painted using storytelling principles. The manner in which these stories are narrated can paint different mental models in planners’ minds and open opportunities for the realisation of different contextualisations and initialisations of these stories. In this chapter, we review some scenario design methods in the defence and security domain.We then illustrate how evolutionary computation techniques can be used to evolve different narrations of a strategic story. First, we present a simple representation of a story that allows evolution to operate on it in a simple manner. However, the simplicity of the representation comes with the cost of designing a set of linguistic constraints and transformations to guarantee that any random chromosome can get transformed into a unique coherent and causally consistent story. Second, we demonstrate that the representation being utilised in this approach can simultaneously serve as the basis to form a strategic story as well as the basis to design simulation models to evaluate these stories. This flexibility fulfils a large gap in current scenario planning methodologies, whereby the strategic scenario is represented in the form of a linguistic story, while the evaluation of that scenario is completely left for the human to subjectively decide on it.