This dissertation examines why some violent non-state organizations experiment with and develop a broader repertoire of tactics and targets to achieve their political goals while other groups consistently utilize the same methods across their lifespan. Social movement theory argues that challengers to the state's authority should continually innovate their repertoires of contention to mobilize support and sustain an effective challenge against the state; however, rebel groups vary markedly in the size of the tactical repertoires that they employ in their campaign to alter the status quo. Some non-state organizations are more capable of experimenting with and implementing new variations on existing methods than others.

I explore the factors that shape a militant organization's ``adaptive capacity.'' Specifically, these are the conditions that make an organization more or less capable of the incremental innovations necessary for expanding its set of violent repertoires and generating a larger tactical menu from which it can draw when selecting a strategy to challenge the state. The project first delves into how measure tactical adaptation, employing a text as data pipeline to classify and numerically compare descriptions of violent events. It then argues develops a theory of membership diversity as an internal driver of tactical adaptation. The theory emphasizes the stochastic elements that underpin membership interactions, arguing that individuals bring with them prior knowledge and experience when joining an organization and that knowledge diversity in an organization positively impacts an organization's adaptive capacity. The argument establishes two distinct mechanisms that focus on the endogeneity inherent to how solution concepts emerge and members learn in an organization.

The project directs the analytical focus on \textit{who} is in a violent organization and argues that the answer to this question can shape (a) the ultimate outcome of a civil conflict, (b) how analysts assess the military capabilities of an armed group, (c) other arenas for innovation, such as rebel governance or institution building, and (d) the underlying severity of the conflict. the theoretical framework advanced here atomizes the individual and thinks carefully about the information he or she possesses and how such information can operate contagiously in a closed system. Moreover, the theory generates a framework whereby individual-level interactions and outcomes contribute to larger organization-level outcomes that we observe. The theory reduces the concept of diversity down to its most basic element: information. This allows one to think about the impact of membership diversity more formally and to treat it as another resource that a violent organization has available to it.