As robotics and autonomous technologies continue to see breakthrough innovations, specifically in the areas of large-scale multi-robot teams, their alignment with operationally relevant applications in fielded contexts has been necessary to both obtaining valuable user feedback as well as informing and refining the use cases themselves, i.e., co-evolving the concepts of operations alongside technology maturation. The Defense Advanced Research Projects Agency (DARPA) OFFensive Swarm-Enabled Tactics (OFFSET) program1 was a four-year program which actively embraced this iterative, mission-focused development approach, coupling technology innovation with field experimentation activities to rapidly advance capabilities for large-scale, heterogeneous robotic teams in complex and adversarial urban environments. This vision paper highlights the motivation for the OFFSET program; provides descriptions of the technical objectives and outcomes; and offers insights into the program structure designed to facilitate and inject technology innovations through an ambitious campaign of field tests and learning.