Combat simulations have typically used the simplifying assumption that combatants wear uniforms expressing their allegiance and their vehicles are appropriately marked. In Distributed Interactive Simulation (DIS) and its High Level Architecture (HLA) derivatives, this is represented by the force attribute: friendly, opposing, or neutral. Rules of Engagement (ROE) are restricted to the friendly side shooting the opposing side and vice versa. In today's asymmetric urban combat environments, this simplifying assumption is no longer valid. A common workaround has been to represent insurgents as neutral until they expose their weapons, at which time they switch their force attribute to opposing. However, the utility of this approach is limited, especially in cultures where weapons and militias are common. At the USJFCOM Joint Futures Laboratory, we are developing a new representation of sides and ROE for modeling asymmetric environments. We have incorporated a multiple sides representation and we differentiate between true allegiance and the uniforms or markings of the simulated entities. Other allegiances such as religion and tribe are captured with additional attributes. Simulated asymmetric opponents can attack as civilians or even as a side allied with the U.S. making ROE significantly more complicated. Now ROE and target acquisition have to deal with the recognition of aggression followed by the tracking and potential reacquisition of the perpetrators in a crowded environment. Fortunately, a number of experiments that study people's ability to perform these tasks are being conducted and models are being developed from them. The challenge of incorporating these more detailed models of target acquisition and ROE into urban combat simulations is exacerbated by the common use of force as a filter to support scalability, assuming that the friendly force only needs to monitor the opposing force and vice versa. Without that assumption new approaches are needed to deal with dense urban populations.