The nature of urban warfare and the challenges of creating a reasonable and effective Red force for the urban environment are considerably different and divergent from the traditional and legacy approach in JSAF. This paper will address modeling an adaptive and challenging RED urban defense in support of the Joint Urban Operations Human-in-the-Loop (HITL) Experiment "Urban Resolve". The presentation will include a discussion of the challenges associated with aligning the Red force order of battle and simulation behavior requirements within the three phases of the experiment, developing the most cost effective approach to building the simulation code, and implementing a strategy for executing a war plan by a simulation cell. In the past, JSAF efforts have focused on fighting Cold War-type scenarios with fast-moving formations of armored vehicles rapidly crossing open terrain while engaging a similarly organized, equipped and trained opponent over several kilometers distance. Although recent events have shown the continued utility of such thinking, larger more densely populated urban areas may preclude such an approach to modern warfare, resulting in drastically reduced operational tempos and focusing on smaller areas of interest. This is especially true when facing a prepared and technologically advanced Red force. Recent events have also demonstrated effective low-tech alternatives for U.S. adversaries to apply in the confrontation of forces with superior technologies. The challenge for JSAF in Urban Resolve is carrying these ideas into the simulation environment, as well as applying them to an appropriate Red force.