This paper discusses a mixed initiative controller and testbed for Human Robot Teams (HRT) in tactical operations. We focus on a tactical operation that involves large teams of robots collaborating with one or more human agents, working collectively to achieve a common tactical goal. Our approach to HRT builds on earlier work in Mixed Initiative Control (MIC). The proposed proactive-MI approach allows the robots to assume or relinquish roles depending on their own capabilities and understanding of the environment. A key contribution to this research effort, and the focus of this paper, is the development of a HRT planning-execution framework and hardware-testbed to demonstrate HRT in tactical operations. The framework is built using software agents and Motion Description Languages (MDLe). The agent architecture provides the framework for collaboration, and communication, between the human agents and the robot agents. The framework is also designed to enable easy addition of both low-level robot drivers and high-level control algorithms/plans as are needed for a particular tactical operation. Metrics that are relevant to HRT in this particular domain are also presented.