The U.S. Army is seeking to accelerate the development of systems to counter near-peer adversaries in a multi-domain environment. To do so, the Army plans to leverage modeling and simulation to help guide its research, development, engineering and acquisition efforts. One particularly difficult modeling problem is estimating Soldier performance in a combat environment. To provide the required capability, the U.S. Army Combat Capabilities Development Command Data and Analysis Center is developing the Soldier and Squad Trade Space Analysis Framework (SSTAF). SSTAF is a software infrastructure system for integrating multiple human performance and other models to provide a unified representation of Soldier state, capability and behavior. SSTAF models the Soldier as a system, where the results of one model can affect the results of other models, and both the positive and negative effects of Soldier equipment can be captured.