At the request of the US Army Training and Command (TRADOC) Combat Training Support Directorate (CTSD), we examined the impacts of force modernization (new weapons, new sensor systems, and digitization of the battlespace) on the work trainers and analysts must do to support force-on-force exercises in live simulations. In 1997, we described tasks currently performed by trainers and analysts to support the simulation of system effects and provide post-exercise feedback to units at the Army's maneuver combat training centers. We estimated the effects of over 140 systems to be fielded over the next ten years on trainer workloads. In 1998 we interviewed personnel from the Army's National Training Center with handson experience supporting exercises involving a subset of the new systems during the Force XXI Advanced Warfighting Experiment (AWE). In the absence of interventions, force modernization will substantially increase the work required to support the simulation of weapon systems and provide formal post-exercise feedback. In addition, the same digitization capabilities that give units' information dominance over the enemy also have the side effect of making it more difficult for trainers to monitor exercises and track the flow of information within units.