Situation awareness (SA) is a prerequisite to timely and accurate decision-making in the fast and highly stressful context of infantry operational environments. The introduction of electronic support technologies onto the battlefield is expected to improve SA by providing the right information, at the right time, and in the right format. In the cur rent paper, we report a systematic and innovative approach to the design of portable SA support systems (P-SASS) that combines the use of human and computer agent simulation, non-intrusive objective metrics and cognitive system engineering to assess the benefits of such systems to the tactical commander. The prototype of a P-SASS designed to improve positional SA is compared to the traditional map and radio communication procedure in a simulation involving subject matter experts (SMEs) and using Virtual Battle Space 2 within the Thales Battle Transformation Center. Dynamic measures of performance, SA probes, and usability questionnaires were used in order to assess the improvement in SA associated to the P-SASS. The results suggest that i) the P-SASS increased awareness of positioning; ii) participants' confidence in their own SA was well calibrated when using the system; iii) responsiveness seem to benefit from the use of the P-SASS. Furthermore, this study also provides usability insights into the cur rent design process, and validates a methodology that can serve various initiatives of SASS development and evaluation.