The CATS TCT is a military wargaming simulator used by the Swedish Armed Forces for education of position holders within battalion or company staffs. The CATS TCT was developed during the nineties and one of the challenges today is how the system can be modernized in order to meet the increased demands on usability. This master thesis is part of the work with modernizing the CATS TCT and a usability study has been conducted in order to identify issues and problems of the current system related to usability. This thesis is conducted at BAE Systems C-ITS in Linköping and the main focus of this study has been how to analyze and re-design the CATS TCT in order to enhance the usability of the system. Empirical data in this study has been collected through six semi-structured interviews, one observation and two focus group interviews and the result of this study has elicit several problem areas related to any of following usability aspects: effectiveness, efficiency or satisfaction. The conclusions from this investigation is that the CATS TCT simulator is an valuable and appreciated educational tool – especially from an effectiveness point of view. When it comes to efficiency, however, several problems areas has been identified and these areas are: information architecture, interface interaction, how orders are issued to units and how the simulation rules are implemented. When it comes to the users satisfaction of the system no unequivocal conclusion has been possible to present. As a complement to the identified issues and problems of the simulator this study has also presented examples on how prototypes could be used to solve some of the identified problems. More specifically, in this report re-design solutions related to how the users interact with the map, how orders are issued and how status overview is displayed has been presented.