The author and his colleagues have for several years used chess as tool for research intended to be relevant for the improvement of military command and control. The paper summarizes the main results from this research and also discusses the external validity of the findings. The major finding is that the ability to benefit from an information quality advantage - in terms of more current information or longer range of vision of the board - decreases as the information quality for both sides is reduced, even if the advantage is left unaffected. If this result from experiments with chess should be valid also for military command and control it would contradict a current hypothesis in that area which implies that military information systems do not have to deliver perfect information, it is sufficient if they can deliver more and/or better information than those of the enemy. This, in turn, would mean that measures other than investments in advanced information technology may be needed in order to establish superior command and control under conditions of imperfect information. It is finally concluded that findings from experiments with chess can have external validity if there is a theory connecting them to the target situation, and that there are no reasons to believe a priori that findings from abstract laboratory research have less external validity than findings from field studies in natural settings.