Deploying Troops.
Duncan had never formally studied military tactics; all his skills in deploying formations were accumulated from playing total war type games in his previous life. If you asked him to explain some fancy formations, he wouldn't understand at all, but when it came to whether deploying formations could be effective in battle, he had his own set of theories and practical experiences, and was quite formidable in actual combat.
A simplest example is the formation one-one-one, a spread of left, center, and right armies, with the flanks and rear marked by a ! mark, representing the battlefield's most maneuverable cavalry units.
In the era of cold weapons, formations weren't the decisive factor; it was the soldiers' combat quality, morale, will, and command capacity that made the difference.
