This video shows why fire by rank sucks for the AI. The AI pauses and has horrible response as it gets all shot up while reloading. Volley Fire AI lays down a continuous line of fire and will bring big hurt to your army. I do not know what battle difficulty the user used for this battle but my guess is was NOT hard or very hard as the enemy troops routed too easy. If it was on Very Hard his army would have been in big trouble. So Volley Fire mod version One and Very Hard battle settings that is key.