mmmm...do you have promotion-saving turned on? If so, are the AI using the extra 10XP from the Tactical School to give themselves a free auto-heal as a 1st promotion, do you think ? Or perhaps my understanding is incorrect and the AI can alway "promotion-save" regardless of whether the option is turned on in Advanced Game Set-up. Because the Tactical School's promotion is only an extra 10% to combat strength, and if your musketmen started life in a city with the Tactical School they should also have the extra 10% strength. The promotion for the Tactical School applies to both Melee and Gunpowder units, whereas the one for the Warrior School (the version of the building you can construct from the start of the game) only applies to Melee units.