The Prussian Kriegspiel: Hidden movement battle games with map and umpire

Kriegspiel is a military simulation played out with wooden blocks on a map. Its most marked difference from other forms of wargaming is that the players cannot see what the enemy is doing. This is achieved through non-player umpires acting within the framework of a ruleset but who have considerable discretion to decide the "inherent military probability" in a given situation. The result is an experience uncannily like that of a real life officer in the time of the horse and the musket.