Open Field Battle is a simple wargame portraying generic 17th-century combat; no specific battle is represented. Each player has a force of pikemen, cavalry, musketeers, and cannons. Each turn a player gets a random number of command points to spend on musketeers and cannons firing and on pikemen and cavalry moving and assaulting. Combat is deterministic; the result depends on the formation the defender is in and the status of the defender and any neighboring units. E.g., a lone defender or one at the end of a line is disrupted (or eliminated if already disrupted), but one with two undisrupted neighbors merely retreats. The neighboring units may suffer effects as well. Optional rules allow for different ways of using the command points and the possibility of saving them from turn to turn.