The Impulse system is a game system used by several games published by Avalon Hill Game Company. Games using this system include Storm over Arnhem, Thunder at Cassino, Turning Point: Stalingrad and Breakout: Normandy. The complexity of the games can be generally classified as "Intermediate" although the latter games are somewhat more complex.
This page attempts to give the reader an general idea of how the Impulse System works. Because it is used in different games, the system may vary from game to game.
The mapboards in these games are generally divided into irregularly shaped areas. Each area has an ID for record purposes, as well as a Terrain Effect Modifier(TEM), which aids the defender in combat. Offboard zones are attached to the side of the board to allevate the "edge of the world" problem.
Units represent formations that took part in the particular campaign. This ranges from squads/platoons in Storm over Arnhem to regiments in Breakout: Normandy.
Each unit has a Fresh side and a Spent side, to reflect the status of the unit. Most unit functions can only be performed by Fresh units, while spent units can do little more than defend itself and maybe move.
Fresh units become Spent by performing any activity, such as movement and combat. They can also become Spent by absorbing losses during combat. To recover Fresh status depends on the game. It is automatic in Storm over Arnhem and Thunder at Cassino. In Turning Point Stalingrad Spent units are returned to fresh status after a variable number of turns. Supply points must be consumed by a spent unit in Breakout Normandy to return to Fresh status.
Each turn is made up of impulses. During each impulse, players may activate units in one area. Active units in an activated area may move and engage in other activities such as (depending on unit type) assaults, bombardments, etc.
Combat is resolved by competetive die rolls modified by the strength of one attacking/defending unit, additional units, terrain. The difference is the number casualties that the losing side must absorb, by retreat, converting units to spent or outright elimination.