From the introduction:

Cobra - Game of the Normandy Breakout , is a regimental/divisional scale simulation of the allied break-out from the Normandy peninsula in the summer of 1944, which culminated in the encirclement of some 160,000 German troops in the "Falaise Pocket." Each game-turn is equivalent to three days of real time, and each hex represents a distance (across) of 3.2 kilometers.