Missippi Fortress ia a two player strategic simulation of the Union campaign of 1863 that culminated in the capture of Vicksburg and the splitting of the Confederacy. Players assume the roles of Grant and Pemberton. The compact Union forces are powerful, but initially weaker than that total rebel strength, and forced to take the offensive. The two Confederate armies are widely separated at first, but can form a decisive mass if they can link up.

The map depicts the theater of operations in the central Mississippi valley. It is divided into areas, stretching from Bruinsburg to Jackson. Each map area serves to regulate movement and combat and approximates a 14 mile square of terrain. The two campaign game scenarios cover the period between April 29th & July 4th using two day turns. a smaller scenario that can be played in an evening covers the key maneuvering and combat that took place around Champion Hill.

The game hinges around maneuvering your combat units to seek a decisive tactical combat advantage and denying the enemy the opportunity to successfully attack you. The tactical display, used for resolving combat action, illustrates the difficulties of Civil War combat. Realistically, units remain inverted on the map until combat occurs. One cannot be sure an enemy build-up on one's flank is a serious menace, or a ruse to force abandonment of a powerful defensive position.