Watch on the Rhine: The Siegfried Line Campaign, 1944-45 (WotR) is a two-player (solitaire adaptable) historical simulation of the final operations of World War II in northwest Europe.

Each hexagon on the map represents 10 miles (16.2 km) from side to opposite side. The units of maneuver are almost all divisions or brigades or their ad hoc equivalents. There are two corps-sized units representing the First Allied Airborne Army when it’s used in paradrop operations. Each full game turn represents 10 days to one month of ‘real time,’ depending on the time of year.

The maps illustrate the militarily significant terrain found in and around this border area of western Germany in 1944-45 when portrayed at this scale. The national boundaries shown are the final internationally ones from just before the war began in 1939.

A hexagonal (“hex”) grid is printed over the map to regulate the placement and movement of units across it, much like the squares in Chess and Checkers. A unit is considered to be in only one hex at any one time. Every hex on the map has a unique four-digit identification number printed within it. They’re provided to help find exact locations more quickly and to allow for the recording of unit positions if a game has to be taken down before it can be completed.