World War One Series:
Each game is an Operational Level simulation of the campaigns of World War One. The game is played by two players; one controls the Central Powers forces (Germany, Austria-Hungary, and their allies), the other controls the forces of the Entente (France, Great Britain, Russia, and their allies). All of the units depicted in these games were available to the historical commanders. Each of the units has combat and movement capabilities that represent what the historical unit was capable of doing. It is up to the players to conduct operations with their units within the framework of these rules. Other games of the series can be tied together with these games to create more comprehensive simulations. The instructions for doing so are found in the scenario specific rules.
Vassal Modules allow owners of the games to play via computer.
Read more about this on Der Weltkrieg's Vassal page.