Der Weltkrieg WWI wargame series is designed by David Schroeder and published by SPW/Decision games.
The series has a unique hex-system where the terrain is determined by the hex side instead of the hex. Its an operational level game with most units being divisions. The combat system is also different from most hex and counter games. Each side counts up there total strength and fires. There is no rounding off and no odds table. Every strength point counts. Casualties are taken from the best units first and if you want to advance after combat the units that took the casualties must be the first ones to advance. All combat is dependent on supply points (SPs). If you don't have many supply points you aren't going to get very far.
The games play is pretty straight forward and not complex at all.