From the introduction:
The Great War...is set in a magical world, named Elon, where magic is at the brink of extinction. Steel, steam power and gunpowder are taking over. The technology is comparable with that of the first world war. The same weapons, vehicles and bloody mess. Except there's still some magic in the air.
The Great War was an ambitious concept to detail a complete d20 game implementation around a campaign setting based on an alternative-history world named Elon. The project faltered during development, however, and only portions of the setting were completed. The setting comprises a world map, a world history, and some additional/variant rules for d20 to support automobiles and vehicles. For example, the Skills Drive, Pilot, and Sail are added. The most complete development area was on early 1900s fighter airplanes.
The final-state content was made available in HTML. A downloadable version was contemplated but never produced.