Dunnigan's FRANCO-PRUSSIAN WAR introduced this evolving operational wargame system. Young simplified it in THE WILDERNESS CAMPAIGN and LEE MOVES NORTH. In additional to similar scale they are all fairly simple wargames that feature maneuvers, leaders, supply, and railroads in the age of rifles. But they are all slightly different from each other, with different CRTs (in fact, the FPW has six based on defender strength) that reflect their campaigns. They all use a step loss system; FPW and WC by single points, LMN by larger steps. They all use dummy units. FPW uses fortresses. WC features entrenching and fortified city zones. FPW has railroad repair units but no cavalry (explained that doctrine failed a useful cavalry role at that time). The other two American Civil War games include cavalry units.