Operational Combat System
The Gamer's / MMPs popular series of wargames simulates 20th century battles at levels ranging from battalions to divisions.
"Operational Combat Series (OCS) games simulate campaign-level combat from 1900 to the mid-1950s. The series goal is to allow a sophisticated study of historical events while maintaining mechanical simplicity. Every facet of modern combat is modeled."
(from MMP webpage)