The character of COL Potter was played to a "T" by Morgan. Initially appearing to be a classic "regular Army" officer and surgeon, Potter's sometimes gruff and grizzled exterior belied a man exposed to two World Wars and the killing of young men. This played into the shows generally anti-war theme. His character was the "straight man" of sorts on the show playing against the antics of the rest of the cast, but occasionally even the old Colonel had his moments. Here is the best clip I could find of Harry Morgan as COL Potter and he displays some fine acting chops here.
As a young boy growing up in the 70's, MASH was really the only introduction to the Army I had other than the occasional war movie on the weekends. In an era post-Vietnam, the military was generally not portrayed in favorable ways. Despite its true anti-war/anti-military themes, I enjoyed the show as a kid and it did influence my decision to enlist when I turned 18.