Question: Name the American actor, best known for his role as Captain B.J. Hunnicutt in a television series which included a 2-episode story arc where we see the departure of Captain Trapper and his replacement by this new Captain? 
Sentence (from "Welcome to Korea"): "Welcome to Korea" was a 2-episode story arc, the 73rd and 74th episodes of the "M*A*S*H" television series, and first two episodes of the fourth season of the series.
Relevant evidence: Yes