“You’re condemning this whole planet to a war that may never end,” Dr. Leonard McCoy chastised Captain James T. Kirk, in the 1968 Star Trek episode “A Private Little War.” “It could go on for year after year, massacre after massacre.” Broadcast twice in the science-fiction series’ second season, “A Private Little War” is one of Star Trek’s four explicit allegories on the Cold War logic driving American involvement in the Vietnam War.