Star Trek: The Original Series
#1 Balance of Terror
“The Neutral Zone: Established by treaty after the Earth-Romulan conflict of over a century ago. As you may recall from your histories, this conflict was fought by our standards today with primitive atomic weapons and in primitive space vessels which allowed no quarter, no captives; nor was there even ship-to-ship visual communication. Therefore no human, Romulan, or ally has ever seen the other.