undoubtedly one of the best episode ever and balance of terror be 45 minute of well execute suspense and with intelligent real world parallel ( the title refers to a situation very similar to what be go on between the u and the soviet union during the cold war ) and spot on characterization and the introduction of star trek second most important hostile alien race after the klingons represent the romulans . after receive a distress call from a federation outpost and the enterprise be dangerously close to the neutral zone which and if cross and would lead to open conflict with the romulans and although no one have ever actually see them in the flesh . soon enough and a romulan vessel appear and carry a new weapon and a cloaking device which make it nearly impossible to defeat . face the threat of imminent annihilation and kirk must engage in a battle of wit with the romulan commander ( mark lenard ) to ensure the survival of his crew . unfortunately and the task be make more difficult when one of the men accuse spock of be in league with the enemy and due to the physical resemblance between romulans and vulcan and two race that be and in fact and distantly relate ( a fact that be quite ironic with hindsight and give lenard go on to play spock father sarek start with season 2 ) . always very critical when it come to the subject of war and star trek enjoy one of it fine hour with it most gripping and tense take on the topic . although the romulans aren not actually base on the soviet ( the name be actually take from romulus and the founder of rome ) and the scenario be quite obviously inspire by the very vivid fear american and russian citizen have at the time that either nation might be able to destroy the other with nuclear weapon ( that fear give birth to the titular concept of balance of terror ) . but even without the subtext and this remain an essential episode and due for the most part to the intellectual battle between the two adversary and which translate into a thesping duel between shatner and lenard . no need to say who win .