The Doctrine of Proportional Response: Star Trek “Balance of Terror”

balance of terror

In Star Trek “Balance of Terror” a Romulan ship destroys four Earth outposts that border the Neutral Zone, a demilitarized region of space. The Captain of the Enterprise, James T. Kirk (William Shatner), must decide what to do after this “unprovoked attack.” Kirk’s response to the Romulan attack is based on the doctrine of proportionality: “a state is legally allowed to unilaterally defend itself and right a wrong provided the response is proportional to the injury suffered.”1

Following the Romulan attack, Doctor McCoy (DeForest Kelley) is the voice of pacifism. He is against a military response, suggesting that it will violate the peace treaty and lead to war. Starfleet personnel were killed by the Romulans, and he does not want any more innocent people to die. However, a non-response, rather than maintaining peace between Earth and the Romulans, would only increase the likelihood of war. By refusing to use military force against an aggressive enemy, a lasting peace is rarely achieved. Having paid no price for their act of aggression, the bully is emboldened to attack again.

In contrast to McCoy’s pacifism, Mr. Spock (Leonard Nimoy) and Mr. Stiles (Paul Comi) both advocate a military response. Stiles tells Kirk, “We have to attack. If we don’t … they’ll report we saw their weapons and ran.” If the Enterprise does not respond, the Romulans will send more ships and attack more Federation outposts. Spock says, “Weakness is something we dare not show.” After considering the viewpoints of Spock and McCoy, Kirk attacks the Romulan Bird of Prey and destroys it. The Romulans pay a high price for their act of aggression—the loss of their flagship—which will dissuade them from attacking again. Kirk’s proportional response restores the balance of power between Earth and the Romulans and ends the conflict.

A proportional response to an unprovoked attack is not an act of revenge—it is a deterrent against future attacks. “Balance of Terror” reminds us that attacking one’s enemies has a cost. In the battle between the Enterprise and the Romulans, Robert Tomlinson (Stephen Mines) is killed. Kirk comforts the grieving widow by telling her, “There was a reason.” Tomlinson died in the line of duty for a noble reason: to prevent future attacks by the Romulans. This is the goal of any just military action: to save the lives of innocent civilians, not only in the present, but also in the future.


  1. “Doctrine of Proportionality,” Council on Foreign Relations, accessed May 31, 2014,

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