Star Trek: Season 1, Episode 18. "Arena"

 Summary:

As the officers visit Commodore Travers on Cestus III, Travers request tactical people as he has an interesting problem. When they beam down they find the colony outpost destroyed. After they find life a mile away, they are immediately under attack.

Analysis with spoilers:

Kirk believes the messages he'd received from the Commodore were faked. Red shirt dies. Meanwhile, Enterprise is under attack. If they lower shields to beam up officers, they would be vulnerable to attack, so Kirk orders shields up and retreats.

Kirk dashes and tumbles to an artillery depot. When Sulu's attacks against alien vessel are ineffectual, Kirk advises them warp away. Spock believes, when the aliens are moving, he must join Kirk. They fire a type of grenade that causes aliens to beam away and flee. Kirk decides to search for survivors. Enterprise returns.

Survivor explains ruthlessness of the aliens in battle even though the colonists tried to surrender. He also states that they never sent the Enterprise any messages. Kirk concludes that the Enterprise was lured to be destroyed in order invade their space. The Enterprise pursues.

Spock and Kirk debate over the need for retaliation. Kirk is decided that they must be destroyed. They pass a system that stops them both. The Metrons have stopped both. Federation ship captain must fight the Gorn ship captain. The losing captain's ship will also be destroyed.

The scenario matches the common saying where kings, presidents, and tyrants should fight the wars.

The battle here differs from Brown's. There is no barrier. The Gorn is a lizard (as opposed to a tendriled roller) and stronger if slower than Kirk. Kirk believes he is smarter, but the Gorn listens in as Kirk records his plans. Kirk hunts for weapons while the Gorn builds them. Kirk drops a boulder and thinks he has the Gorn, but it rises. Kirk flees into a trap. Kirk escapes but is exhausted.

The Metrons tell the Enterprise that Kirk is done for and to prepare to die. Nonetheless, Kirk dashes down hill. Meanwhile, the Enterprise watches on screen and suddenly, they understand the Gorn might have been defending their own space against the human invaders.

Meanwhile, Kirk invents gunpowder as the Gorn approaches. Kirk succeeds but decides against killing the Gorn. The Metrons free both parties without killing. Enterprise zapped back toward home.

Quotes:

1. Spock: "Doctor, you are sensualist."
   McCoy: "You bet your pointed ears I am."
2. McCoy: "We appeal to you in the name of civilization. Put a stop to this."
   Metron: "Your violent intent and actions demonstrate you are not civilized."
3. Kirk: "We're a most promising species as predators go."

Notes:

1. Red shirt zapped.
2. Not only is this episode based on Fredric Brown's "Arena", it also alludes to Murray Leinster's "First Contact" as a kind of framing device with slightly different outcomes (Enterprise instantly transported back into familiar space as opposed to swapping ships.
3. Sustained Warp speed 7 is dangerous.