The Enterprise crew are the first Star Fleet representatives to arrive on the planet Organia as hostilities break-out between the Federation and the Klingon Empire. Organia offers tactical advantages and is inhabited by a passive, non-progressive, agricultural, humanoid people.
John Colicos turns in a landmark performance as a Klingon colonial administrator who arrives a few minutes after Kirk and Spock, with a full military contingent (uninhibited by the Federation's Prime Directive). Colicos' Kor becomes the archetypal personality for Klingon military leaders until the Klingons are somewhat redefined in DS9. Kor establishes mercilessness as his model and begins executing Organians who do not offer complete and open cooperation. And the Organians don't care. They sit back, aloof - neither resisting nor cooperating, and frustrate both Kor and Kirk.
The episode offers a brilliant, somewhat nihilistic and humbling resolution - which you will have to see for yourself, and is one of the most satisfying of TOS. It's only negative point is the over-abundant and unnecessary 'witty banter' between Kirk and Spock as they plot against the Klingons - more subtly exploited in later Coon scripts.
Highly recommended.