The Kohm are one of two ethnic groups on the planet Omega IV who, an unknown amount of time ago (at least 1,000 years), fought a terrible bacteriological war against the Yangs. The name "Kohm" is a corruption of the Earth's 20th century word "communist", an example of Hodgkin's Law of Parallel Planetary Development at work.
Physiology and appearance
Kohms are Asiatic in appearance, and dress in a manner similar to Mongol tribesmen of Earth. As a result of the biological warfare waged in their past they have extremely powerful immune systems. A benefit of this is that Kohms have extremely long life-spans (the father of a Kohm named Wu was over 1,000 years old and still alive), and suffer from no known form of disease.
The biological warfare waged on Omega-IV in the distant past nearly destroyed the Communist civilization, and all but did the same to that of the Yangs. The survivors of the two sides engaged in a millennium long struggle for dominance on the planet. Over that period, Kohm villages were destroyed by the Yangs, until only one such village remained. The Yangs began to mass for a final attack.
The violation of the Prime Directive by Starfleet Captain Ronald Tracey of the starship USS Exeter, who used his phaser to assist the Kohms in battle, stove off defeat temporarily. However, the intervention of Captain James T. Kirk of the USS Enterprise resulted in the eventual sacking of the last Kohm village.
Yang Chief Cloud William promised Kirk that the words of the Yang "Holy of Holies" (the United States Constitution) would be applied to the Kohms as well as the Yangs. This would seem to indicate that at least some Kohms in fact, survived. (TOS: "The Omega Glory")