In case you skip it...

This episode features an important concept that will come back many times - the Prime Directive.

The Prime Directive is one of Starfleet’s most important rules, based on a philosophy of noninterference with other cultures.

For cultures on the galactic stage (such as the Klingon Empire or the Ferengi Alliance) this mostly just means not interfering with their internal affairs.

For cultures that have not yet developed warp capability and entered the galactic stage (so-called “pre-warp” societies) it is much stricter. Even simply revealing that other races exist is considered a violation, as it would have a sizable impact on their cultural development. Consequently, pre-warp societies tend to just be observed remotely - if interaction is needed, Starfleet will disguise themselves as natives of the society and minimize their interaction as much as possible.

The reason for the Prime Directive is that in the Federation’s history, it’s been repeatedly demonstrated that even well-intentioned interference in other cultures (such as providing advanced technology to cure disease or prevent disasters) backfires hard and has catastrophic effects on the culture’s development.

That said, it’s recognized that it is sometimes acceptable to violate the Prime Directive - particularly in order to (a) minimize the damage caused by a previous violation or (b) to prevent the total extinction of the other culture. All violations are investigated and reviewed, and those that are found to be unjustified are punished by arrest and court martial.

Despite how well-established this flexibility is, some writers have a frustrating tendency to forget about it and create stories in which Starfleet is caught in a moral dilemma because the Prime Directive forbids them from preventing the annihilation of a pre-warp society (generally due to a planetary catastrophe on their homeworld). This is dramatic, but runs counter to the intent of the Prime Directive. In situations like these, Starfleet would be well within its rules to prevent the society’s destruction - though ideally they would do so in secret without ever being discovered.