system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek]What was the most important decision made or action undertaken by any member of Starfleet during any of the TV shows or movies?

The final episode of TNG is excluded as that one would win hands down and then the question would not be very interesting. So anything related to that from previous episodes is also discarded.  Everything else is fair game.


And if not the most important, what are some of very important ones? Ones that stand out.
gpt
Tasha Yar deciding to go back with the yesterday Enterprise, thereby giving them the tactical expertise they needed to last long enough in the battle to be detected by the Klingons, who then learn that humanity has a sense of honor and thereby plant the seeds for the alliance between the feds and the empire.

Either that, or Sisko tricking the Romulans into entering the Dominion War.