There are many reasons why I love Star Trek: Deep Space Nine and why it remains my favorite of the Star Trek franchise.
Reason #31: Section 31
One concerted effort Rick Berman and Michael Piller had in mind in creating Star Trek: Deep Space Nine was to give fans a little dirtier version of Starfleet than we’d seen in Star Trek: The Next Generation. Yes, Starfleet is still the future to aspire to, but it’s still made up of human beings who, no matter how evolved they are, are still human.
Over the years on DS9 and STNG we’d seen covert intelligence for both the Romulans (Tal’Shiar) and Cardassians (Obsidian Order), but, as Odo remarks, the Federation would be fools not to have their own such group. Enter Section 31.
The clandestine group is first introduced in “Inquisition” as Dr. Bashir (Alexander Siddig) is rigorously tested by through a holodeck simulation to discover if he has the stuff to work for the organization. Although the next time we see Sloan (William Sadler) Section 31’s objectives are much darker (using Odo to poison the Great Link), the agency sees their actions as necessary to product the Federation from its enemies.
A Star Trek universe where Section 31 can exist is far more interesting, and far more dangerous, than one where it can’t. You need a few dark corners for show like Deep Space Nine, especially one that takes place on one of the furthest outposts in deep space.