There is a lot to love about Deep Space Nine before it quote unquote “Gets Good.” The show’s first two seasons are, in a lot of ways, about the things many praise DS9‘s back half for dealing with: the cost of compromising Star Trek’s utopian future on the furthest fringes of its final frontier. But even then, few things prepared its audience for the moment everything changed with the arrival of the Dominion War.

While the opening volleys of that conflict are some of its most famous, for good reason, the actual turning point that sees DS9 begin to pivot to a war footing happened 30 years ago today with the broadcast of the season two finale, “The Jem’Hadar,” and the start of a Cold War that would soon turn hot, and present Star Trek the most radical challenge to its ideals thus far. For the most part, it’s a Trek episode like many before it. Thinking he was getting a quiet vacation to the Gamma Quadrant with his son Jake, Commander Sisko finds himself dealing with the complicated annoyance of Jake’s best friend Nog tagging along, and then Nog’s uncle Quark, hoping to get the Commander’s ear, joining uninvited, only for them all suddenly to find themselves prisoners of a strange, hostile new race they’ve never encountered before the first night they make camp.

Little in the way of resources—Deep Space Nine didn’t have a ship at this point, so our heroes just have their runabout shuttle, and what camping gear they bought with them—and facing an unknown enemy with all the power, this is the kind of episode we’ve seen many times before in Star Trek, as Sisko, Quark, and a potential new ally in a psychic alien woman named Eris who was likewise caught fleeing the titular Jem’Hadar, try and fail to either escape the clutches of their new foes or even connect and understand them diplomatically. It’s perhaps otherwise the kind of episode that ends with our heroes getting rescued, or breaking out, and proving that Starfleet’s finest and their allies, even caught unawares and without their usual resources, can work together, save the day, and make it out of harm’s way. They’re Star Trek heroes! That is what they do. But “The Jem’Hadar” is not a typical Star Trek episode in what was already not a typical Star Trek show, and while we get that in part, it’s the climactic twist that makes Deep Space Nine’s boldest gambit crystal clear.

In the climax of the episode, after Sisko has failed to check in with the station, Kira and Odo work with the Federation to send the USS Odyssey, and another runabout to the Gamma Quadrant in search of the Commander. They meet up, Jake and Nog rescue Quark, Sisko, and Eris, and a fight breaks out between the Jem’Hadar and the Odyssey. A fight the Odyssey very quickly starts losing. This too is perhaps expected sometimes—Star Trek has plenty of firefights break out where our heroes can seemingly not land a shot, but their foes can find ways to lance through their shields, usually before some clever techno babble and problem-solving finds a way to turn the odds in Starfleet’s favor. That doesn’t happen here, and then the other shoe drops: as the Odyssey and the runabouts begin to retreat back to DS9, the Jem’Hadar ship—unharmed by what little the Odyssey could throw at it despite it being the overwhelmingly larger ship—performs a kamikaze charge directly at the cruiser, blowing itself and the Odyssey up instantly. In stunned silence, the remaining shuttles are left to hobble back home.

With one final twist—that Eris was in fact working with the Jem’Hadar, and is a representative of their shared masters in the Dominion, who do not want the Federation encroaching on their territory; she teleports away to parts unknown before she can be detained—the season ends in this uneasy space. This one fight is over, and was arguably over before it even began, but the Dominion will inevitably return… and Starfleet is clearly not ready for what it is capable of.

It is the moment everything changes on Deep Space Nine. The show had dire threats before this—the station had been boarded and occupied in a hostile coup d’etat, Sisko had already dealt with the emergence of a new guerrilla front in the Maquis, opening up old wounds with the Cardassians. But there is a weight in seeing a ship like the Odyssey not just unable to touch the Jem’Hadar, but be taken out like nothing, just to send a message that the Federation has no idea what it’s dealing with. It’s an especially potent message, because the Odyssey is not just any Federation ship, it’s a Galaxy-class cruiser, at that point the idealized apex of Starfleet shipcraft, the vision of its scientific expansionary aims. It’s not just the best of Starfleet, it’s the best of Star Trek: the Galaxy-class was the Enterprise. It was The Next Generation. And here was its successor show, having already danced with the complicated legacy of its predecessor, blowing that symbol up: what the Federation is, what Star Trek was before this, is not prepared for what is to come.

The impact was made clear when Deep Space Nine returned. We’re immediately introduced to the Defiant in “The Search,” the first Starfleet vessel we’ve seen on-screen explicitly designed for combat, a two-part premiere that shows even with Starfleet baring its teeth like this, Deep Space Nine’s heroes are still not ready for what the Dominion represents. The next few seasons of the show represent a slow and certain splintering of the Alpha Quadrant powers as we’d come to know them over TNG and the opening seasons of DS9, as the Dominion’s agents sowed paranoia and distrust—the seeming destruction of the Cardassian and Romulan intelligence agencies, a return to hostility between the Federation and the Klingon Empire, brewing military coups at the heart of Starfleet itself.

By the time the Dominion War turns hot at the climax of season five, Deep Space Nine has all but completed its transition into the show it is now always lauded for being. But even as it went on to those great heights, there are still few more potent images in the entire series than the Odyssey wreathed in flames as its hull splinters into pieces—a warning, and a promise that Star Trek would never be the same.

Want more io9 news? Check out when to expect the latest Marvel, Star Wars, and Star Trek releases, what’s next for the DC Universe on film and TV, and everything you need to know about the future of Doctor Who.