Why did the Federation and the Cardassians swap planets?
A Thirty Years Too Late Rant
In the lead-up to the launch of Star Trek: Voyager, the other two shows at the time (The Next Generation and Deep Space Nine) tried to seed out plotpoints that would then be built upon in the new series. Primary among these was the Maquis, an organization of former Starfleet officers and other Federation citizens who formed a guerrilla/terrorist organization in the Demilitarized Zone between the Federation and the Cardassian Union. As it is explained to us, both the Federation and the Cardassians had settled planets throughout the territory that later became the DMZ, and after years of border conflicts and armed encounters the two powers signed a peace treaty that formed the DMZ as a buffer and delineated which planets fell under each jurisdiction. Some planets that had been settled by the Federation were transferred to Cardassian rule, and some Cardassian planets wound up administered by the Federation. The goal of the Maquis was independence for their colonies in the DMZ, which they chose not to leave after the government handover.
Though this plotline was actually barely utilized in Voyager (And at times was completely forgotten about), it was picked up by TNG and DS9 for stories here-and-there and even for a few standout episodes. However, one thing which was never explained, and never really even touched on, was why the Federation and the Cardassians swapped planets. It wasn’t as though one power “won” the treaty and gained territory at the expense of the other, it is very clear that each exchanged an approximately equal amount of territory so the net loss/gain was zero. They just wound up with some planets inhabited by citizens of a foreign power instead of their own people. It would have made so much more sense for them each to retain control over their own colonies, and then divvy up the rest of the DMZ as needed.
Now, I can think up many hypotheticals to explain this, and in real-life there are many examples throughout history of two countries signing what seem to be bizarre treaties because they each have unique needs. One nation might be largely landlocked and they desperately need a port city, so they are willing to give up a large portion of land elsewhere if it gets the other country to not object to losing a port. Or maybe some piece of land has religious or cultural significance to one side, so they want it even though there is no material benefit. Or maybe it’s due to an outside factor, like a third polity in the region that doesn’t want to share a border so the maps are redrawn to keep them from technically touching. Any of these could have sufficed (With suitable Star Trek-isms to adapt the concepts to space) but they weren’t used. The Federation and the Cardassians apparently just both agreed to swap planets for no discernible reason.
And this bothers me. I know it’s a common joke that “A successful compromise means nobody is happy”, but what did this treaty actually accomplish for either side? What self-serving, machiavellian rationale did the ever-duplicitous Cardassians have for ceding jurisdiction over their own people? Why did the Federation want to take responsibility for governing dozens of Cardassian planets that had no interest in joining the Federation?
TNG and DS9 were both capable of generating compelling, subtle, and complex diplomatic plotlines, and here they just...didn’t.