Star Trek: 10 Things You Didn't Know About Romulans

At an unknown point after Ambassador Spock's disappearance/death and before the Burn of the 31st century, hopes for the reunification of the Vulcan and (what remained of the) Romulan peoples had become a reality on and in Ni'Var (formerly the planet Vulcan, meaning 'two form'). Some three decades before Star Trek: Discovery made it a magic three, Unification, I & II were being devised as a way to mark the 25th anniversary of the franchise in 1991.

In order to link Star Trek VI: The Undiscovered Country, to be released the same year, with Star Trek: The Next Generation as part of the celebrations, it was decided that nods to TNG would be made in the film and that Spock would hop across to appear in the series. Producers just needed an idea for the Next Gen episodes. As Rick Berman discussed in Captains' Logs: The Unauthorized Complete Trek Voyages, Vulcan-Romulan reunification wasn't the first idea they came up with, in fact, "[We] spent a lot of time kicking things around and finally we came back to Leonard with an idea he didn't particularly like" before finding the "fix."

Eventually, Star Trek VI became the story of the collapse of the Soviet Union and the end of the Cold War, whereas Unification, I & II was the allegory for the reunification of Germany. However, as writer Michael Piller also stated in Captains' Logs, "We [were] really telling the story of the unification of The Original Series and Next Generation, symbolically closing the gap that had always been in the fans' minds, if no one else's, between the two shows."