The second occurred about 50 years later, in the year 2344, when a Klingon outpost on Narendra III was attacked by Romulans. The first was the destruction of their moon Praxis in the opening to Star Trek VI, which devastated the Klingon homeworld and forced them to approach the Federation for peace. Within the Star Trek universe, three key events established the basis for the Klingon-Federation alliance. RELATED: Star Trek: One Of The Original Series' Best Episodes Almost Had A Different Ending

Voyager added a second Klingon principal with B’Elanna Torres, and, barring any revelation from Star Trek: Discovery or Picard, the alliance appears to still be going strong. Despite some difficulties between the two powers in Deep Space Nine, they emerged from the Dominion War as firm partners. Star Trek VI: The Undiscovered Country, the last official outing of the original crew, set the narrative groundwork for peace between them. That allowed the show to explore the Klingon culture at length, a process made easier by the ability to insert regular cast members into the proceedings as allies. Roddenberry wanted to push the utopian aspects of the Federation, in which the Klingons had not only become allies, but one of their own - Worf - served on the bridge of the Enterprise. Then, things changed quite suddenly with the start of The Next Generation. That continued into the movies, most notably in Star Trek III: The Search for Spock, where Christopher Lloyd’s Commander Kruge murdered Kirk’s son. The Organians stopped a burgeoning war between them, but the Klingons returned in six additional original series episodes. Kirk described ways they transformed entire planets into slave labor camps, and their commander Kor threatened the Organians with death for the slightest failure to obey commands.

They first appeared in Star Trek, Season 1, Episode 27, “Errand of Mercy,” which opened with their surprise attack on the Enterprise without warning. The in-universe change was dictated by the creative directions Gene Roddenberry and others took the franchise.

How long did the klingon war last