WARNING: The following contains spoilers for Star Trek: Discovery Season 3, Episode 2, "Far From Home," now streaming on CBS All Access.
In Star Trek: Discovery's Season 3 premiere, Michael Burnham is jettisoned 930 years into the future, to 3188 , the furthest point canonically in the franchise timeline. In the 32nd century, the United Federation of Planets is no more, and time-travel technology is outlawed in the aftermath of "the Temporal Wars." Devoted fans will, no doubt, recognize the allusion to the events of a sprawling story arc from the prequel series Star Trek: Enterprise.
By the 28th century, an interstellar treaty known as the Temporal Accord prohibited the use of time travel to alter the course of history. However, certain time-traveling factions opposed this decision and sought to use the technology for their own benefit. Attempting to gain a foothold over the times stream, they sent out temporal agents to protect the timeline.
The Temporal Cold War was a conflict fought between several time-traveling factions and their proxies, each representing a different point in time. The four main factions were the Suliban Cabal, the Na'kuhl, the transdimensional Sphere-Builders and a 31st-century version of the Federation. They employed proxies and instigated major events to undermine the 22nd century, the setting of Enterprise, in an effort to further their own goals
In the Enterprise premiere, "Broken Bow," Captain Archer and his crew encounter augmented Sulibans during their mission to return an injured Klingon to his home planet. Working for a mysterious benefactor from the 28th century, who was unable to travel through time, the aliens carried out clandestine attacks upon the Klingon Empire in hopes of sparking a civil war. The identity of the mysterious figure was never revealed in the series, but co-creator Brannon Braga confirmed him to be a future version of Jonathan Archer.
The story arc continued in Season 1, Episode 11, "Cold Front," in which Enterprise crewman Daniels was revealed to be a temporal agent from the 31st century. He was seemingly killed while trying to capture a Suliban named Silk, but he later reappeared to save the Enterprise crew after they were accused of destroying a mining colony. Daniels later aided Archer in making peace with the Xindi, an alien species that was being manipulated by the Sphere-Builders to attack Earth in order to prevent the Federation from ever existing.
The Temporal Cold War ignited into an all-out conflict when a rogue time-traveling faction, the Na'kuhl, returned to the 29th century after making significant changes to Earth's history. The other factions tried to annihilate each other, further escalating the conflict. The Temporal War started as a result of a predestination paradox in which a nearly defeated Na'kuhl escaped to an altered version of 1944 Earth. After returning to their own time, they sparked the very conflict that nearly caused their defeat in the first place. After being transported to 1944, Archer and his team stopped the paradox by killing Vosk before he could return to the 29th century, thus resetting the timeline and ending the Temporal War.
Presumably, after the conclusion of the Temporal War, time-travel technology was outlawed and destroyed in order to avoid another conflict of that scale. However, that peace didn't last for long, as later in the 31st century an event known as the Burn caused dilithium crystals in the galaxy to spontaneously explode, leaving the Federation in near-collapse. Judging from the timeline, the Burn might be linked to the Temporal War. Someone -- either a rogue faction from the war or a future version of Burnham -- caused the incident to occur when they attempted unsanctioned time travel.
Whatever caused the incident to occur, the Temporal War has left a huge impact on the galaxy going forward into the 32nd century. With time travel seemingly eliminated, the Discovery team will have to think out of the box if they ever hope to return to their own time period.
Streaming on CBS All Access, Star Trek: Discovery stars Sonequa Martin-Green as Commander Michael Burnham, Doug Jones as Commander Saru, Anthony Rapp as Lt. Commander Paul Stamets, Mary Wiseman as Ensign Sylvia Tilly, Wilson Cruz as Dr. Hugh Culber, David Ajala as Cleveland "Book" Booker, Blu del Barrio as Adira, Ian Alexander as Grey, Tig Notaro as Chief Engineer Reno, Ethan Peck as Spock and Michelle Yeoh as Philippa Georgiou. New episodes of Season 3 air on Thursdays.