Star Trek: Enterprise (originally titled simply Enterprise until the start of the third season) is a science fiction television series. It follows the adventures of humanity's first warp 5 starship, the Enterprise, ten years before the United Federation of Planets shown in previous Star Trek series was formed.
Enterprise premiered on September 26, 2001. The pilot episode, "Broken Bow", takes place in the year 2151, halfway between the 21st-century events shown in the movie Star Trek: First Contact and the original Star Trek television series. Low ratings prompted UPN to cancel Star Trek: Enterprise on February 2, 2005, but the network allowed the series to complete its fourth season. The final episode aired on May 13, 2005. After a run of four seasons and 98 episodes, it was the first Star Trek series since the original Star Trek to have been cancelled by its network rather than finished by its producers. It is also the last series in an 18-year run of back-to-back new Star Trek shows beginning with Star Trek: The Next Generation in 1987.
In May 2000, Rick Berman, executive producer of Star Trek: Voyager, revealed that a new series would premiere following the final season of Voyager. Little news was forthcoming for months as Berman and Brannon Braga developed the untitled series, known only as "Series V", until February 2001, when Paramount signed Herman Zimmerman and John Eaves to production design Series V. Within a month, scenic designer Michael Okuda, another long-time Trek veteran, was also signed. Michael Westmore, make-up designer for Trek since Star Trek: The Next Generation (TNG), was announced as working on Series V by the end of April. Returning as director of photography would be Marvin V. Rush, who had been working on various Treks since the third season of TNG. For visual effects, Ronald B. Moore, who had previously worked on TNG and Voyager, was brought in.
However, the biggest news would wait until May 11, 2001. The title of Series V was revealed to be Enterprise, with Scott Bakula, of Quantum Leap fame, playing Captain Jeffery Archer, a name that was quickly changed to Jonathan Archer due to fan feedback. Four days later, the rest of the main cast was announced, though the character names would not be announced until the next day.
The first two seasons of Star Trek: Enterprise depict the exploration of interstellar space by the crew of an Earth ship able to go farther and faster than any humans had previously gone, due to the breaking of the Warp 5 barrier, analogous to the Bell X-1 breaking the sound barrier, that made interstellar travel feasible. The crew faces situations that are familiar to Star Trek fans and shows the origins of some concepts which have become taken for granted in Star Trek canon, such as Lt. Reed's development of force fields and Captain Archer's questions about cultural interference eventually being answered by later series' Prime Directive.
A recurring plot device is the Temporal Cold War, in which a mysterious entity from the 27th century uses the Cabal, a group of genetically upgraded Suliban, to manipulate the timeline and change past events. Sometimes sabotaging Enterprise's mission and sometimes saving the ship from destruction, the entity's motives are unknown. Agent Daniels, a temporal agent from the 31st century, visits Captain Archer occasionally to assist him in fighting the Suliban and undoing damage to the timeline.
In the past ninety years since Star Trek: First Contact, the Vulcans have been mentoring humanity to what they see as an appropriate level of civilization, routinely holding back scientific knowledge in an effort to keep humans stranded close to home, believing them to be too irrational and emotionally-dominated to function properly in an interstellar community. When Enterprise finally sets out, the Vulcans are often conspicuously close by. This generates some friction as, in several early episodes, Archer and others complain bitterly of the Vulcans' unsubtle methods of checking up on them.
 Season 3
The third season sees the change of the series' name to Star Trek: Enterprise as well as an updated main title theme. Season three introduces the Xindi, an enemy bent on annihilating humanity via a planet-destroying super weapon.
The third season follows a single story arc, beginning in the second season finale "The Expanse", in which a mysterious probe cuts a wide, deep trench from central Florida to Venezuela, killing seven million people. Enterprise is recalled and retrofitted as a warship, with more powerful weapons and a group of elite Military Assault Command Operations (MACOs). Enterprise travels through an area known as the Delphic Expanse to find the Xindi homeworld and prevent another attack against Earth. The crew learns in "Azati Prime" that the Sphere-Builders, a transdimensional species, have technology that allows them to examine alternate timelines. The Sphere-Builders know that in the 26th century, the "Federation" fleet, led by Enterprise's distant cousin, the Enterprise-J, will lead an attack against them that will defeat them. They wanted the Xindi, who revered them as "the Guardians," to destroy Earth in the hope that this would deter the formation and existence of the Federation. However, in the season finale, "Zero Hour", Enterprise manages to defeat the Sphere-Builders and destroy the Xindi weapon. They also succeeded in returning the Expanse to normal space. The season ends with the Enterprise being mysteriously transported into the middle of World War II. This plot was resolved in "Storm Front", Parts I & II.
 Season 4
The show was renewed for a fourth season on May 20, 2004. The renewal moved the show from Wednesday night to Friday night, a move that seemed to replicate the third season renewal of the original Star Trek, when it was moved from Thursday night to the Friday night "death slot". Many cast and crew members supported it, saying that The X-Files gained more viewership during its first three years on Friday nights. As a sequel to "Zero Hour," "Storm Front" and "Storm Front, Part II," opened up the fourth season on October 8 and 15, 2004. The episodes ended the ongoing Temporal Cold War arc, which proved very unpopular among the show's viewers during the first three seasons. The Xindi arc, started over a year ago in "The Expanse," ended with the third episode, "Home," which mostly dealt with Captain Archer's ethically and morally questionable actions during the yearlong mission in the Expanse. The general theme of the season was a refocus on the prequel concept of the series, with many episodes making reference to themes, concepts, and characters from past series. The fourth season saw Brent Spiner (Data from Star Trek: The Next Generation) as the imprisoned scientist Dr. Arik Soong, an ancestor of Data's creator (Dr. Noonien Soong, also played by Spiner in at least two episodes of Star Trek: The Next Generation), in a three-episode arc at the end of which Soong abandons the concept of improving mankind in favor of creating artificial intelligence: an allusion to what will eventually become Data.
The Soong episodes later gave rise to a story arc where the Klingons were attempting to improve their species through the continuation of Soong's work. This allowed for an explanation of why the Klingons on The Original Series lacked brow ridges and were much more human looking than Klingons in any of the other series.
Season 4 also addressed some discrepancies between the Vulcans of The Original Series and those depicted in Star Trek: Enterprise. In the Vulcan Civil War arc, Romulan subversion of the Vulcan High Command leads to a splinter group of Vulcans opposed to the High Command's actions, believing those actions to be against the teachings of Surak, the mythic leader who brought logic to Vulcan. After this storyline, Vulcans began a cultural transformation that was presumably a turn toward the more enlightened Vulcans of Trek series set further in the future. For example, mind-melding before the ancient teachings were recovered was considered immoral; after, it was embraced as the legacy of all Vulcans. A two-part return to the Mirror Universe, made popular by The Original Series and Deep Space Nine, titled "In a Mirror, Darkly," was made late in the fourth season, which took place in the parallel dimension. These episodes use the Enterprise crew as the most barbaric members of the Terran Empire. As a sequel to the original Star Trek's "Mirror,Mirror" proved popular while "Part II" had an ending which was a cliffhanger. Had the series gone on for a fifth season, the story would have continued. The story was "continued" by means of the first "Mirror Universe" anthology published in 2007 by Pocket Books. The story, "Age of the Empress" was crafted by Mike Sussman, the writer of "In a Mirror, Darkly."
Romulans also stir up trouble midway through the season. While a diplomatic conference is hosted by Earth on the planet Babel, Romulans, using drone ships with holographic emitters (mimicking any ship) stir up trouble with the Andorians and Tellarites. This places the two races at each other's throats, and when they are revealed to be Romulan, Archer devises an alliance, similar to the Federation, with the Vulcans. This three-part arc, which presaged the inevitable Romulan-Earth War of 2156, received the lowest Nielsen ratings of the entire series, leading UPN to cancel it on February 2, 2005.
In the final story arc of the season a human terrorist group, called Terra Prime, are bent on removing all non-humans from human planets and genetically engineer a child from DNA samples of Commander Tucker and Commander T'Pol. They use the baby as a means to anger humans who have become afraid of aliens since the Xindi conflict and launch a campaign from Mars to drive the alien outsiders from human space. This storyline has been said by producers to represent how humanity must overcome its own bigotry and hatred in order to become the human race seen in later Treks.
The series cancellation was announced prior to the writing of the final episode of the fourth season allowing the writers to craft a series finale. This final episode, titled "These Are the Voyages...", aired May 13, 2005 in the United States and was one of the most heavily criticized episodes of the Star Trek franchise. Much of the criticism focused on the premise which essentially reduced the finale to a holodeck adventure from the Star Trek: The Next Generation series. The episode featured guest appearances by Jonathan Frakes and Marina Sirtis as their Star Trek: The Next Generation characters William Riker and Deanna Troi. Disregarding their eleven years of obvious aging, the episode is based during the TNG episode "The Pegasus". Brent Spiner lent his voice to the finale, and is briefly heard as Data. The last episode held the most views, but was the lowest rated episode of the series. T'Pol, played by Jolene Blalock voiced her negative opinion about bringing the two Next Generation actors to Enterprise.
 Plans for Season 5
At the time of its cancellation, planning for a proposed fifth season of Enterprise was underway. Most details of this never-made season come from comments made by producer Manny Coto who in 2009 stated that two arcs of this season may have been to show the 'origins of the Federation' and 'whispers of the Romulan war', and consequently, the Romulans would have been the major villains of the season.
Coto also stated that had the series been given a fifth season, the recurring Andorian character of Shran may have joined the Enterprise in an advisory role.
Other possible plans for the season included: an episode showing the construction of the first starbase; a Borg Queen origins story with Alice Krige as a Starfleet medical technician who makes contact with the Borg from Season 2's "Regeneration" and becomes the Borg Queen, and a Mirror Universe arc spanning four or five episodes.
There were also hopes for an episode in which T'Pol would finally meet her father and discover that he was in fact a Romulan agent who had posed as a Vulcan officer prior to faking his own death. The revelation that T'Pol was half-Romulan would have shed light on her affinity for humanity and as well as her interest in experimenting with emotions.
By the third season, ratings were continually declining, and the threat of cancellation loomed over Star Trek: Enterprise. This, along with the poor box office performance in 2002 of the film Star Trek Nemesis, cast an uncertain light upon the future of the Star Trek franchise in general.
Fans launched a letter writing campaign similar to the one that saved the third season of the Original Series. On May 20, 2004, it was announced that Enterprise had been renewed for a fourth season, but that the show would move from Wednesday to Friday nights. This move echoed the rescheduling of the original Star Trek to a Friday night time slot for its third season prior to its ultimate cancellation, as Friday nights have traditionally been considered "death row" for a major TV production.
Hired as a writer during the third season, Manny Coto was promoted to co-executive producer, becoming the series showrunner for the fourth season. Coto decided to retain the "arc" concept of season 3, but reduce it from one season-long arc to several "mini-arcs" of two or three episodes, with few standalones. The producers attempted to attract viewers by terminating a long-running story arc (the Temporal Cold War) and scheduling numerous episodes that served as prequels to storylines from The Original Series and The Next Generation.
Beginning in the summer of 2004, and continuing throughout the fourth season, there were reports that William Shatner would reprise the role of James T. Kirk or perhaps an ancestor in the series, but an agreement could not be reached.
The fourth season got off to a slow start in the ratings on October 8, 2004, due to the Friday time-slot, preemptions by local sports in some markets, and by coverage of the second presidential debate between George W. Bush and John Kerry in others. As well, Enterprise fans continued to indicate they chose to watch the weekend showing rather than the Friday broadcast, or chose to "time-shift" the program using their VCR or DVR equipment. In October 2004, it was announcedthat Enterprise was the 25th most popular Season Pass on the TiVo television recording system in the United States.
Speculation as to the future of the series came to an end on February 2, 2005, when UPN announced the series had been cancelled and its final episode would air on Friday, May 13, 2005. Fan groups such as "Save Enterprise" joined forces and announced a drive to raise money to finance a further season of Enterprise. Approximately $30 million was the goal of the campaign, based upon estimates of the cost for a full season cited by John Billingsley and others. In addition, Washington, D.C. lobbyist Dan Jensen circulated a letter on Capitol Hill in an effort to appeal to the sentiments of legislators. As a result, then Florida Congressman Mark Foley (R) agreed to sign the letter. The Washington "lobbying" effort garnered considerable press, and had a feature article on the front page of Roll Call.
Production of the fourth season concluded on March 8, 2005, and by the end of the month, Startrek.com was reporting the Enterprise sets had been taken down, marking the first time that Stage 9 at Paramount Studios has been without Star Trek sets since the late 1970s. The website did not indicate whether the sets have been preserved in storage (the industry term being 'fold-and-hold') or if they have been destroyed.
As of April 13, 2005, Paramount and UPN remained adamant that the cancellation of the series was final and that the studio was not interested in continuing the current incarnation of Star Trek. TrekUnited officials, however, still claimed to be in talks with Paramount over the future of the series at the time.
The website IGN Filmforce, reported on rumors Paramount had actually decided to cancel Enterprise after its fourth season as early as midway through the second year, quoted an unidentified "executive involved with Enterprise" as saying this scenario was "very likely".
Although widely reported as the death knell of the Star Trek franchise, the cancellation of Enterprise was followed within months by the announcement that Paramount was in pre-production on an 11th Star Trek feature film. After a false start involving Berman which would have set the film in a time period after the events of Enterprise but before TOS, Paramount recruited a new producing and writing team, which ultimately led to the release of a new Star Trek film film in May 2009. Like Enterprise, the new film (which did contain an indirect reference to the series: Scotty believes he has been "exiled" to the remote Starfleet outpost where Kirk and the older Spock encounter him as punishment for losing Admiral Archer's beagle- who Kirk is quite familiar with - in a transporter mishap) also adopted a prequel concept, with a different approach.