Romulan history
Romulan history describes the rise of the Romulan people from being a group of Vulcan emigrants to an interstellar empire.

Early history

A "Garden of Eden"-like place known as Vorta Vor was part of Romulan creation myths, similar to the Vulcan Sha Ka Ree. ()

One possible scientific explanation for the origin of Vulcans, and thereby also of the Romulans, came to light in 2268, with the discovery of Sargon and his people. When Sargon explained that his people had colonized many worlds in the galaxy half a million years ago, Spock theorized that  might have been such a colony world. According to Spock, "That would tend to explain certain elements of Vulcan prehistory." As of 2399, it was also theorized that the myth of Ganmadan might predate the arrival of the Vulcans' and Romulans' ancestors on Vulcan. (; ) In 2369, evidence was discovered that suggested many of the galaxy's humanoid races were descended from a single humanoid race, the originators of the shared basic anatomy. Around 4.5 billion years ago, they had seeded many worlds with a DNA code to guide evolution to a form resembling their own. Romulans, and therefore also Vulcans, displayed evidence of these DNA sequences. () 

Vulcans were once an extremely violent and emotional people, waging almost constant warfare amongst each other. (; ) As their technology improved, the Vulcans eventually reached a point where their violent nature threatened the extinction of their species. (; ) Around 370 AD, the philosopher Surak led his people in a great reformation to embrace logic and pacifism, a period called the Time of Awakening. One group, known as "those who march beneath the Raptor's wings", rejected Surak's teachings and fought against his followers. (; ; ) In the end, the dissidents lost an ensuing, terrible atomic war and left their homeworld. During their travels, some split away to form the Debrune civilization, which became extinct long before the 24th century. Eventually, the group settled on two planets named Romulus and Remus, and thus laid the foundation of the Romulan civilization. ()

According to Q, one of Quinn's "self-destructive stunts" created a misunderstanding which ignited "the hundred-year war between the Romulans and the Vulcans." ()

Centuries before the 24th century, a group of Romulans discovered an ancient encoded message on Aia, a planet in an artificially created octonary star system. The message, which was intended for synthetic lifeforms and called upon them to destroy their creators, prompted the formation of the Zhat Vash, a secret Romulan cabal dedicated to eliminating synthetic lifeforms. ()

According to Admiral Dougherty, it was warp drive that turned "a bunch of Romulan thugs into an empire." Dougherty likened the impact of warp technology on the Romulans to that of petroleum on "petty thugs" on Earth in the past. ()

22nd century

First contact with Humans

As of 2152, Vulcan Subcommander T'Pol claimed that the Vulcan High Command had never made direct contact with the Romulan Star Empire, but merely heard rumors about them being aggressive and territorial. ()

The Romulan Empire's first recorded contact with Humans occurred in 2152 when the Starfleet vessel Enterprise NX-01 was on course to explore an M-class planet. Initially unknown to Enterprise, the planet was claimed by the Romulans. The ship was damaged by a cloaked spatial mine, part of a Romulan minefield surrounding the planet. A decloaking  subsequently established audio communication and, although the universal translator initially had problems to lock on to the Romulan language, Enterprise communications officer Hoshi Sato was able to translate what turned out to be an ultimatum to depart immediately. After successfully detaching a spatial mine that latched on to the ship's hull, Enterprise left the system. ()

Infiltration of Vulcan

As of 2154, the Romulan Star Empire was covertly collaborating with Administrator V'Las of the Vulcan High Command. This was part of a decades-long effort to "reunify" the Romulan and Vulcan "cousins", presumably under Romulan rule, by politically isolating Vulcan. However, a group of Vulcans named Syrrannites accused the High Command of no longer following the logical teachings of Surak and, thus, were a threat to the Romulan plans of reunification. Secretly working with Major Talok, a Romulan deep-cover agent who had infiltrated Vulcan several years earlier and now worked within the Vulcan High Command, V'Las assumed a very aggressive stance and framed the Syrrannites for a terror attack on the United Earth Embassy on Vulcan.

Also calling for a preemptive strike against Andoria, the conspiracy ultimately led to the Battle of Andoria between Vulcan and the Andorian Empire in mid-2154. However, V'Las was deposed after he was eventually identified as being behind the embassy bombings and the exaggerated war claims against the Andorians. Although Talok then promised him that this would be but a minor setback, he subsequently left Vulcan. ()

The Babel Crisis

As it was mainly due to the Earth starship Enterprise and its crew that the Romulan plot had been thwarted, it became more evident for the Star Empire that the Humans were rising as a regional power. United Earth practiced a mediating, even unifying, influence on its neighbors, so the prospect of an alliance contrary to Romulan interests led to their covert attempts to destabilize the region and the fragile peace.

Therefore, Admiral Valdore, with the support of Senator , precipitated the "Babel Crisis" by deploying telepresence-operated drone ships equipped with chameleon-like camouflage systems. Though briefly wreaking havoc on regional shipping and diplomacy, the Romulan effort ultimately failed. A temporary alliance of Human, Vulcan, Andorian and Tellarite starships thwarted the drone ship threat, prompting closer diplomatic relations that led to talks, in 2155, on forming a Coalition of Planets. ()

Earth-Romulan War and isolation

Relations between Romulans and United Earth deteriorated into open war in the following years. Beginning in 2156, the Earth-Romulan War was fought without any kind of personal or visual interaction between the two sides, preventing Humans or allies from fully understanding the nature of their opponent. Following a humiliating defeat at the Battle of Cheron in 2160 at the hands of a Human/Vulcan/Andorian/Tellarite alliance, the Romulans negotiated a treaty via subspace radio, establishing a neutral zone between the Star Empire's sphere of influence and territory that was about to fall under the jurisdiction of the soon-to-be-formed United Federation of Planets. (, ; )

For the next century, Romulans isolated themselves from Human and Federation affairs. However, they remained very active within their own sphere of influence, fighting numerous campaigns. ()

23rd century

From isolation to standoff

In 2266, the Neutral Zone Incursion by the Romulan Star Empire marked the end of a century of isolation from the Federation. Emerging from seclusion to test the strength of the empire's old enemy as well as to field test new technologies of its own, the Romulan Praetor ordered his finest flagship, a Romulan Bird-of-Prey led by an experienced commander, to violate the Neutral Zone and attack a series of Federation outposts that lined the border, in Sector Z-6. Equipped with an effective cloaking device and a powerful new plasma torpedo system, the Bird-of-Prey easily annihilated Outposts 2, 3, 4, and 8. The ship's commander voiced his concerns to his centurion that a victorious homecoming, revealing Federation weaknesses, could push the Empire into another war, but the marauding Romulan vessel was intercepted and defeated by the  before success could be reported.

The incident ended with a visual communication in which the Romulan commander bestowed his respect to Captain Kirk of the Enterprise. This also marked the Federation's first confirmed visual observation of the Vulcan-like Romulan appearance. ()

A brief but ultimately unsuccessful thaw in relations occurred in 2267 between the Romulan Star Empire, the Klingon Empire, and the Federation, with the founding of a jointly managed colony on Nimbus III. Dubbed the "planet of galactic peace", the colony quickly became an embarrassing failure for all three governments, although regular meetings between representatives did take place at the colony for at least the next twenty years. ()

In 2268, a devastating polaric ion device explosion resulted in the destruction of a Romulan research colony on Chaltok IV. Following this incident, the Polaric Test Ban Treaty, banning research on polaric energy, was signed. ()

Within that same year, Captain Kirk was ordered to take the Enterprise into the Neutral Zone, thereby provoking an encounter with Romulan forces in an attempt to steal a functional cloaking device so that Starfleet could assess its danger to the Federation. After the unsuccessful Neutral Zone Incursion two years earlier, the Romulans vigorously patrolled their side of the Neutral Zone, and further encounters with trespassing Starfleet vessels were countered by the Star Empire by simply outnumbering their opponent. As a result, the Enterprise was quickly intercepted and detained by three Romulan vessels, among which there were at least two  ships of Klingon design now being used by the Star Empire. By faking his death, Kirk was able to infiltrate one of the Romulan ships, steal their cloaking device, and subsequently use it on the Enterprise to escape to Federation space along with a captured Romulan commander. ()

In 2269, the Romulans violated a Romulan-Federation treaty by utilizing a shapeshifting Vendorian to lure the Enterprise into the Neutral Zone in order to seize the spacecraft. However, the Starfleet ship was able to defeat two Romulan battle cruisers and return to Federation space. () In 2270, three Romulan ships attacked the Enterprise within Federation territory, but the latter craft again proved victorious and no major hostilities followed. ()

Klingon interactions and Khitomer conspiracy
See also: Romulan-Klingon relations
Whereas in 2268 cloaking technology was considered to be uniquely Romulan, the following year the Klingon ship  was assumed to possess an effective cloaking device. In 2271, the Romulans suffered a significant defeat at the Battle of Klach D'kel Brakt (the "Briar Patch") at the hands of Klingon forces led by Kor. By 2292, Romulans and Klingons regarded each other as "blood enemies". (; ; ; ; )

In 2287, the Romulan ambassador to Nimbus III, Caithlin Dar, was briefly taken hostage alongside her Klingon and Federation colleagues by the so-called "Galactic Army of Light". Eventually, the crisis was resolved by an unusual cooperation between the  and an initially pursuing Klingon ship. ()

In 2293, the destruction of the Klingon moon Praxis caused an ecological and economical disaster in the Klingon Empire, bringing about a fundamental shift of power in the quadrant. When the Chancellor of the Klingon High Council, Gorkon, took the controversial move of proposing a full peace treaty with the Federation, the Romulan government, while officially remaining neutral, attempted diplomatic subterfuge to prevent such a situation, as it would be highly unfavorable for the Star Empire. 

The Romulan ambassador to Earth, Nanclus, became part of a conspiracy, which also included conservative members of Starfleet as well as the Klingon Empire, and cautiously tried to escalate the situation by advising the Federation President to execute Operation Retrieve. Although the conspiracy was able to assassinate Chancellor Gorkon, it was ultimately uncovered and proved unsuccessful in sabotaging a lasting Federation-Klingon peace treaty. () It became a defining Romulan motive of the following decades to re-shift the balance of power by perturbing this peace. ()

24th century

Opposition to the Federation

Escalation and renewed isolation
Intermittent hostilities between the Romulan Star Empire and the Federation continued into the 24th century. A notable example was the Norkan Campaign led by Admiral Alidar Jarok, which the Federation considered to be a massacre. In 2311, the Tomed Incident between the Romulans and the Federation cost thousands of lives and led to the Treaty of Algeron, which set the foundation for a lasting period of peace. The treaty forbade the Federation from developing cloaking technology and clarified that violations of the Romulan Neutral Zone without adequate notification, by either side, would be considered an act of war. (; ) 

As had happened 150 years earlier, the empire returned to a policy of isolation from the Federation after the Tomed Incident, turning their attention to "matters more urgent." This period of "isolation" was not hermetic, however, and limited, indirect contact between both sides continued: In 2344, survivors from the , including Natasha Yar, who later became the mother of Commander Sela, were secretly captured by the Romulans; in 2349, Starfleet officer DeSeve defected to the Star Empire, allegedly being attracted by the Romulans' "strict moral compass" and their "absolute certainty about the purpose of life". ()

Cold war

The Romulans began emerging from their isolation in 2364. First, a Federation border outpost reported that seven Romulan battle cruisers had entered sensor range, prompting a response by the . () Later that year, a warbird under Commander Tebok was dispatched to investigate the mysterious destruction of border outposts along either side of the Neutral Zone. Tebok confronted Captain Jean-Luc Picard of the  on the Federation side of the Neutral Zone. It was determined that neither side had been responsible for the attacks, which, unknown at the time, were caused by the Borg. After fifty-three years, seven months, and eighteen days of no official contact, the Romulan Star Empire subsequently resumed an active, oppositional interest in Federation affairs. ()

In 2366, the Romulan scoutship  crash-landed on Galorndon Core, in Federation space. The Enterprise investigated the wreck and initially rescued one survivor, Patahk. Commander Tomalak, claiming the crash of the Pi to be an accident, demanded Patahk's return and eventually crossed the Neutral Zone to retrieve him. The incident nearly escalated to war after Patahk died of his injuries, but was defused after the Enterprise recovered and repatriated a second Romulan survivor, Centurion Bochra. ()

Later that year, the Neutral Zone was again violated, by a scoutship piloted by Admiral Alidar Jarok. Jarok's intent was to defect to the Federation, so as to avert an impending Romulan invasion that was to be launched from a secret base on Nelvana III. Jarok had in fact been a victim of a misinformation campaign by Tomalak, who aimed to expose him as a traitor and lure the Enterprise into the Neutral Zone so that it could be captured. Although the Enterprise was able to withdraw from the situation with the timely intervention of hidden Klingon reinforcements, Admiral Jarok ultimately chose to commit suicide. ()

By 2367, Romulan forces were deployed in an aggressive posture along the Neutral Zone, which Starfleet believed was to support a strategy of testing Federation defenses. An overture to discuss the normalization of diplomatic relations between the two powers that year was found to be a Romulan ruse, however. In fact, the Star Empire was able to achieve a major intelligence victory, when the Devoras under Admiral Mendak successfully extracted, from Federation space, Sub-Commander Selok, who had, until then, been impersonating the Vulcan , one of the Federation's most distinguished ambassadors. ()

Competitive research in technologies and phenomena of potential strategic value remained one of the main battlegrounds of the Romulan-Federation stand-off. In 2366, two  warbirds were dispatched to outrun the Enterprise-D to make contact and potentially capture a powerful spaceborne lifeform, with one of them attacking the Enterprise in order to reach the lifeform first. The mission failed, however, and resulted in the destruction of one of the warbirds. () In 2368, a Romulan science ship suffered a major malfunction while field testing an interphase cloaking device, which would allow a vessel to pass through solid matter. The incident was a particular setback, as the ship's distress call was answered by no other than Starfleet's Enterprise-D. Despite the assistance given by Starfleet to the damaged science ship, the Romulans still attempted to destroy the Enterprise, though their plan was discovered and failed. () 

In 2369, Romulan ships shadowed the Enterprise-D and eventually participated in the discovery of the humanoid progenitor race. Moved by this revelation, the Romulan commander contacted the Enterprise and pointed out the fundamental similarities between Romulans and Humans. () Later that year, the Enterprise answered another Romulan distress call from a warbird whose singularity power source was compromised by singularity-dwelling lifeforms. Although the crew of the warbird was rescued, the lifeforms eventually took the ship into a different space-time continuum. () In 2370, the Terix uncovered illegal Federation experiments into a phasing cloaking device in the Devolin system. Commander Sirol was subsequently hailed by Starfleet, being assured that the Romulan government would soon be contacted concerning the recent incident and that the experiment was not sanctioned by the Federation. () As of 2371, the Romulans were experimenting with trilithium, a high-grade explosive, but were unable to stabilize it. When a batch of Romulan trilithium was stolen, the Romulans did not hesitate to attack the Federation's Amargosa observatory during their search for it. As of 2375, trilitihium isotopes were found in Romulan plasma torpedoes. (; )

Both diplomacy and confrontations between the Star Empire and the Federation continued during the early 2370s. In 2372, the high-level Antwerp Conference between the two powers took place on Earth but was disrupted by a bombing. () A year later, Starfleet officially used the fear of Romulan aggression to order the  to patrol the Neutral Zone, although the last unusual Romulan activity in this area had been nine months prior. ()

Vulcan reunification movement

There had long existed an underground movement of Romulans interested in Vulcan culture and philosophy, who desired to eventually reunite with their distant cousins. Despite being declared enemies of the state, the unification movement grew in strength during the 24th century. The cause of unification appeared to near a breakthrough in 2368, with the rise of Proconsul Neral, who seemed receptive to the possibility of unification. Senator Pardek, a long-time ally of the unification movement, invited Ambassador Spock to Romulus to address the opportunity for peace.

However, Pardek had, in fact, betrayed the unification movement at the behest of Neral and Commander Sela. Sela sought to use the unification movement and Spock's credibility to disguise an attempted invasion of Vulcan using three stolen Vulcan transports. Spock, Captain Jean-Luc Picard, and Lieutenant Commander Data managed to expose the conspiracy, leading the Romulans to destroy their own invasion force rather than allowing it to be captured by Starfleet. () Spock remained on Romulus to support the underground movement. In 2369, the movement kidnapped Starfleet officer Lieutenant Commander Troi and used her to infiltrate the  in order to arrange for the defection of Vice-Proconsul M'ret, who had spoken out against the repressive policies of the Romulan government, to the Federation. ()

USS Voyager
The Romulans encountered personnel from the Federation starship , stranded in the Delta Quadrant, on two occasions. Lieutenant Reginald Barclay claimed, in 2377, that the Romulans had "been interested in Voyager for years." ()

In 2351, the science vessel Talvath, commanded by Doctor Telek R'Mor, came into contact with Voyager twenty years in the future through a micro-wormhole in Sector 1385. R'Mor agreed to deliver letters from the Voyager crew to their families at the appropriate time, but because he died in 2367, he was unable to do so. It was, however, remarked that the data chip R'Mor had been given possibly had been passed on to other Romulan officials, therefore precipitating a certain knowledge of Voyager and its fate. () When he visited Voyager in 2373, the omnipotent entity Q also claimed that he could have mated with the Romulan Empress for the purpose of creating offspring. () Voyager was also responsible for the failure of a 2374 Tal Shiar operation, led by Rekar, to steal the experimental . The Voyager crew had transmitted their EMH through a Hirogen communications network to the Prometheus in an attempt to communicate with Starfleet. Once aboard, the Voyager EMH cooperated with the Prometheus EMH Mark II to incapacitate the Romulans and assist a Starfleet task force in reclaiming the ship. ()

Hot and cold conflicts with the Klingon Empire
See also: Battle of Narendra III, Khitomer Massacre, Klingon Civil War

The apparent vicissitude of Klingon-Romulan relations during the 23rd century propagated into the 24th century. In 2344, four Romulan warbirds attacked the Klingon outpost on Narendra III. The , answering the Klingons' distress call, fought a futile defense against the Romulans and was also destroyed. Ironically, the self-sacrifice of the Enterprise reversed the trend of deteriorating relations between the Federation and the Klingon Empire, to the Romulans' detriment. () Two years later, in 2346, at a time when it was supposed to be "an ally" of the Klingons, the Star Empire attacked the Klingon planet Khitomer and killed almost all 4,000 colonists. The raid was made possible by the traitor Ja'rod of the House of Duras, who supplied the Romulans with the deactivation codes of the colony's defensive shields, although this treason was later blamed on another colonist, Mogh. Twenty-years after the incident, Worf, son of Mogh, discovered a Romulan prisoner camp on Carraya IV in the hopes of finding his father there. After learning that Mogh had died in the original attack, Worf agreed to keep the camp a secret as the Klingon prisoners had adapted to a peaceful coexistence with the Romulan guards and thereby dishonored themselves. () In 2350, Romulan forces failed in an attempt to board Klingon General ShiVang's flagship. That same year, later Romulan Praetor Neral's family was killed in a Klingon attack. ()

In 2367, the Romulans engaged in concerted efforts, led by Commander Sela, to break the Federation-Klingon alliance and shift the balance of power in the quadrant in their favor. () The influential House of Duras, with its long-standing ties to the Romulans, provided the best opportunity, as Duras was a leading candidate to succeed the ailing Chancellor K'mpec as leader of the Klingon Empire. After K'mpec's death, Romulan equipment was involved in Duras' attempt to assassinate his rival, Gowron, during the Rite of Succession. However, Duras was killed by Lieutenant Worf in vengeance for the murder of Ambassador K'Ehleyr. ()

Aside from the House of Duras, the Star Empire was able to recruit other Klingon individuals who were opposing their alliance with the Federation and believed a partnership with Romulus would make their people stronger. In late 2367, Klingon exobiologist J'Dan, who was part of an exchange program aboard the Enterprise-D, turned out to be spying for the Romulans. () Some weeks later, Commander Sela was cooperating with Klingon Ambassador  in an attempt to foment rebellion on the Klingon colony of Krios and blame it on the Federation. The Romulans supplied counterfeit Federation phasers to the Kriosian rebels and abducted Lieutenant Commander Geordi La Forge, whom they brainwashed to assassinate Vagh, the Klingon governor of Krios. Enterprise personnel were able to prevent the assassination and expose the Romulans' involvement. ()

Near the end of 2367, the Romulans, specifically Commander Sela, secretly backed Duras' sisters, Lursa and B'Etor, in their bid to take over the Klingon Empire via Toral, an illegitimate son their late brother had had. In an ensuing Klingon Civil War, Romulan supplies enabled the forces of the Duras sisters to make advances against those of Gowron. Captain Jean-Luc Picard suspected Romulan interference in the war and led a fleet of twenty-three starships to blockade the Klingon-Romulan border. Through the efforts of Lieutenant Commander Data on the , a convoy of Romulan supply ship 002s was exposed, forcing Sela to order her ships back to Romulan territory. Without Romulan support, the Duras sisters lost the war and were forced to flee. ()

Romulan-Klingon tensions continued to exist over the next years. (; ) In 2371, the renegade Duras sisters raided a Romulan outpost to acquire weapons-grade trilithium. () The next year, several outposts along the Romulan border were attacked by the Klingons. ()

Dominion War
Main article: Dominion War
 
In late 2370, contact with the Dominion, a hegemonial power from the Gamma Quadrant ruled by the "Founders", led to the first thaw in the Star Empire's relations with the Federation. The Romulans regarded the Dominion as the greatest existential threat to emerge in the past century, but were unwilling to send any ships to the Gamma Quadrant via the Bajoran wormhole themselves. Instead, in exchange for intelligence gathered regarding the Dominion, in 2371, the Romulans permitted the use of a cloaking device on the , which was to be used only in the Gamma Quadrant and operated and guarded by a Romulan liaison officer. Some months later, two official Romulan diplomats, Ruwon and Karina, as well as a secret, cloaked warbird, were dispatched to Deep Space 9, the Bajoran-Federation space station at the mouth of the Bajoran wormhole. The diplomats were unimpressed with the eventual intelligence data they were provided with and suspicious of the station's security chief, Odo, failing to see the distinction between "Changeling" and "Founder". In fact, the entire diplomatic mission was but a cover to carry out the actual Romulan plan – to end the Dominion threat by using the warbird to destroy the wormhole along with Deep Space 9 in order to discard of any witnesses. However, the ploy was uncovered as the cloaked warbird was discovered, and Ruwon and Karina had to leave the station. ()

Nevertheless, through their agreement with Starfleet, the Romulans had already learned of the Founders, their control of the Jem'Hadar through ketracel-white, and the location of . () Still poised to end the Dominion threat once and for all, the Romulan intelligence service Tal Shiar conspired with the Cardassian Obsidian Order to launch a joint attack on the Founders' homeworld in the Omarion Nebula. By annihilating the Founders, it was estimated that the Jem'Hadar would weaken and die out in a matter of days, as their supply of ketracel-white would run out. However, the Tal Shiar had been infiltrated by , who had actually supported the plan as a unique opportunity to wipe out or substantially weaken the Tal Shiar as well as the Obsidian Order – ruthless organizations with the potential of being a threat to the Dominion. A battle in the Omarion Nebula resulted and proved catastrophic for both fleets, and although a small number of Romulans survived and was imprisoned at Internment Camp 371, all five Romulan warbirds involved in the battle were destroyed. ()

When the Dominion gained a major foothold in the Alpha Quadrant through the incorporation of the Cardassian Union in 2373, the Romulans dispatched a fleet of warbirds to Deep Space 9 in anticipation of an imminent Dominion attack, joining the Klingon and Federation forces there. () However, after war did not immediately break out, the Romulan Senate eventually opted to sign a non-aggression pact with the Dominion. () The pact was negotiated by Senator Vreenak, who remained an ardently pro-Dominion voice in the Romulan government. ()

The Romulans thus did not participate in the early months of the Dominion War, though some analyses suggested that they would eventually join the war against the Dominion. () Nevertheless, the Romulans were turning a blind eye to Dominion forces crossing their space to ambush Federation ships. Concluding that the war could not be won without Romulan involvement, Captain Benjamin Sisko and Elim Garak undertook a covert operation to convince the Romulans that the Dominion posed an imminent threat. To that end, Vreenak was presented with an optolythic data rod containing a forged holographic record of a secret meeting showing Dominion officials Weyoun and Legate Damar discussing an invasion of the Romulan Empire. Although Sisko hoped the fake recording would pass and convince the senator, an infuriated Vreenak uncovered the plot and headed back to Romulus. However, the operation ended with the assassination of the senator by sabotaging his shuttle. As Garak had originally foreseen, the Romulans discovered the data rod, but ascribed any imperfections to the blast damage, and therefore blamed the Dominion for the assassination. ()

In the wake of Vreenak's death and the discovery of apparent Dominion invasion plans, the Romulan Star Empire formally declared war, joining the Federation Alliance. Within hours, Romulan forces attacked fifteen bases along the Cardassian-Romulan border, opening up a new front and relieving pressure on the Federation and Klingon lines. () Further Romulan engagements soon followed, including the liberation of the Federation world Benzar, which had earlier been occupied by the Dominion (), as well as twelve successful campaigns led by Shinzon of Remus. The Romulans often employed Reman shock troops in the most violent encounters. ()

The Romulans soon sent representatives, first Senators Letant and Cretak, then General Velal, to coordinate war plans with their new allies, and eventually established a permanent presence on Deep Space 9. () Interactions between the formerly adversarial powers, though, remained fractious, and the Federation was often forced to mediate disputes between the Romulans and the Klingons. () At one point, an attempt by the Romulans to place heavy weapons on the Bajoran moon Derna nearly shattered the alliance. () 

In general, however, diplomatic relations between the Romulans and the Federation improved during the war. In 2375, the Federation embargo on Romulan ale was lifted, and a Romulan-Federation conference took place on Romulus. On the other hand, both sides were aware that they would be rivals for influence in the quadrant once the Dominion was defeated. Espionage and covert operations were rampant, including an effort by Starfleet and Section 31 to place a Federation agent on the powerful Romulan Continuing Committee. ()

Romulan forces were involved in most major battles in the later parts of the Dominion War, including the first and second battles in the Chin'toka system as well as the final push against Cardassia Prime. The latter saw the destruction of the Romulan flagship and was pushed for by the Federation and the Klingon Empire, despite an initial hesitation of Romulan representative Velal, who thought it would be wiser to contain the Dominion, rather than to mount a major offensive. () After the Federation Alliance was victorious at Cardassia in late 2375, a female Romulan dignitary represented the Star Empire at the signing of the Treaty of Bajor on Deep Space 9, which formally brought the Dominion War to a conclusion. ()

Reman coup d'état 

Following the Dominion War, Romulan-Federation relations cooled off again, a minor side-effect being the reintroduction of the ban on Romulan ale in the Federation, which had temporarily been lifted during the war. By 2379, a schism had developed between the Romulan Senate and the military over whether the empire should seize the opportunity of a weakened Starfleet to invade the Federation. During this time, Shinzon, a Human clone of Captain Jean-Luc Picard originally intended for infiltrating Starfleet, emerged as the leader of a powerful Reman force, wielding new technologies, including an improved cloaking device and a thalaron radiation weapon. Shinzon enlisted the support of Commander Suran and Senator Tal'aura by promising to conquer Earth. At a session of the Romulan Senate, after Praetor Hiren rejected Suran's proposal to ally with Shinzon, as expected, Tal'aura planted a thalaron radiation device that assassinated the rest of the Senate.

Shinzon installed himself as the new praetor and invited the Enterprise-E to Romulus for peace talks. However, his gesture was a mere ruse for the purpose of capturing Picard, as he needed a transfusion from Picard to heal his body, which was rapidly deteriorating. Picard and the Enterprise escaped, pursued by Shinzon aboard his flagship Scimitar, while Commander Donatra was able to convince her superiors that they could not support the genocidal ambitions of Shinzon, who now planned to use the Scimitar's thalaron weapon on Earth. Donatra led two warbirds in support of the Enterprise while it battled with the Scimitar in the Bassen Rift. Ultimately, Shinzon and the Scimitar were both destroyed. The succeeding Romulan government made genuine overtures of peace toward the Federation, which was hoped would usher in a new era of understanding and peace between the two powers. The  was thereafter dispatched to the Romulan Neutral Zone to serve as the command ship for a diplomatic task force. ()

Destruction of Romulus 

In the mid-2380s, the Romulus system's star threatened to go supernova and annihilate Romulus. The Romulan government requested the Federation's aid in evacuating the system, which was initially granted. With now Admiral Jean-Luc Picard being a strong pro-Romulan voice, Starfleet began constructing a fleet of ten thousand  ferries to help transport 900 million Romulan citizens away from the star's blast radius. This was not without controversy: apparently incensed that the Federation had agreed to devote such considerable resources to aid an enemy, fourteen member species threatened to leave the Federation if the Romulans were not left to their fate. Despite this, Federation efforts to support the Romulan evacuation proceeded and the planet Vashti was selected as a relocation hub, where the order of the Qowat Milat alone helped to relocate 250,000 refugees. ()

Ultimately, however, an attack on Mars carried out by re-programmed synths in 2385 destroyed the evacuation fleet before it could depart for Romulan space, and Starfleet subsequently withdrew their promise to help. The attack had been orchestrated by Oh of the Zhat Vash, a secret, centuries old Romulan cabal operating within the Tal Shiar that was dedicated to destroying any kind of artificial lifeforms, which they considered bringers of Ganmadan, an ancient Romulan apocalyptic myth. Oh's plan of thus pushing the Federation towards a ban of artificial lifeforms was successful and she went on to infiltrate Starfleet's command structure, eventually becoming Chief of Starfleet Security. (; )

In 2387, shortly before the Romulan sun was due to explode, Ambassador Spock pledged to save Romulus by using red matter to create a black hole that would absorb the explosion. However, while he was able to contain the supernova before it could threaten the Milky Way Galaxy as a whole, Spock arrived too late to prevent the destruction of Romulus. Among the dead were the wife and unborn child of Nero, a Romulan miner who blamed the disaster on Spock and the Federation. A grief-stricken Nero referred to himself as the "last of the Romulan Empire" and intercepted  with his mining ship, the Narada. Both vessels along with their crews went missing, as they were pulled into the black hole created by the red matter (see alternate reality). ()

Reorganization and continued Zhat Vash activities 

In the aftermath of the supernova, Romulan refugees lived dispersed. While some, such as former Tal Shiar members Laris and Zhaban, migrated to Earth, many, including ex-senator Tenqem Adrev and the Qowat Milat, made a living on the former relocation hub of Vashti, which also became a hotbed for the nationalistic and racist "Romulan Rebirth movement". Backed by the Tal Shiar, a new political entity succeeding the Star Empire was the Romulan Free State, which controlled a derelict Borg cube called the , from which it freed Borg drones and derived profit through the exploitation of Borg technology. Although the Tal Shiar still fielded at least several hundred s, the Romulan Neutral Zone effectively ceased to exist and some areas like the Qiris sector became lawless, enabling activities by warlords such as Kar Kantar. ()

In 2399, the Zhat Vash continued their quest against artificial lifeforms by finding the location of Coppelius, a secret colony of androids founded on Ghulion IV in response to the Federation's synth ban from 2385. While an attempt to kidnap one unknowing Coppelius android living on Earth failed, they infiltrated the Borg Reclamation Project, where the information was successfully extracted from another unknowing android working there despite causing a serious disruption of the reclamation project. As operative Oh and a fleet of 218 Warbirds eventually closed in on Coppelius, however, they were stopped and forced to return to Romulan space by La Sirena commanded by Jean-Luc Picard as well as a Federation fleet led by Captain William T. Riker. The latter subsequently put Ghulion IV under Federation protection under the terms of the Treaty of Algeron. ()

Post-24th Century 
At some point several centuries after Spock's apparent death, his efforts to reunify the Vulcan and Romulan peoples finally bore fruit. The reunified society settled on their ancestral homeworld of Vulcan, re-named Ni'Var. () Despite occasional tensions, this union remained intact until at least the late 32nd century.

Alternate timelines
In the anti-time present of 2370, at least thirty Romulan warbirds were pulled from other assignments and ordered towards the Neutral Zone to investigate the Devron system, causing Starfleet to issue a fleet-wide yellow alert and deploy fifteen starships along the Neutral Zone itself. After the anti-time eruption had been destroyed, no unusual Romulan activity was observed. ()

In an alternate timeline caused by the Defiant accidentally sending three officers into Earth's past, the Federation never came to be. When the crew of the Defiant in 2371 scanned for Federation and alien outposts, all they could find were Romulan transmissions detected in the vicinity of Alpha Centauri. ()

In the anti-time future, Romulus had not been destroyed by a supernova, but the Romulans had been defeated by the Klingon Empire as of 2395. As a result, their territory was occupied by the Klingons, and the Neutral Zone abolished. Around 2395, tensions were rising between the Klingons and the Federation, and no Starfleet ships were allowed to enter former Romulan space. However, due to an outbreak of Terrellian plague on Romulus, the Klingons permitted Federation medical ships to cross the border. ()

Mirror universe 
When Benjamin Sisko visited the mirror universe in 2371, he initially tried to cover his departure from that universe by telling  that he would visit the Romulans in an attempt to solicit assistance for the fledgling Terran Rebellion in their fight against the Klingon-Cardassian Alliance. ()

Alternate reality 

After they were pulled into the red matter black hole in 2387, the Narada and Spock's vessel emerged in the years 2233 and 2258 of an alternate reality, respectively. Upon encountering the Narada in 2233, Starfleet initially interpreted Nero's aggression as an act of war by the Romulan Empire. Quickly, a conference with the Federation and Romulan leadership at a neutral location was offered, but Nero declined and emphasized that he was not affiliated with the Romulan Empire (of that era). As of 2258 in this reality, the Federation had become aware of the Romulans' common ancestry with the Vulcans and  was knowledgeable on all three dialects of their language. Although Nero subsequently managed to annihilate  during his vendetta against Spock, he was eventually killed when the Narada was destroyed in another red matter black hole, created by a collision with Spock's ship. ()

Timeline
370: Time of Awakening on  – As the planet is consumed by atomic wars, Surak proposes to embrace logic as a way to peace. "Those who march beneath the Raptor's wings" oppose his views and leave the planet after losing the war. Whereas some become the ancestors of the Debrune, others settle Romulus, laying the foundation of the Romulan civilization.
2152: First contact with Humans occurs as the Earth Starfleet vessel  accidentally enters a Romulan minefield.
2154: The Romulan Star Empire has infiltrated the Vulcan High Command, but fails at its attempt to facilitate an eventual re-unification by isolating Vulcan. After this approach is thwarted and the Vulcan government toppled, Admiral Valdore fails at another attempt to sabotage the emerging alliance between the Humans and their Andorian, Vulcan, and Tellarite partners.
2156-2160: Earth-Romulan War – The conflict with the Humans escalates into an open war, which is concluded with a humiliating defeat for the Romulans at the hands of an Earth/Vulcan/Andorian/Tellarite alliance at the Battle of Cheron. Without visual communication, a neutral zone between the two power blocs is agreed on and the Star Empire begins a period of isolation from the soon-to-be-formed Federation.
2266: Neutral Zone Incursion – The Star Empire emerges from seclusion as the Romulan praetor orders his flagship to violate the Neutral Zone. However, the vessel is defeated by the , under Captain Kirk, and the first official visual communication between both sides confirms the Vulcan-like physical appearance of the Romulans.
2267: The Romulan Star Empire, along with the Federation and the Klingon Empire, jointly, but ultimately unsuccessfully, colonize Nimbus III, which is dubbed the "Planet of Galactic Peace".
2268: In order to assess its danger to the Federation, Kirk and the Enterprise violate the Neutral Zone and manage to steal a cloaking device as well as to capture a Romulan commander. As of this encounter, the Romulans are employing ships of Klingon design. Also during this year, a polaric ion explosion destroys a Romulan research colony on Chaltok IV, prompting the Polaric Test Ban Treaty.
2271: Battle of Klach D'kel Brakt – The Star Empire suffers a significant defeat at the hands of Klingon forces under Commander Kor.
2287: Romulan ambassador to Nimbus III, Caithlin Dar, is briefly taken hostage by the renegade "Galactic Army of Light."
2292: By this year, Romulans and Klingons regard each other as "blood enemies".
2293: Khitomer Accords – Despite diplomatic sabotage involving the Romulan ambassador to Earth, Nanclus, the balance of power around the Star Empire is fundamentally shifted when the Federation and the Klingon Empire negotiate for a lasting peace.
2311: Tomed Incident – A terrible confrontation between the Star Empire and the Federation leads to the signing of the Treaty of Algeron, re-enforcing the Neutral Zone, banning Starfleet from any research into cloaking technology, and driving the Romulans back into isolation.
2344: Battle of Narendra III – Romulan ships attack the Klingon colony on Narendra III. Answering the distress call, the Federation starship  is outmatched but honorably sacrifices itself, thereby fostering Federation-Klingon relations. Survivors of the Enterprise are subsequently taken to Romulus; among them is Natasha Yar, who will later become the mother of Commander Sela.
2346: Khitomer Massacre – At a time they are supposed to be "allies" of the Klingon Empire, the Romulans attack another Klingon colony, this time on Khitomer. The attack kills 4,000 colonists and has been made possible by Ja'rod of the House of Duras, who helps to disable the planetary defense system.
2350: Romulan forces fail in an attempt to board Klingon General ShiVang's flagship. That same year, later Romulan Praetor Neral's family are killed in a Klingon attack.
2364: After fifty-three years, the Star Empire ends its isolation from the Federation and agrees on limited cooperation to determine the cause of destruction to bases on both sides along the Neutral Zone.
2366: Several tense encounters between Starfleet and Romulan forces, including the failed defection of Admiral Alidar Jarok, occur along the Neutral Zone and in unclaimed space.
2367: The Star Empire deploys its forces in an aggressive posture along the Neutral Zone and successfully extracts one of its operatives impersonating Federation ambassador . Later that year, Commander Sela steps up Romulan efforts to sabotage the Federation-Klingon alliance. While her assassination attempt on Governor Vagh is foiled by the crew of the , she starts to covertly influence and support the anti-Federation House of Duras during the Klingon Civil War.
2368: Starfleet cuts off Romulan support for the House of Duras, causing their quick defeat in the Klingon Civil War and thwarting the Star Empire's plan to destabilize the Klingon-Federation alliance. Shortly afterwards, Proconsul Neral's support for an underground Romulan-Vulcan reunification movemement and the invitation of Federation ambassador Spock turn out to be a Romulan attempt to occupy Vulcan. While the scheme is thwarted by the crew of the Enterprise-D, Spock chooses to remain with the underground movement on Romulus. Later that year, the Enterprise assists a Romulan science ship, which has been unsuccessfully experimenting with a prototype interphase cloaking device that could represent a decisive tactical advantage for the Star Empire.
2369: The underground movement, assisted by Deanna Troi, manages to transport the defecting Vice-Proconsul M'ret and his aides to the Federation. Romulan forces also take part in the discovery of ancient humanoids, revealing the common ancenstry of Romulans and many other species of the Milky Way Galaxy. The Enterprise-D again assists a Romulan vessel, a warbird, which has been damaged by quantum singularity lifeforms and safely evacuates its crew before the warbird disappears.
2370: The Romulans learn of a violation of the Treaty of Algeron by Starfleet twelve years before, when a phasing cloaking device was illegally installed aboard the .
2371: Following first contact between the Dominion and the Alpha Quadrant, the Romulans consider the threat so severe that they plan to destroy Deep Space 9 and collapse the Bajoran wormhole, though their plan is discovered and abandoned. Simultaneously, the Romulans cooperate with the Federation by supplying a cloaking device for the , for use only in the Gamma Quadrant. In exchange, the Federation grants the Romulans access to all information gathered on the Dominion. Despite this cooperation, the Romulans attack the Amargosa observatory, searching for trilithium stolen from them by the Duras sisters. The Tal Shiar and the Cardassian Obsidian Order cooperate to launch a first strike against the Dominion but are decisively defeated at the Battle of the Omarion Nebula.
2372: The Antwerp Conference between the Romulans and the Federation takes place on Earth and is bombed by a Changeling infiltrator, killing twenty-seven attendees. Several Romulan outposts are attacked by the Klingons, as the Klingon Empire becomes increasingly aggressive following their invasion of the Cardassian Union.
2373: A Romulan fleet is dispatched to defend Deep Space 9, together with Klingon and Starfleet forces, against the Dominion and their new Cardassian allies, though battle does not occur. Later the same year, the Romulans sign a nonaggression pact with the Dominion.
2374: Romulans hijack the  but do not manage to bring the ship to Romulan territory. Following the death of Senator Vreenak, the Romulan Empire declares war against the Dominion and joins the Dominion War. The Romulans successfully fight alongside the Federation and the Klingon Empire in the First Battle of Chin'toka.
2375: The Romulans deploy plasma torpedoes on the Bajoran moon of Derna, but a Bajoran blockade and Federation pressure force them to withdraw from Derna. Kimara Cretak is expelled from the Romulan Senate as part of a Section 31 plot to bring Tal Shiar Chairman Koval into the Senate's Continuing Committee. Romulan forces are involved in the Federation Alliance-defeat in the Second Battle of Chin'toka. At the end of the Dominion War, Romulan forces participate in the victorious Battle of Cardassia, although their flagship is destroyed, and the Romulan Empire signs the Treaty of Bajor.
2379: A coup d'état kills almost the entire Senate and brings Shinzon into the position of praetor, who intends to use thalaron radiation to wipe out Earth's population and start a war with the Federation. He is ultimately defeated by the combined forces of the  and several Romulan ships, bringing the possibility of improved relations between the Romulans and the Federation.
2385: The Romulan government requests Federation assistance in evacuating Romulus due to the planet's impending destruction by a supernova. Using rogue synths, the Tal Shiar cabal Zhat Vash secretly orchestrates an attack on Mars that prompts the Federation to abandon its evacuation support and to ban artificial lifeforms.
2387: Despite Ambassador Spock's attempt to save the planet by creating a black hole, Romulus is destroyed by the Romulan sun going supernova, killing billions. Spock's vessel and a Romulan ship commanded by Nero travel through the black hole back in time, creating the alternate reality.
2399: By this year, a new political entity succeeding the Star Empire was the Romulan Free State, who controlled a a derelict Borg cube, which they exploited for technology amongst others. Romulan Zhat Vash operative Oh had infiltrated Starfleet and assumed the position of Chief of Starfleet Security by now, but is stopped in her attempt to destroy a colony of artifical lifeforms on Coppelius.
Post-24th Century: Romulan and Vulcan societies reunify, settling on Vulcan, re-named Ni'Var.

Appendices

Apocrypha 
The timeline of the video game Star Trek Online (shared in part with the Star Trek: Countdown) posits a different history for Romulan civilization, diverging at the death of Praetor Shinzon. The Romulan Star Empire fell into disarray due to Shinzon's assassination of the Romulan senate, verging on civil war between factions led by Tal'aura and Donatra, as well as attempts at secession by the Reman elements of the Star Empire.

Opportunistic expansion by the Klingon Empire into Romulan space further destabilized the Star Empire. Coupled with the destruction of the Romulan home system by supernova, the Empire fractured into multiple breakaway states. By 2408, Sela would claim power in the Star Empire, declaring herself 
empress. 

Another faction led by D'Tan a Romulan member of the Unification movement, relocated to the planet Dewa III, renaming it "New Romulus" and establishing the Romulan Republic. The Republic would come into conflict with the Star Empire through the Tal Shiar, but its democratic structure and proximity to newly discovered Iconian Gateways into the Delta Quadrant allowed it to form alliances with both the United Federation of Planets and Klingon Empire. The Republic, Federation, and Empire would eventually become the core founding members of a galactic alliance that would involve factions from all four quadrants.

See also
Interstellar history
Federation history
Vulcan history
Human history
Klingon history
Cardassian history

External link

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Romulus
History