The Earth-Romulan War, also known as the Romulan War, was a major interstellar conflict fought from 2156 to 2160 between the forces of United Earth and those of the Romulan Star Empire. Its conclusion, which was marked by an Earth/Andorian/Vulcan/Tellarite alliance decisively defeating the Romulans at the Battle of Cheron, led to the establishment of the Romulan Neutral Zone and immediately preceded the incorporation of the United Federation of Planets. (ENT: "In a Mirror, Darkly, Part II"; TOS: "Balance of Terror")
In the early 2150s, Earth began to make impressive diplomatic and military advancements in the Alpha Quadrant. Major conflict between the Vulcans, Andorians, and Tellarites had for the most part ended thanks to diplomatic intervention by United Earth and the starship Enterprise, under the command of Captain Jonathan Archer. The Romulans saw this newfound peace in the region unacceptable, and thus began a carefully crafted campaign to destabilize the region and maintain the status quo of conflict between the quadrant's major powers.
At some point prior to 2154, a reunification movement began to become popular among some Romulan and Vulcan citizens. In that year, the Vulcan High Command, under the leadership of Administrator V'Las, planned to launch a preemptive strike against Andoria, citing that the Andorians were developing weaponry based on Xindi technology. Additionally, the Earth embassy on Vulcan was bombed prior to the attempted execution of these plans, prompting involvement by United Earth and Starfleet. Although V'Las's plans were halted and his involvement with the bombing was exposed, his connection with a Romulan operative who had been working on Vulcan with V'Las for several years remained secret. (ENT: "The Forge", "Awakening", "Kir'Shara")
Later that year, the Romulans attempted to incite a war between Andoria and Tellar by using automated drone ships to attack Andorian and Tellarite targets. Unfortunately for the Romulans, this had the opposite effect of what they were hoping to achieve; instead of destabilizing and dividing the region, the attacks resulted in a successful allied effort to stop the drone ships and return peace to the region. (ENT: "Babel One", "United", "The Aenar")
In early 2155, the consolidation of interests among Earth and some of its neighbors reached a new milestone, when a conference to form a Coalition of Planets was convened. It included participants from the later war allies and Federation founders, i.e., Vulcan, Andoria, and Tellar, in addition to United Earth. (ENT: "Terra Prime", "Demons")
In 2266, Spock categorized the weaponry generally used in the Earth-Romulan War as atomic in nature, and fairly primitive at that. He also characterized the ships in use as primitive, and designed in ways that did not permit quarter or captives.
Romulan starships were painted to resemble a "bird of prey", a tradition kept through the mid-23rd century. Ship-to-ship visual communication between Earth-allied ships and Romulan-allied ships did not take place during the war or during the peace negotiations.
Among the casualties during the course of the war included several members of the Stiles family, including one Captain Stiles, two commanders and several junior officers. (TOS: "Balance of Terror") A number of MACOs also fought in the war, including Balthazar Edison. (Star Trek Beyond)
The Battle of Cheron in 2160 is generally considered the decisive battle that marked the end of the Earth-Romulan War. Both sides recognized the major victory achieved here by a Human/Vulcan/Andorian/Tellarite alliance as a humiliating defeat of the Romulan military. This event established long-term political effects within the Romulan Empire that went on to last well into the 24th century. (ENT: "In a Mirror, Darkly, Part II"; TNG: "The Defector")
Despite the Romulan's 2154 campaign of destabilization and the war that followed, Earth and Romulus learned little of each other in the 22nd century. In fact, it would be over a century before any Human would even see what a Romulan looked like. (TOS: "Balance of Terror")
Following the Battle of Cheron, the two sides negotiated a treaty via subspace radio. Among other things, it established a neutral zone, entry into which by either side would constitute an act of war. Earth set up at least eight outpost stations on asteroids along its side of the Neutral Zone to monitor Romulan activity.
From a 23rd-century Human perspective, the Neutral Zone represented an area "between planets Romulus and Remus and the rest of the galaxy." Some Humans still harbored resentment over the war after over a century of peace, including Lieutenant Stiles of the USS Enterprise.
Despite these Human attitudes, until 2266 the Neutral Zone served its purpose and the treaty had remained unbroken. In fact, one might say it served its purpose too well, as there were limited or no contacts between Earth and the Romulan Star Empire from the conclusion of the war until the mid-23rd century. (TOS: "Balance of Terror")
During the Dominion War, two centuries later, Captain Benjamin Sisko alluded to this war when he warned the Federation President Jaresh-Inyo of "the thought of a Jem'Hadar army landing on Earth without opposition." Adding that, "They don't care about the conventions of war or protecting civilians. They will not limit themselves to military targets. They'll be waging the kind of war that Earth hasn't seen since the founding of the Federation." (DS9: "Paradise Lost")
|Earth wars prior to the Federation|
|Crusades • American Revolution • American Civil War • World War I • World War II • Brush Wars • Earth Cold War • Eugenics Wars • World War III • Earth-Kzin Wars • Xindi incident • Earth-Romulan War|
The details of the Earth-Romulan War have remained canonically vague. As Spock said about the war, "As you recall from your histories, this conflict was fought, by our standards today, with primitive atomic weapons and in primitive space vessels which allowed no quarter, no captives. Nor was there even ship-to-ship, visual communication; therefore, no Human, Romulan, or ally has ever seen the other. Earth believes the Romulans to be warlike, cruel, treacherous... and only the Romulans know what they think of Earth." The exact dates for the war and several details above are derived from a viewscreen graphic seen in the Star Trek: Enterprise episode "In a Mirror, Darkly, Part II". The graphic was comprised of data points from an outdated version of the Star Trek Chronology.
Prior to this, a behind-the-scenes newspaper clipping titled It's Federation Day!, which was among the collection found in the Picard family album from Star Trek Generations, dated "11 Oct. 2161", stated that the war ended "a little more than a year" prior to the final declaration of peace and the foundation of the Federation. This source also stated that the war ended with the Battle of Cheron in early 2160. This information did not appear on screen.
Some evidence indicates that Earth itself commenced the conflict, as Data remarked in "The Defector" that "in their long history of war, the Romulans have rarely attacked first…. They prefer to test their enemy's resolve." In other words, Earth may have been provoked into acting first, either intentionally or possibly inadvertently. However, it may have been one of the few occasions on which the Romulans did attack first, such as the events that transpired in "Balance of Terror".
The fourth season of Star Trek: Enterprise began to show the very early beginning of the coming conflict with the Romulans. Writing couple Judith and Garfield Reeves-Stevens kept what had and hadn't been established about the war in mind during the writing of the Babel Crisis trilogy of episodes (namely, "Babel One", "United", and "The Aenar"), including the fan expectation that the Federation had been formed in the aftermath of the conflict. In fact, while the trilogy was in development, very little had been confirmed about the timing of the war. Recalling the little evidence available from canon, Garfield Reeves-Stevens commented, "All we know is that the Romulan Wars occurred about the same time the Federation occurred in – we know the year the Federation occurred in but we don't know what year the Romulan War occurred in or how long it lasted. We know it was fought and we know they never met each other. So we typed up memos with these key points that everyone should keep in mind in developing stories, and one conversation we had was that in the original series it was never called the Romulan Wars, it was called the Romulan Conflict, and everyone was concerned with how you could have a war where the antagonists never meet. We came up with the idea that what if it was a phony war and the Romulans were sending out robotic ships." These concepts never made it into established canon but did influence the trilogy and inspired the invention of the Romulan drone ships. (Cinefantastique, Vol. 37, No. 2, pp. 39-40)
Had Enterprise been renewed for a fifth season, it would have continued to show the whispers of the Romulan War and eventually allow the conflict to be realized on screen. Additionally, according to rumors at the time, Rick Berman and Brannon Braga considered making "Future Guy" a Romulan. However, this was simply a "red herring": Braga intended "Future Guy" to be a future version of Jonathan Archer.  
An early concept for a proposed eleventh Star Trek film – Star Trek: The Beginning – would have revealed the beginnings of the Earth-Romulan War. However, this concept, which included Romulan drone ships in the conflict, was scrapped for the film Star Trek.
In the Star Trek Star Fleet Technical Manual, Franz Joseph offered a one-page version of the subspace peace treaty that concluded the war. It was signed by "Christofur Thorpe" for Earth and "Praetor Karzan" for the Romulans.
There are several points of ambiguity involved with this time period. For more information on those topics, please see cloaking device, Romulan Bird-of-Prey (22nd century), and Romulan Bird-of-Prey (23rd century).
Spaceflight Chronology (1979)
In the reference book Spaceflight Chronology, more detailed accounts are given of the events that led to the war and the war itself. Fourteen years prior to the actual war, the Romulan Star Empire began a campaign of attacks disguised as random space pirate activity. The first of these attacks was the hijacking of the ore freighter USS Muleskinner. Two years later, the Delta VII outpost was attacked. Five years after this, the commercial transport Diana was attacked with its cargo stolen and crew killed. Four years prior to the actual war, the reports on piracy attacks were, for the first time, perceived as possibly being organized. Three years before the war, Starbase 1, in Sector 3A, was destroyed by what was still believed to be an act of space piracy. Romulans were, for the first time, identified as the culprits. All transports were given military escorts at this time. Two years before the war, the Romulan threat became apparent. A year before the war, Romulans made a number of hit-and-run attacks on several sectors.
The actual war began when a full Romulan invasion fleet, advancing on the Rigel system, was encountered by the destroyer USS Patton. In the second year of the war, Romulans managed to destroy a mining complex in Sector 5B. A Romulan armada was completely destroyed in Sector 7. In the third year of the war, Romulans attacked Alpha Omega. Victory in the war was credited to advanced ship-mounted laser weaponry, developed only two years before the war as a response to the destruction of Starbase 1. The dates of these events in the timeline of the Spaceflight Chronology differ from the canonical timeline. Also, the major difference between these accounts and canonical accounts is that the war is stated to have been fought by the Federation, not the allied forces as was established later on in the viewscreen graphic from "In a Mirror, Darkly, Part II".
Federation - The First 150 Years (2012)
According to the reference book Star Trek: Federation - The First 150 Years, Praetor Gileus led the Romulan Star Empire into the war against United Earth by ordering a surprise attack on Starbase 1, on Algeron. During the conflict, Denobula tried to remain neutral, but in 2158 a Romulan fleet attacked the planet in order to use one of its orbital space stations as staging ground for an attack on the Sol system; fortunately for Earth, Starfleet assumed as much and was able to prepare defenses, turning the eventual assault into a Midway-esque catastrophe from which the Romulans would never recover. Although this occupation only lasted a short time, three million Denobulans were killed by orbital strikes, causing them to be more skeptical and to not join the Federation immediately, in 2161.
The Battle of Cheron was ultimately won by Earth when the starship Lexington, combined with a small fleet of Denobulan ships, set a course for Romulus. Gileus, fearing that the impending attack would threaten his power, prematurely ordered his fleet defending Cheron to return to Romulus mid-battle, allowing Enterprise and Atlantis to destroy the shipyards there. Shortly afterwards, the Romulans sued for peace, and the Neutral Zone was established.
The Pocket ENT "relaunch" arc by Michael A. Martin, which is consistent with the Star Trek: Destiny series of novels by David Mack, covers the events from the end of Enterprise to the Romulan War. It starts with Trip Tucker faking his death so he can spy on the Romulans, who are attempting to create a warp-seven capable ship. This reinterprets the events shown in "These Are the Voyages...", moving them to 2155. According to the series, the Romulans started the war out of fear of the birth of the Coalition of Planets, by attacking proposed member Coridanite (thus delaying their entrance into the alliance until The Original Series) and then by attacking a number of Coalition ships using a telecapture device and destroying the Kobayashi Maru as seen in the novel Kobayashi Maru. The novel series Star Trek: Enterprise - The Romulan War details the war proper. According to the novel Last Full Measure as well as the older novel Starfleet: Year One, the Federation was born as a result of the conflict.
In DC Comics' The Mirror Universe Saga, the Earth-Romulan War marks the point of divergence for the mirror universe; in the mirror universe, Earth lost the war, was occupied by the Romulans, and the resistance that eventually fought them off took control of the planet and proclaimed that Humanity would now be the conquerors, not the conquered. This was later on established not to be the case in the Star Trek: Enterprise episodes "In a Mirror, Darkly" and "In a Mirror, Darkly, Part II", that establish that, if there was a divergence point, it was somewhere before the 16th century.
According to the 2006 game Star Trek: Legacy, a Vulcan scientist named T'Uerell supplied the Romulan Star Empire with metagenic weapons to use against Earth colonies. Earth used the radiation from nuclear reactors in the Tyburn system to halt a large Romulan force from reaching Earth – explaining the use of atomic weapons. The Last Unicorn Games book Among the Clans: The Andorians makes reference to a series of Earth-Romulan wars, taking place during roughly the same time as the single canonical war.
Diane Duane's 1987 novel The Romulan Way, published fourteen years before Star Trek: Enterprise aired, gives an entirely different version of events. In this version, the Romulans were still a pre-warp people when the Federation discovered them. The Romulans mistook the exploration vessel for a precursor to invasion and quickly created a fleet of primitive, sublight warships which they used to capture the next Federation ship to approach Romulus. From it, they reverse-engineered a number of technologies, including warp drive. Things escalated from there, and the Federation eventually negotiated the Treaty of Alpha Trianguli entirely by subspace radio, setting up the terms of the Romulan Neutral Zone and designating a swathe of space surrounding the Romulan system as the Romulan Star Empire.