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The Borg Invasion of 2381 was the historic attempt by the Borg Collective to completely exterminate the United Federation of Planets, the Klingon Empire, and other allied worlds in the Alpha and Beta Quadrants and to subjugate the remaining worlds in local space. It ended with the Collective being dismantled and subsequently absorbed into the Caeliar gestalt.

The invasion left dozens of worlds in the area of the Azure Nebula in utter ruin, decimating much of known space. As a result of the invasion, upwards of 40% of the Federation Starfleet was destroyed, and over 63 billion citizens of the United Federation of Planets, the Klingon Empire, the Romulan Star Empire, the Imperial Romulan State, and non-aligned worlds were killed. (ST - Destiny novel: Lost Souls)


Towards the end of the year 2377, the USS Voyager under the command of Captain Kathryn Janeway, with the aid of Admiral Kathryn Janeway from the future, destroyed the Borg Collective's Transwarp Hub and also infected Unimatrix One with a virus that killed the Borg Queen and severely damaged the Unicomplex. As a result, the entire Borg Collective came to regard the Federation as a threat that could no longer be tolerated.

  • Note: The Borg incursions shown in TNG novels: Resistance, Before Dishonor, Greater Than the Sum were not said to be precursors of the invasion, despite both incidents occurring before Borg invasion. In this case, all attacks were by Borg drones that had been out of contact with the larger collective mind and attacked independently.

Opening attacks[]

In January of 2381, one month after Captain Picard and the crew of the USS Enterprise-E destroyed the Borg-assimilated Einstein, the Collective launched surprise attacks on the worlds of Barolia and Acamar III, completely eradicating their populations. The Borg then sent an ominous message to the Federation: "We are the Borg. You will be annihilated. Your biological and technological distinctiveness have become irrelevant. Resistance is futile... but welcome."

Over the next five weeks, there were three more Borg attacks, and Starfleet had yet to discover how the Borg were so easily slipping past their defenses. Ezri Dax, recently-made captain of the USS Aventine, proposed to Starfleet that there may be some connection between the Borg attacks in the Alpha Quadrant and the discovery of the 22nd century Starfleet vessel Columbia in the Gamma Quadrant seven years earlier. With no other leads to follow, Captain Dax and the Aventine were dispatched to the Gamma Quadrant to resume the investigation into the Columbia's mysterious appearance there.

Weeks passed and Starfleet's losses against the Borg continued to mount. A Borg cube attacked the world of Ramatis III. The Enterprise destroyed the cube with transphasic torpedoes, but was unable to save the planet's population. Captain Picard later argued that every ship in the fleet should be armed with the transphasic torpedoes, but Admiral Alynna Nechayev overruled him, saying that overusing the torpedoes would allow the Borg to adapt faster.

Shortly after the destruction of Ramitis III, the Borg launched simultaneous attacks on Korvat, Khitomer, and Starbases 234, 157, and 343. The Enterprise managed to stop the Borg attack on Korvat, saving 29,000 people (out of an original population of 10 million). At Khitomer, the USS Ranger sacrificed itself to protect the Klingon colony. The USS Excalibur successfully repelled the Borg at Starbase 343. Starbases 234 and 157 were both destroyed, however. Amongst the casualties was Admiral Owen Paris, who was stationed at Starbase 234 at the time of the attack. A short time later, the Borg attacked and destroyed Starbase 24.

Back on Earth, Federation President Nanietta Bacco made plans to call for all the powers in the Alpha and Beta Quadrants to unite against the Borg. At the same time, she enlisted the aid of the former Borg Drone Seven of Nine to assist Starfleet in planning a defense. On Qo'noS, Chancellor Martok called upon the Klingon High Council to aide the Federation against the Borg, citing the sacrifice of the Ranger at Khitomer. Meanwhile, the Aventine was recalled from the Gamma Quadrant.

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Borg Cubes about to assimilate a world.

The Azure Nebula[]

After analyzing the wreckage of the Borg cube destroyed over Korvat, Geordi La Forge theorized that the Borg were originating from the Azure Nebula. The Enterprise set course for the Nebula. There, they found three Borg cubes waiting for them. In the battle that followed, the Enterprise destroyed two of the cubes, but was damaged herself. Fortunately, the Aventine appeared via a subspace tunnel and assisted the Enterprise in destroying the third cube.

After the battle, Captain Dax revealed to Picard the existence of the subspace tunnels inside the Azure Nebula. One of these tunnels had been responsible for sending the Columbia into the Gamma Quadrant 200 years earlier. Picard and Dax deduced that the Borg in the Delta Quadrant were using a similar tunnel to launch their attacks on the Federation. Initially, Picard and Dax planned to set up a minefield - similar to the one used to mine the Bajoran wormhole during the Dominion War - while they came up with a way to collapse the tunnels. However, it was discovered that the apertures from the tunnels would make that impossible. Furthermore, they could not close the tunnels without doing severe damage to the rest of the galaxy. Admiral Nechayev ordered the Enterprise and the Aventine to scout the tunnels and find out which one the Borg were using so that Starfleet could set up a blockade on the other side until they could safely collapse the tunnels.

Back on Earth, Seven of Nine attempted to convince Starfleet Command that they should use the subspace tunnels to evacuate the Alpha Quadrant and escape the Borg. Her suggestion was instantly rejected, as was her suggestion about building a Thalaron generator to use against the Borg. Meanwhile, President Nanietta Bacco succeeded in gaining the support of the Klingon Empire, the Romulan Star Empire, the Imperial Romulan State, the Cardassian Union, the Ferengi Alliance, the Breen Confederacy, the Talarian Republic, the Gorn Hegemony and the Orions.

An allied fleet of over three hundred allied ships assembled at the Azure Nebula in preparation to blockade the Borg's staging ground. However, while the Enterprise and the Aventine were away investigating one of the tunnels, a massive Borg armada of 7461 vessels came through another tunnel and attacked the allied fleet. Almost the entire allied fleet was destroyed, with only a handful of surviving ships, including the USS Voyager. The Borg armada dispersed into Federation, Klingon, and Romulan space and began their final assault.

The Invasion[]

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Federation starships engaging a Borg cube.

The worlds of Beta Thoridor, Adelphous IV, and Devnar IV were the first to fall. Yridia, Hyralan, Celes were also attacked and destroyed. Starfleet was unable to organize any sort of defense against the overwhelming number of Borg ships. Worse, the Federation did not have enough ships to evacuate the endangered worlds. Seven of Nine attempted to locate the Borg Queen's ship, but was unable to isolate it. Out of desperation, Admiral Jellico distributed the schematics for the transphasic torpedo to all Federation and Klingon ships, despite knowing the risk that they might fall into the hands of the Borg.

The Klingons, now armed with transphasic torpedoes, managed to successfully defend the planet Morska from the Borg. Khitomer and Rura Penthe, however, were destroyed (though no one cared about Rura Penthe). Chancellor Martok rallied the Klingon fleet to stop the Borg before they reached Qo'noS. Despite their valiant defense, many Borg ships broke through the Klingon lines and headed straight for the Klingon home world. Meanwhile, the Borg attacked and destroyed the Federation world of Deneva, killing its entire population. The Borg then proceeded to attack more worlds including Regulus, Elas, Troyius, Ajilon, Archanis, Castor and Risa.

Back at the Azure Nebula, the starships Enterprise and Aventine returned from the Delta Quadrant after a bloody encounter with a pack of Hirogen Hunters. After learning about the invasion, Dax wanted to chase after the Borg, but Picard convinced her not to act hastily. Instead, the two captains contacted Starfleet for orders. Starfleet, however, had no orders to give them. The President gave Picard authority to do whatever it took to stop the Borg. Admiral Jellico privately told Picard that if Earth was destroyed, he should take what survivors he could and leave.

The Enterprise was then unexpectedly contacted by the USS Titan under the command of Picard's friend and former first officer, William T. Riker. The Titan had just escaped from their captivity by the Caeliar, and had brought back with them a surprise guest: Erika Hernandez - the former captain of the NX-02 Columbia, long thought to be dead. Hernandez had been a virtual prisoner of the Caeliar for over 800 years, but had been persuaded to help the Titan escape when she learned that Earth was in danger. Her body had been modified with Caeliar Catoms which had kept her virtually immortal for the last 800 years. To everyone's surprise, these Catoms also allowed her to tap into the Borg Collective.

Acting on this information, Dax came up with an audacious plan to board a Borg ship and "plug" Hernandez into its Vinculum. Hernandez could then use her Catoms to pose as the Borg Queen and take control of the invasion force. Picard disagreed with this plan, considering it too risky, but Dax decided to proceed anyway. After locating a lone Borg probe, Dax used the Aventine's quantum slipstream drive to ambush the probe and disable it. Security teams then boarded the probe, and the Aventine set up a series of dampening fields to disable the Borg Drones' weaponry and the ship's internal defenses. The Starfleet boarders used TR-116 projectile rifles and chemical explosives to kill the Drones. Despite taking heavy casualties from both the Borg and friendly fire, the security teams prevailed and secured the probe.

Hernandez interfaced with the probe's Vinculum just as the Borg began their attacks on Qo'noS, Vulcan, Andor, Coridan, and Beta Rigel. Posing as the Queen, she took control of the armada and forced the Borg to fight each other. In doing so, not only were Qo'noS, Vulcan, Andor, Coridan, and Beta Rigel saved from destruction, but nearly half of the invasion force was destroyed. Unfortunately, the real Queen regained control and ordered her remaining forces to regenerate. She then launched a psychic attack against Hernandez, nearly killing her. The Queen also personally took control of the probe and used its own architectural structure to attack the Starfleet personnel. The Starfleet teams, however, managed to escape back to the Aventine. The probe was then destroyed by a bomb the boarders had planted.

Starfleet's victory, however, was short-lived. Despite having lost nearly half their ships, the Borg armada quickly resumed its advance into Federation territory. Worse, the Borg had now fully adapted to the transphasic torpedo. The Federation was now truly defenseless. Knowing nothing could stop the Borg from reaching Earth now, President Bacco gave the order for all ships in Sector 001 to disperse.

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Borg drone boarding party on Federation starship.

Arrival of the Caeliar[]

When Captain Hernandez returned to the Aventine, she made a startling revelation to Dax: While linked to the Vinculum, she had discovered uncanny similarities between the Borg Collective and the Caeliar gestalt. She came to the conclusion that the Borg were in fact the result of a botched fusion between the Caeliar and human crewmen from the Columbia. With this knowledge, Dax and Hernandez presented a new plan to Picard: Contact the Caeliar and enlist their aid in dismantling the Collective. Once again, Picard refused, for fear of the Borg assimilating the Caeliar's powerful technology, but Riker managed to convince him that this was their best (and only) option left.

With the Enterprise's help, Hernandez contacted the Caeliar and showed them what she had learned about the Borg. After some debate, she convinced them to bring their city ship Axion to the Alpha Quadrant. She also agreed to return to the Caeliar in exchange for the release of the Titan personnel currently being held aboard the Axion (amongst them were Deanna Troi and Tuvok). The Axion traveled to the Azure Nebula, where it rendezvoused with the Enterprise, Aventine, and Titan. The Borg armada, which was mere seconds away from attacking Earth, detected the Caeliar's Omega molecule generator. Driven to assimilate the Omega molecule, the Borg Queen ordered the entire invasion force to head for the Azure Nebula.

The end of the Borg[]

The Caeliar opened up hundreds of subspace tunnels and brought the entire Borg armada to the Azure Nebula. Hernandez then enacted her plan. She transported herself aboard the Queen's ship and allowed the Queen's drones to attack and inject her with Nanoprobes. Her Catoms clashed with the Borg Nanoprobes, allowing the Caeliar gestalt to use her as a conduit to wage a psychic battle against the Collective. The Caeliar gradually overpowered the Collective and gained access to the Queen herself. They then discovered the true power behind the Borg to be the lost Caeliar Sedín, who had degenerated into an entity of pure hunger and rage. The Caeliar subdued Sedin and extracted her from the minds of her victims, dissolving the Collective in the process.

Though the Collective was gone, trillions of Drones were still mentally linked to each other. Leaderless and confused, they began to go insane. With the Caeliar's help, however, Hernandez extended the power of the gestalt to every Drone through out the galaxy, transforming their Borg implants and Nanoprobes into Caeliar Catoms. In doing so, the former Drones' individuality were restored while their mental link to each other was maintained, allowing them to join the Caeliar gestalt. The crews of the Enterprise, Aventine, and Titan all watched in amazement as the Borg armada was transformed into a fleet of silver sea urchin-like spheres. Hernandez then contacted the Enterprise and informed Picard, Riker, and Dax that all the Borg in the galaxy had been transformed into Caeliar and that the Caeliar would now leave to take care of their new children. The Axion and the transformed armada then vanished to parts unknown.


The Borg invasion had enormous repercussions for the Alpha Quadrant. Sixty-three billion people were killed and billions more were left homeless. Forty percent of Starfleet was also destroyed, leaving the Federation in a weakened state. As of 2382, a year after the invasion, the Federation was still dealing with the fallout of the invasion - most notably the rise of the Typhon Pact.

The demise of the Borg led to a new front in the Temporal Cold War, as all the factions fighting were from futures where the Borg were defeated - it was noted by Federation Temporal Agent Jena Noi that in almost every possible history where the Borg were not defeated in the 24th century they assimilated the entire galaxy by 2600. Thus the factions considered it too dangerous to attack the Federation before the Borg's defeat. (DTI novel: Watching the Clock)

In the months following the invasion, two initiatives were launched by the Federation council. The first, the Luna-class starship program was to continue and push on as the flagships of the Federation exploration arm, with the USS Titan leading all exploratory efforts as the flagship of the exploration corps. (TNG novel: Losing the Peace)

The second initiative involved a revision of the mission orders for the Project Full Circle fleet to return to the Delta Quadrant and try to locate any remaining Caeliar or Borg technologies. (VOY novel: Unworthy)

Known locations attacked by the Borg[]


Known casualties of note[]

Known ships destroyed[]



Alternate realities[]

In an alternate 2409, these events had never occurred, sparing many of the casualties of the war such as Admirals Kathryn Janeway and Owen Paris. Agent Marion Dulmur of the Department of Temporal Investigations of that timeline, however, remembered the events of the Borg invasion, along with various events from differing timelines, such as the destruction of Vulcan in the Kelvin timeline. (STO novel: The Needs of the Many)

Cryptic Studios was in Alpha testing for Star Trek Online during 2008 when Star Trek: Destiny series detailing the Borg Invasion was first released. While there are other differences between the two continuities in the preceding time period, Destiny is the major point of divergence and most subsequent events happen quite differently (e.g. the Typhon Pact never forms).



Major Borg attacks on the Federation
Borg emblem icon image. 2366-2367 IncursionBattle of Sector 0012376 Invasion2377 InvasionSupercube Crisis2381 InvasionFrontier Day 2401 takeover2409 Invasion2411 Invasion Borg emblem icon image.

References and notes[]