Borg - Species 8472 War The Borg - Species 8472 War was a brief , but highly destructive conflict fought between forces of the Borg Collective and Species 8472 . The war was fought over at least five months , ending in early 2374 . The war was triggered by Borg incursions into fluidic space – Species 8472 ' s native realm . However , Species 8472 ' s biological integrity proved highly resistant and up to being completely impervious to Borg technology . Species 8472 destroyed the invaders and proceeded to retaliate with an invasion of the Milky Way Galaxy , intending to purge it of what they considered inferior lifeforms . Species 8472 annihilated many Borg vessels and destroyed a number of their planet s . The Borg were on the verge of total defeat ; their invasion was repulsed only after Captain Kathryn Janeway of the provided the Borg with an effective weapon against them . ( ) Failed assimilation attempt . In late - 2373 , the Borg Collective learned of the existence of a species whose physiology they believed represented the " apex of biological evolution . " Designated Species 8472 by the Collective , this newly discovered race was the sole occupant of an extra - dimensional realm known as fluidic space . The Borg were determined to assimilate this species , which would bring them closer to their goal of perfection than any other species they had assimilated before . The Collective opened portals into fluidic space by creating special quantum singularities , using a modulated graviton beam . Borg vessels invaded fluidic space and attacked Species 8472 with the intent to forcibly draw the species into their fold , as they had done with thousands of other species before . However , when the Borg attempted to assimilate Species 8472 , they found that the species was immune to assimilation – their immune system was so efficient that any foreign body s encountered were immediately destroyed , including Borg nanoprobe s . Moreover , since the Borg learned about different species solely by means of assimilation , they were unable to understand or adapt to Species 8472 ' s technology . This organically - based technology was more than a match for Borg defenses . Species 8472 ' s vessels were nearly impervious to all types of conventional weaponry , while their weapons were able to penetrate Borg shields with ease . In short order , they eliminated the invaders . ( ) Purification . However , the sudden incursion of a hostile alien species in their biologically homogeneous space was intolerable to Species 8472 . They saw their realm as having been contaminated by weak lifeforms , originating from a galaxy full of similarly impure species that were intent on attempting to destroy them . Therefore , Species 8472 determined that the only course of action to protect their genetic integrity and prevent further attacks was to " purge " this galaxy of weakness – that is , destroy all life in it . Hundreds of their vessels began pouring into the Delta Quadrant , from a string of quantum singularities concentrated in a region of Borg space dubbed the Northwest Passage by the crew of the Federation starship USS " Voyager " . Species 8472 ' s purification campaign began with the extermination of the Borg Collective , as the Borg were the first species to contaminate their realm . ( ) The Borg found themselves at a disadvantage , because they gained knowledge through assimilation , which despite continued attempts remained futile . Even shortly before the end of the war , the Borg knew practically nothing about Species 8472 . Over the course of at least five months , Species 8472 attacked and swiftly defeated the Borg at least a dozen times . The area of space in which Species 8472 emerged , dubbed the Northwest Passage , was cleared of Borg activity . Two examples of their obvious combat superiority came shortly after " Voyager " s initial foray into Borg space . In one engagement , a single 8472 bio - ship annihilated an armada of fifteen vessels with ease . In a separate battle that occurred in Borg Matrix 010 , Grid 19 , the Borg lost 312 ships and 4 , 000 , 621 drones , and eight planet s were destroyed . By early 2374 , Borg tactical projections indicated that the war would be lost , and would be lost quickly . ( ) An infernal alliance . At that time , the USS " Voyager " was approaching the limits of Borg space and the Northwest Passage , intending to use the Passage , which had been detected as being devoid of Borg activity , to safely traverse Borg space . While just over a day away from the Passage , " Voyager " detected the remains of fifteen Borg cube s destroyed by Species 8472 , whom the " Voyager " crewmembers themselves had not yet encountered . Investigating , they discovered a single 8472 vessel among the debris . Hopes of finding a new ally against the Borg were quickly dashed after their first contact with the pilot : " Voyager " barely managed to escape , and their operations officer , Ensign Harry Kim , was almost killed . During the brief exchange , Kes , " Voyager " s Ocampa medical assistant , was telepathically contacted by the aliens , resulting in the " Voyager " crew learning of their plans . Captain Janeway realized that the Borg were no longer the main threat ; Species 8472 posed a far greater threat than the Borg had ever done . Ironically , the Borg , the Federation ' s greatest enemy , were the best chance of stopping the invasion . In a daring move , Janeway decided she would forge an alliance with the Borg ; she would offer them a weapon against Species 8472 , in exchange for " Voyager " s safe passage through Borg space . Janeway ' s bargaining chip was The Doctor , who had discovered a way to reprogram Borg nanoprobe s to avoid detection as foreign bodies by Species 8472 ' s immune system . These reprogrammed nanoprobes would then be able to attack Species 8472 cells , unlike regular nanoprobes . Janeway ordered " Voyager " into System D43119 , an assimilated star system , and began negotiations with the Collective , intending to offer The Doctor ' s research as tactical data about its enemy , in exchange for safe passage of " Voyager " through Borg territory . She had all of the data put into The Doctor ' s holomatrix ; she would have him deleted , and the data along with him , if the Borg tried to assimilate " Voyager " . An agreement was reached ; the Borg would escort " Voyager " through their space , and , while " en route " , " Voyager " personnel would assist the Borg in crafting the research into a biological weapon . The first test of the alliance came when a Species 8472 fleet attacked the system during the negotiation . A planet in the system was destroyed , but a cube escaped , using its tractor beam to tow " Voyager " out of danger along with it . ( ) In the next several days , Captain Janeway and Lieutenant Tuvok , her chief tactical officer , worked with the Borg drone Seven of Nine , selected by the Collective to act as its representative to make communication between the two groups easier . They developed a method of introducing the nanoprobes via photon torpedo es , essentially converting them into bio - molecular warhead s . However , Species 8472 exploited their telepathic connection with Kes to locate the two ships , and learned of the nanoprobes . An 8472 vessel attacked , and the Collective sacrificed the cube to save " Voyager " , but not before beaming Seven of Nine and a small contingent of drones aboard " Voyager " to continue the work . Janeway was severely injured in the attack , and Commander Chakotay , her first officer , decided to dissolve the alliance rather than rendezvous with another Borg cube . The weapon . Running out of time , the Collective decided to force Chakotay ' s hand by taking " Voyager " into fluidic space . Seven of Nine commandeered the ship ' s navigational deflector and used it to open a quantum singularity , through which " Voyager " was pulled into Species 8472 ' s realm . During this attempt , Chakotay ordered Seven of Nine to stop or he would eject the drones into space ; however , after carrying out his threat , Seven of Nine survived . Faced with an imminent attack by Species 8472 , Janeway , now recovered from her injuries , allowed Seven of Nine to modify " Voyager " to fire the bio - molecular warheads after relieving Chakotay of duty . The weapon proved effective , as all four 8472 vessels attacked were destroyed . The goal completed , Seven of Nine took " Voyager " back out of fluidic space , after which it destroyed thirteen more 8472 vessels with a high - yield warhead armed with the nanoprobes . Seven of Nine transferred the specifications of the weapon to the Collective . The demonstration had the desired effect : alarmed at their new - found vulnerability , Species 8472 fell into full retreat on all fronts and began disappearing back into fluidic space . ( ) Aftermath . Once the invasion had been repelled , the Borg promptly terminated the alliance with " Voyager " and attempted to assimilate the ship and crew through Seven of Nine . The attempt failed , however , due to advanced planning by Captain Janeway and Chakotay . Chakotay possessed a residual link to a mini - collective of former Borg drones he had encountered , months before . ( ) He used it to link with Seven of Nine to distract the drone while the chief engineer , Lieutenant B ' Elanna Torres , sent a power surge through the link , permanently severing Seven of Nine from the hive mind . Cut off from the Collective , Seven of Nine gradually regained her individuality and Humanity . Most of her Borg implants were removed and she became a valued member of the " Voyager " crew . ( ) Over the course of the next few months , " Voyager " encountered at least one member of Species 8472 still in their galaxy . It was being chased by a Hirogen hunting vessel . After both the remaining member of Species 8472 and an Alpha - Hirogen battled on " Voyager " , Seven beamed the two back onto the hunting vessel . ( ) Due to the defeat of Species 8472 , the Borg were able to continue on their path of assimilation , and some , such as Arturis of Species 116 , blamed " Voyager " s intervention in the war and tried to take revenge for the events . ( ) On the up side , the defeat of Species 8472 averted an invasion of the Milky Way which could have cost every single life inhabiting the Milky Way galaxy , although " Voyager " s crucial role in the conflict caused Species 8472 to begin preparations for an invasion of the Federation . It was not until over a year after the war ended , when " Voyager " established diplomatic contact with Species 8472 , that these plans were reconsidered . ( )