Federation - Klingon War ( 2256 - 57 ) The Federation - Klingon War was a conflict fought between the United Federation of Planets and the Klingon Empire that began in 2256 with the Battle of the Binary Stars on stardate 1207 . 3 . This battle was provoked by T ' Kuvma , a Klingon from the House of T ' Kuvma , to rally the Empire to a common cause as he had portrayed the Federation as an existential threat , whose space had encroached unacceptably close upon that of the Klingons . In the first six months , the Federation lost 8 , 186 people . ( ) Captain of the claimed that sometime after the war began , he was given the freedom to do whatever it took to win the war , even if it meant breaking the rules of Starfleet . As part of this effort , Starfleet co - opted the research by Paul Stamets and Straal into an experimental spore drive . Six months into the war , the " Discovery " managed to practically implement the drive and went on to achieve a string of victories . This was made possible by capturing an alien it called a . ( ) In November of 2256 , a Klingon force managed to slip past the blockade defending Corvan II , a major resource hub whose mines produced forty percent of the dilithium supplies in the Federation . Without the planetoid , a sizable part of Starfleet would be grounded . By the time the colony managed to get out a distress call , the planetary defense shield s would only hold another six hours under the continued Klingon bombardment . With the closest ship much further away , the " Discovery " quickly responded , outmaneuvered , and destroyed the attacking Klingon vessels using its experimental spore drive . ( ) After their first success with the spore drive , " Discovery " quickly became the most important weapon in the Federation arsenal , causing the tide to turn and the Federation to start winning . In the three weeks following the relief of Corvan II , " Discovery " further used its drive to break the Klingon supply line at Benzar and rout an attack through the Ophiucus system . Starfleet started building spore drive units in a secret facility on Earth , while directing every ship , colony , and starbase to search for more tardigrade s . ( ) Around this time , General established a new ruling council . Starfleet believed that he had ousted the House of D ' Ghor and the House of Mo ' Kai , who secretly approached to discuss a potential alliance . However , this was in fact a ruse by Kol to capture a high - ranking Vulcan . The plan worked better than expected when , due to unforeseen circumstances , Admiral Katrina Cornwell arrived in the place of Sarek . After Cornwell ' s capture , Kol welcomed Dennas ' and Ujilli ' s Houses into his empire and promised them cloaking technology . ( ) By stardate 2136 . 8 , approximately ten thousand Starfleet personnel had been killed in the conflict . ( ) As more houses joined General Kol , the number of ships utilizing cloaking technology increased , and Klingon activity became more aggressive . A group of Klingon vessels utilized the new advantage to destroy a group of Starfleet vessels on patrol simultaneously , including the . Most disturbingly was that this advantage neutralized the tactics of the spore - equipped " Discovery " , which arrived to assist the " Gagarin " but could not save the stricken ship . ( ) Following the loss of the " Gagarin " , " Discovery " sought to use the natural crystal transmitter located on the planet Pahvo to locate cloaked Klingon vessels . However , their actions instead led the Pahvans to transmit a signal which attracted the attention of the Klingon flagship " Sarcophagus " . The crew of " Discovery " was able to board the Klingon ship and recover Admiral Cornwell from captivity , planting beacons to penetrate the cloaking field . Using the spore drive , " Discovery " was able to gather enough data to complete an algorithm which would counteract the cloaking technology , and then destroyed the Klingon ship . They intended to transmit this information to Starfleet , but did not get the chance . Attempting to use the spore drive to jump to Starbase 46 , the " Discovery " instead found itself in a parallel universe . Unbeknownst to Starfleet or the " Discovery " crew , the commanding officer , did this intentionally , trapping the ship and its crew . ( ) At the same time , the exchanged places with its counterpart , was attacked by Klingon forces , and was destroyed , leading Starfleet to believe that its " Discovery " had been lost . Without the cloak - penetrating algorithm , or the vital asset that " Discovery " had become , the Federation was unable to hold back the Klingon forces . In addition , having lost another unifying leader , the Klingons were no longer acting as a single force – instead , the twenty - four Houses competed for dominance by seeing which House could destroy the most Federation assets . The attacks were indiscriminate , targeting hospital s , civilians , and food convoy s . ( ) On stardate 4789 . 6 , hypothermic charge s were used against Kelfour VI , burning off the planet ' s atmosphere and instantly killing eleven thousand Federation civilians . Stardate 4851 . 5 saw the tailed by a cloaked Klingon raider as it arrived at Starbase 22 ; the raider then self - destruct ed , destroying the starbase . Similar attacks against Starbase 12 and Starbase 19 in the following days ultimately resulted in the loss of a third of the Federation fleet . Further assaults on the same stardate wiped out research outposts on Nivalla , Septra , and Iridin . ( ) Nine months after the destruction of the " Sarcophagus " , nearly twenty percent of former Federation space was occupied by the Klingons . At this point , " Discovery " returned to its own universe via the mycelial network , only arriving at that time due to having overshot their intended return trajectory . ( ) Although " Discovery " s return allowed the distribution of the algorithm , it was too late to prevent an assault on Starbase 1 by forces of House D ' Ghor , who eliminated the eighty thousand people aboard – including a significant part of Starfleet leadership – along with the three starships defending it . " Discovery " encountered the aftermath of the attack , with a House D ' Ghor sigil decorating the fallen base . With Klingon forces on the verge of striking Earth , and considering standard tactics to have failed , the Federation Council was forced to adopt a plan suggested by the stranded Terran emperor , . As a result , it authorized " Discovery " to use its spore drive to jump into the subterranean caverns of Qo ' noS in order to map the planet ' s defenses and infrastructure , ahead of an all - out assault on the planet , with the aim of forcing the Klingons to retreat from Federation space . The mirror Georgiou was disguised as her counterpart and placed in command of " Discovery " for the duration of the mission . ( ) The war concluded in 2257 when Georgiou planted a hydro bomb within a volcano on Qo ' noS . Preventing Georgiou from detonating the device , Burnham gave the detonator to L ' Rell , who used the threat of detonating the device to force the leaders of the Great Houses to accept her leadership role in the Empire . She ordered Klingon forces to halt their advance on the Federation , and then began working to continue T ' Kuvma ' s work of uniting the various Klingon factions . ( )