(covers information from several alternate timelines)
The Battle of the Binary Stars, also referred to as the Battle of the Binaries, was the opening battle in the Federation-Klingon War between the United Federation of Planets and the Klingon Empire. The battle took place in 2256, on stardate 1207.3. (DIS: "Context Is for Kings", "Choose Your Pain")
The Battle of the Binary Stars was the first time the Federation and Klingons had engaged each other since the Battle of Donatu V in 2245. Prior to the battle, the two powers had barely interacted with each other – barring a few inconclusive skirmishes such as at Donatu V and Doctari Alpha – in a full century. (DIS: "The Vulcan Hello", "Battle at the Binary Stars")
The Klingon leader T'Kuvma ordered his ship, the Sarcophagus, to disable an interstellar relay on the edge of Federation space, in an uninhabited binary star system six light years from Gamma Hydra. He wanted to disable the relay in order to lure a Starfleet vessel to investigate, so he could provoke a confrontation. The USS Shenzhou responded, and, on investigation, Commander Michael Burnham was attacked by the Klingon Rejac but killed him in self-defense.
Upon her recovery, the Shenzhou sent out distress calls to any nearby Starfleet vessels to warn them of the Klingon incursion into Federation space. Meanwhile, T'Kuvma activated the Beacon of Kahless to call on the twenty-four Klingon Great Houses to unify and send their own ships to aid him. Soon, twenty-four ships dropped out of warp, one from each of the Great Houses, but while the Klingons were debating whether or not to unify into a single fleet, ten Starfleet ships, responding to the distress call, dropped out of warp behind the Shenzhou. Both newly arrived fleets then faced each other down in a tense confrontation. (DIS: "Battle at the Binary Stars")
The battle began after T'Kuvma ordered his ship to open fire on the Shenzhou, forcing it to take evasive maneuvers and fire in retaliation. To cover the Shenzhou, the starship USS Sioux, along with others, moved up and opened fire, inflicting considerable damage to the smaller Klingon ships. However, Starfleet began to take considerable losses early on in the battle, with the USS Clarke and USS Yeager destroyed, and the Shenzhou heavily damaged and unable to fight. (DIS: "Battle at the Binary Stars")
At this point, the Shenzhou began drifting toward the debris field and was left by the Klingons to be destroyed by a collision with a large asteroid. Moments from impact, the USS Europa arrived at the battle and saved the Shenzhou with a tractor beam. (DIS: "Battle at the Binary Stars")
Following this, Admiral Brett Anderson made contact with the Klingons and managed to negotiate a brief cease fire. But, while communicating with Captain Philippa Georgiou on the Shenzhou, the Europa was deliberately rammed by a cloaked Klingon cleave ship. The low-speed collision began tearing through the Europa's saucer section, ripping it apart like paper. With this happening, the Europa deliberately collapsed its anti-matter containment field, which overloaded the warp core. The resulting breach destroyed both vessels. The cease fire was broken, the Klingons resumed shooting, and a wave of new Klingon reinforcements warped into the system as well. Several other Starfleet vessels were destroyed, until only the Klingons remained. T'Kuvma told the other Klingon leaders that they should return home and declare far and wide that the Klingons fought as a united empire again, and they departed – but T'Kuvma stayed behind on his flagship, the Sarcophagus, to recover their fallen comrades for proper funeral rites. (DIS: "Battle at the Binary Stars")
As the Klingons collected their dead, the crew of the Shenzhou transported an explosive photon torpedo warhead onto the body of a Klingon warrior adrift in space. As the body was tractored into the Klingon flagship, it detonated, severing the "head" of the ship, and inflicting considerable damage. Captain Georgiou and Commander Burnham took this opportunity to board the ship in order to take T'Kuvma prisoner. While searching the ship, the officers were ambushed, and a brief fight ensued. Commander Burnham was knocked down but was able to overcome her attacker. However, Captain Georgiou was stabbed through the chest by T'Kuvma and killed. Burnham then shot T'Kuvma in the back, killing him. She was then beamed back before she could recover Captain Georgiou's body, and the Shenzhou was abandoned. (DIS: "Battle at the Binary Stars")
Ultimately, the battle was a massacre for the Federation, with thousands killed and a number of ships destroyed. The Klingons also took Lieutenant Ash Tyler prisoner and kept him aboard a prison ship. (DIS: "Into the Forest I Go", "Battle at the Binary Stars") While the Klingons also took casualties, T'Kuvma achieved his goal: using a war against the Federation to reunite the Great Houses. However, with T'Kuvma dead, the Klingons were left without a living leader, and T'Kuvma's vessel and its surviving crew, as well as the only extant Klingon cloaking device, were left to drift for months in the debris field of the battle. Kol, of the House of Kor, managed to take command of the Sarcophagus, however, after he bribed the remaining crew to follow him instead of T'Kuvma's protégé Voq, and then to abandon Voq aboard the derelict Shenzhou. (DIS: "The Vulcan Hello", "Battle at the Binary Stars", "The Butcher's Knife Cares Not for the Lamb's Cry", "Choose Your Pain")
After that, L'Rell had Voq taken to the Matriarchs of the House of Mo'Kai, where he underwent surgery to pose as Ash Tyler in order to infiltrate Starfleet. Kol later became a general and consolidated his power over the Klingon High Council. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry", "Choose Your Pain", "Lethe", "The Wolf Inside")
In the mirror universe, Captain Michael Burnham made a name for herself as "the Butcher of the Binary Stars" after directing an Imperial assault in the system. According to Voq, she killed thousands of Klingons with a single command. (DIS: "The Wolf Inside")
|Battles of the Federation-Klingon War (2256-57)|
|2256: Battle of the Binary Stars • Attack on Corvan II • Battle at Pahvo|
|2257: Scorching of Kelfour VI • Attack on Starbase 22 • Attack on Starbase 12 • Attack on Starbase 19 • Attack on Nivalla • Attack on Septra • Attack on Iridin • Capture of Starbase 1|
AT: "Into the Forest I Go" erroneously referred to this conflict as the "Battle at the Binary Stars", though it is canonically called "Battle of the Binary Stars" (in "Context Is for Kings", "Into the Forest I Go" and "Despite Yourself") and "Battle of the Binaries" (in "Choose Your Pain").
While the USS Shenzhou was being designed, it was intended that the fleet of Starfleet ships in this battle would deliberately be in the shapes of various discarded Shenzhou design concepts. Recalled concept illustrator John Eaves, "I talked it over with Todd Cherniawsky, who was the production designer by that point, and we eventually came up with the theory to explain why these new ships didn't have round nacelles and looked a bit out of place." Eaves and Cherniawsky conceived of the ships in the fleet as being similar to experimental X-planes from actual history, which had radically varying configurations even though they were all designed for the same purpose. The pair of designers conceived of this experimental phase as the result of a scenario they imagined, in which the Humans in Starfleet had decided they no longer wanted the Vulcans to be influential on matters of ship design. (Star Trek: Discovery Designing Starships, pp. 47, 55, 58)
The novel Dead Endless depicts a parallel universe where Michael Burnham decided to trust her captain instead of firing on the Klingons. As a result, the Battle of the Binary Stars and the subsequent Federation-Klingon War never happened. The incident was instead called the Standoff at the Binary Stars.