The Battle at Federation Headquarters was a conflict fought between the United Federation of Planets and the Emerald Chain in 3189, after forced peace negotiations between the Federation and the Chain broke down.
Prelude[]
A few days before the battle, the USS Discovery was on assignment at the Verubin Nebula, investigating a Federation distress call coming from somewhere within the nebula. While there, the ship and its crew were attacked and captured by Osyraa. Her ship, the Viridian, latched onto Discovery, and used the ship's Spore Drive to jump them both back to Federation Headquarters.
Once there, Osyraa opened forced negotiations with the Federation, however, she broke up the talks when Admiral Charles Vance said the only way the Federation would accept the alliance was if Osyraa faced justice for her crimes. Osyraa refused and returned to Discovery, where she discovered that the senior staff, thanks to the Andorian Ryn disabling the sensors, were attempting to retake control of Discovery. She demanded Ryn to restore the sensors. Ryn refused and Ossyra killed him. She then ordered the Viridian to open fire on Federation Headquarters so they could escape.
The battle[]
As Discovery attempted to escape the shield of Federation Headquarters, Admiral Vance ordered the USS Voyager-J to take the lead on Viridian, while the rest of the fleet inside the shield targeted the Discovery. Aboard Discovery, Osyraa orders her regulators to fire on the complex's primary shield emitter, which is disguised as a secondary deflector array. Lt. Audrey Willa tells Vance the emitter will last less than five minutes against the barrage and Vance orders the fleet to hit Discovery harder.
As Discovery leaves the shield perimeter, A regulator reports that Discovery's crew has engaged in a firefight on Deck 7. Osyraa orders all regulators to evacuate to Deck 5 or above immediately.
On Deck 7, Sylvia Tilly, Gen Rhys, Joann Owosekun, Keyla Detmer, R.A. Bryce, Lt. Ina and DOT-23 drones controlled by the Sphere data trade fire with the regulators, who retreat to the upper decks per Osyraa's instructions. The computer reports life support is being shut off and atmosphere drained.
The complex's shields start to fail, allowing the Viridian to provide cover fire for Discovery to escape. A surprised Lt. Teemo reports that a Ni'Var fleet is about to arrive to provide backup. The Ni'Var Razors are blocking Discovery's path out, so Osyraa directs the Viridian to deploy its cache of pesticides, targeting shuttlebays, airlocks and other intakes. Before that can occur, Michael Burnham contacts Vance, asking him to stand down. However, Discovery is still pursued by the Federation and Ni'Var fleets.
In engineering, Tilly and the other officers are having difficulty breathing and are sharing among them one oxygen mask. Owosekun explains that she has superior lung capacity having grown up free-diving for abalone in the Ogbunike Caves. Bryce reports he cannot bypass the Emerald Chain's command functions. A hard reboot could restore computer systems, but they would have to access the data core. Burnham and Booker, grounded by the transporter jammer, sneak through the ship, avoiding regulators. Burnham has a plan, but tells Booker it will "make Sigma X feel like a vacation." Using one of the regulator's badges, Burnham broadcasts an audio message across the ship: "It wasn't a particularly happy birthday. But I found you. We played seven-card stud and drank synthehol. Too bad we didn't have fireworks. Nothing stops a party like fireworks." Tilly explains to the others that on her birthday the year prior, she was going "through a hard time" and hid in a nacelle after her shift. Burnham found and distracted her until midnight, never mentioning Tilly's birthday. Tilly realizes Burnham's message was directing her to use an incendiary device to destabilize the superconductors holding the now-detached nacelle in place, knocking the ship out of warp and allowing the pursuing fleets to catch up.
Owosekun arrives at the nacelle access point having run out of supplemental oxygen and barely able to stand. She places the bomb but, weak, collapses before leaving. One of the DOT-23 drones controlled by the Sphere data arrives, urging her to stand. It reaches out for her just as the bomb explodes. The nacelle now destabilized, Discovery is forced out of warp. Discovery reenters normal space, careening wildly off its axis. The turbulence knocks Burnham and Booker, as well as their respective assailants, to the ground. The Viridian surrounds Discovery inside a large internal chamber to protect from the pursuing force.
In the data core, Osyraa and Burnham engage in hand-to-hand combat, and Osyraa manages to force Burnham into a wall made of programmable matter. Burnham says they do not have to be enemies, but Osyraa responds that trying to negotiate with Vance was a mistake. She pushes Burnham backwards into the wall, which subsumes her. Osyraa looks on satisfied, but a few moments later Burnham shoots her dead from inside the wall before emerging and coughing up some of the matter. "Yeah, well, unlike you, I never quit," she says to the dead Osyraa. Burnham performs a hard restart of the computer systems, restoring the Starfleet programs. Having regained control, she restores life support on all decks, beams the regulators off Discovery and diverts auxiliary power to shields. On a shipwide channel, she orders any crew who can hear her to report to the bridge.
On the bridge, Michael proposes a plan to overload and eject the ship's warp core and jump from inside the Viridian using Booker to control the Spore Drive. They enact the plan, and Discovery manages to jump away seconds before the warp core detonated, destroying the Viridian from the inside.
Aftermath[]
After regaining control of their ship, Discovery successfully returns to Federation Headquarters. For her actions in recovering the ship, Michael is promoted to Captain, and takes command of Discovery.
Without Minister Osyraa's command, the Emerald Chain fractures, and is no longer a threat to the Federation.
President T'Rina returns to Federation Headquarters to officially open a dialog to rejoin the Federation.