Time Wars

The Time Wars were an ancient era of Gallifreyan history marked by numerous conflicts wherein the Time Lords ensured their supremacy, eradicating all other lifeforms with the potential for time travel. (PROSE: Sky Pirates!, The Gallifrey Chronicles, Heart of TARDIS) The Time Wars lasted for 30,000 years on 1000 planets, becoming a "nightmare of contradiction, paradox, and death." (PROSE: The Infinity Doctors) Entire future species and whole orders of species were destroyed; Time Lords of this era successfully fought against the Charon, (PROSE: Sky Pirates!) Great Vampires, Narlok, Racnoss, (PROSE: River of Time) Order of the Black Sun, (COMIC: 4-D War, PROSE: Heart of TARDIS) Vondrax, (AUDIO: Enemy Lines) and countless other "nameless races" of which no record survived. (PROSE: Sky Pirates!, River of Time) Additionally, many parallel Gallifreys were erased from existence. (PROSE: The Infinity Doctors)

Campaigns of the Time Wars period included the Black Sun War, (COMIC: 4-D War, PROSE: Heart of TARDIS) the Eternal War, the Racnoss Wars, (PROSE: River of Time, et al.) the Millennium War, (PROSE: The Quantum Archangel) and the Great Inferno. (COMIC: Terrorformer)

Ultimately, the Time Wars ended in Time Lord victory. These conflicts helped to stabilise reality, laying the foundations for the rationalistic universe of the Doctor's era. (PROSE: The Infinity Doctors) Artifacts of the Time Wars remained strewn across history, (PROSE: Sky Pirates!, River of Time, Damaged Goods, AUDIO: The Scent of Blood) as well as many lone survivors of races targeted by the Time Lords in this time. (PROSE: Sky Pirates!, The Gallifrey Chronicles, River of Time, TV: State of Decay, The Runaway Bride, COMIC: Terrorformer)

The Time Wars
The Doctor once claimed the Time Wars were fought a generation or so after Rassilon, (PROSE: The Infinity Doctors) but the Time Wars era included even Rassilon's founding of Time Lord civilisation. The Fourth Doctor mentioned that Rassilon discovered the secrets of time by stealing the translation belt of a species who attacked Gallifrey in the Time Wars "in retaliation for things we did to them before we'd even heard of them in the first place." (PROSE: Heart of TARDIS) Such an event occurred during Omega's fall, when Fenris—sent from 30,000 years in the future—sabotaged the initial Gallifreyan time travel experiments at Qqaba and caused Omega's apparent death. Rassilon prevented further damage and dispatched Fenris, finding that Fenris' discarded belt provided much-needed technology to harness time travel. (COMIC: Star Death) It would not be until 30 years later that the next generation of Time Lords—such as Rema-Du, the daughter of two Elders of Gallifrey present at Omega's fall—would fully understand the motivation of Fenris' employers, the Rigel sector's Order of the Black Sun. The time war fought against the Order was the Black Sun War. (COMIC: 4-D War, Black Sun Rising)

Some accounts place the Eternal War against the Great Vampires as beginning or continuing into the early era of the Time Lords, (PROSE: The Multi-Faceted War, The Book of the War) having lasted over a thousand years. (PROSE: The Pit) The Eighth Doctor, when telling James Macfarlane of the Vampire War, mentioned that it was just one of many wars fought by the Time Lords at the time. (AUDIO: The Scent of Blood) Atraxi was the sole Gallifreyan warrior to return from the Eternal War; he tried to warn the now-scientific Time Lords that the War would continue and they weren't safe from "the Monsters", but quickly died from Rassilon's plague. (PROSE: The Pit)

Gallifrey of this early era was characterised by such stimuli as "the stink of steaming grease from the first breeding engines, the marching chants of the first parahuman brigades, and the songs of the killer cats in the south." (PROSE: Hark! The Herald Angels Sing) One parahuman mercenary group, the Special Executive, had significant involvement in the Black Sun War. (COMIC: 4-D War, Black Sun Rising)

The Time Wars began concurrently with the Rutan-Sontaran War. (PROSE: The Infinity Doctors) The Sontaran Brilox was involved in instigating the Black Sun War on Desrault. (COMIC: Black Sun Rising)

Those species which Gallifrey could not conquer became allied with the Time Lords in their wars. (PROSE: A Brief History of Time Lords) The Qwerm were among those who joined the Time Lords in fighting the Great Vampires, Racnoss, and "whatever other races wanted to sweep across the universe like a plague". (PROSE: River of Time)

The Fourth Doctor told Wblk that he had been at the Time Wars as an eyewitness. (PROSE: Heart of TARDIS) The Fifth Doctor later became involved in the Racnoss Wars. (AUDIO: Empire of the Racnoss)

The Ra'ra'vis captured Rassilon while he was on a military trip and tried to force him into giving them time travel. Rassilon was rescued by Vogans. (PROSE: Jorus and the Voganauts)

Gallifrey developed a planet-sized warship armed with the Cold, but ultimately never got the chance to use it. (PROSE: The Infinity Doctors, Interference)

Once the Time Lords achieved victory in their initial wars, they realised that they had caused the permanent militarisation of those species they allied with, creating "a new generation of problems" to be eradicated. The Qwerm hid before they could be destroyed by the Time Lords. (PROSE: River of Time)

The Order of the Black Sun existed thirty-thousand years after Omega's death, (COMIC: Star Death) at the end of the Time Wars. (PROSE: The Infinity Doctors)

Ultimately, after thirty-thousand years of conflicts, "certain higher powers" stepped in to stop the devastation before it destroyed the universe. (PROSE: The Infinity Doctors)

Aftermath
The title "Time Wars" was retroactively applied to this era of Gallifreyan history. (PROSE: Sky Pirates!) Time was stabilised after the Time Wars, but the Time Lords were forced to seal off whole areas of time and space which were damaged beyond repair. (PROSE: The Infinity Doctors)

One reality bomb remained drifting in the Horsehead Nebula for fifty billion years before catching the Seventh Doctor's TARDIS. (PROSE: Sky Pirates!)

By the era of Ulysses, Mister Saldaamir was considered the last survivor of the Time Wars. (PROSE: The Gallifrey Chronicles)

By some point, the Time Lords co-existed as Higher Evolutionaries alongside other powerful time-aware factions, (COMIC: The Tides of Time) even the Order of the Black Sun. (COMIC: The Final Chapter)

Wblk claimed the Time Wars didn't happen. (PROSE: Heart of TARDIS)

During the War in Heaven, Time Lords revived and augmented ancient biological defenses created during previous time wars against threats such as the Charon and the Great Vampires. (PROSE: The Ancestor Cell)

Behind the scenes

 * Lance Parkin submitted an entry for The Book of the War, later published in the fan magazine Myth Makers, which included further information on the Time Wars as they pertained to Mister Saldaamir. Saldaamir's home planet was "unhappened" in the Time Wars and he lost his memory, family, friends, and companions. He survived by rooting himself to a new location by hastily marrying a passing witch, similarly to how the Eighth Doctor survives the unhappening of Gallifrey by rooting himself to Earth through marrying Scarlette in PROSE: The Adventuress of Henrietta Street.
 * The Time Wars are described in Jacob Black's My Best Enemy..., published in the charity anthology Unbound: Adventures in Time and Space, as involving "Rassilon's specially woven armies of crusaders" and having been over in an instant. The Lords of Althrace are posited as having only survived the Wars due to Rassilon requiring the harmonic effects of their Event Synthesizer.