War

A war was a type of conflict, typically initiated by a declaration of war. Scales of war included civil war, space war, interplanetary war, interstellar war, and time war.

Overview
According to the Kaled military officer Major Brogan, "War [did] terrible things to good people", by bringing out extremes in emotion and behaviour. (AUDIO: Innocence) The Fifth Doctor believed that "war can make monsters of the best of us". (AUDIO: Empire of the Racnoss)

Though the goal of a war was victory over the other side, (TV: The Armageddon Factor, AUDIO: Purity) the Thirteenth Doctor held that "no one ever wins at war". (PROSE: The Good Doctor)

War was an expensive venture, (TV: The Armageddon Factor) and it had its victims. (AUDIO: Purity)

The Twelfth Doctor stated wars, after massive casualties and destruction, always ended with people doing what they should have done from the beginning, which was to "sit down and talk". (TV: The Zygon Inversion)

"When you fire that first shot, no matter how right you feel, you have no idea who's going to die! You don't know whose children are going to scream and burn. How many hearts will be broken! How many lives shattered! How much blood will spill until everybody does what they were always going to have to do from the very beginning: Sit down and talk!"

- Twelfth Doctor

Braxiatel believed that all wars, at heart, were incredibly banal. (AUDIO: Enemy Lines)

Article 15 of the Shadow Proclamation said that murder was not a rule of war. (PROSE: Diamond Dogs)

The Third Doctor warned a Thal expedition working against the Daleks not to glorify their stories upon their return to Skaro, to avoid the prospect of war sound exciting to the largely peaceful race. (TV: Planet of the Daleks) He also acknowledged, however, "the sad truth" that war often bred progress, and that without any such dynamic, many species and civilisations risked remaining static. (PROSE: Catastrophea) held a similar belief, opining that if "necessity is the mother of invention, then war is its father." (AUDIO: The Destination Wars)

Toshiko Sato observed that "everything wage[d] war", that it was a trait not just of humanity but of existence. (TV: Greeks Bearing Gifts)

The Ninth Doctor told Rose Tyler that the Nestene invasion was not a price war. (TV: Rose)

Conflicts
The Time Lords warred with the Great Vampires during the Dark Times. (TV: State of Decay) They also engaged in two major time wars which appeared to destroy Gallifrey: the War in Heaven against the enemy, (PROSE: Alien Bodies, The Ancestor Cell) and the Last Great Time War against the Daleks. (TV: Dalek, The Day of the Doctor) The latter conflict was viewed by General Staal as the "finest war in history", bitterly recalling that the Sontarans were excluded from it. (TV: The Sontaran Stratagem) By this point in Gallifreyan history, the Doctor was recognised as the "saviour of Gallifrey in the war with the Vardans". (PROSE: Dalek Combat Training Manual) According to the Seventh Corsair, the Destruction of Skaro by the Hand of Omega triggered a "little" time war, which was eventually erased by the Time War. (PROSE: One Virtue, and a Thousand Crimes)

Ultimately, the Last Great Time War ended with Gallifrey and the Time Lords being shunted into a parallel pocket universe. When the Time Lords attempted to leave this realm, it caused the Siege of Trenzalore with the various races of the universe fearing a second time war. Through a force field established by the Papal Mainframe, the Eleventh Doctor enforced an uneasy truce. (TV: The Time of the Doctor) Viewing this situation as an "endless, bitter war", (TV: A Good Man Goes to War) the Kovarian Chapter attempted to prevent the Doctor from reaching Trenzalore but ultimately ended up ensuring that he would. When the New Dalek Paradigm conquered the Church, the Siege turned into an open war, one that lasted centuries. (TV: The Time of the Doctor) In the Unbound Universe, the Time Lords fought in the Great War, ultimately perishing in the fighting. (AUDIO: Asking for a Friend)

Earth had at least six world wars: Two in the 20th century, (TV: Twice Upon a Time, PROSE: Timewyrm: Exodus) two between the 20th and 25th centuries, (AUDIO: Frostfire) one in the 37th century (COMIC: Art Attack) or the 49th century (AUDIO: Singularity) and one in the year 5000. (TV: The Talons of Weng-Chiang; AUDIO: The Butcher of Brisbane) The Ninth Doctor mentioned he was present at World War V. (TV: The Unquiet Dead)

Rose Tyler remembered the Battle of Canary Wharf in 2007, in which humanity endured conflicting invasions by both the Cybermen of a parallel universe and the Cult of Skaro, as a war. (TV: Army of Ghosts/Doomsday)

In the early 26th century, the expanding empires of Earth and Draconia clashed in the Human-Draconian War, ending in an uneasy peace which and the Daleks failed to break. (TV: Frontier in Space)

As described by the Eleventh Doctor, the Daleks perpetually waged war against the rest of the universe and "all lifeforms that are not Dalek". (TV: Victory of the Daleks) After the First Doctor helped defeat the Daleks during the First Dalek War, his granddaughter Susan stayed on Earth with resistance fighter David Campbell. (TV: The Dalek Invasion of Earth, Prelude Deceit) In the centuries that followed, the Dalek Empire waged a further series of wars, labelled as the Dalek Wars, against the galaxy. (PROSE: The Whoniverse) The Second Dalek War began in 2540 after the Daleks failed to reignite the Human-Draconian War. (TV: Frontier in Space) A Third Dalek War broke out in its aftermath. (PROSE: The Chase, Deceit) The Daleks faced numerous powers in the Great War waged over the millennium following the year 4000. This conflict ended when the Second Doctor used the Human Factor to create a number of Humanised Daleks who rejected the Dalek Emperor, resulting in a Dalek Civil War breaking out on Skaro. (PROSE: The Evil of the Daleks)

The Daleks also warred against the Mechanoid Empire, (COMIC: Impasse) and fought against the Movellans. (TV: Destiny of the Daleks) The Dalek Empire eventually collapsed into the civil war between Davros' Imperial Daleks and the Dalek Prime's Renegade Daleks, causing the Daleks to begin losing their campaigns against alien forces. (AUDIO: Innocence) Eventually reuniting the Dalek Empire fought and died in the Last Great Time War against the Time Lords. (TV: Dalek) At its onset, the New Dalek Paradigm sought to wage war on many rival empires but was consistently foiled in its efforts by the Eleventh Doctor. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) They fought humanity, defended by the Space Security Service, in a war in the 41st century, (COMIC: The Only Good Dalek) as well as sending Survey Ships into Earth history to observe how humans waged war in what was designated the Dalek Project. (COMIC: The Dalek Project) When Oswin Oswald deleted all information about the Doctor from the Pathweb, the Paradigm's war efforts ground to halt as they attempted to make sense of their memories. When they regained their memories of the Doctor via turning Tasha Lem into a Dalek puppet, the Paradigm declared war on the Doctor at the Siege of Trenzalore. Historians who succeeded the conflict believed, though were not certain, that the Paradigm had devoted the entirety of its army to this war and that their defeat had been the final fall of the Daleks. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) The Final Dalek War was a hypothesised future conflict, supposedly sparked by Skaro's penultimate destruction. Gordel theorised that the Needle People were the super-evolved survivors of the Thal race, fleeing the Final Dalek War. (PROSE: The Infinity Doctors)

The War Lords kidnapped humans from various wars in Earth's history to create an army to conquer the galaxy. (TV: The War Games)

The Rutans and Sontarans were at war with each other for thousands of years. (TV: The Time Warrior, The Sontaran Experiment, Horror of Fang Rock, The Poison Sky)

Just prior to invasion of Earth by the New Dalek Empire in 2009, General Sanchez, director of UNIT's base in New York City, announced "ladies and gentlemen, we are at war!" The Shadow Architect, having determined that the stolen planets were taken with hostile intent, had the Shadow Proclamation declare war "right across the universe". The Tenth Doctor, however, refused to lead them into battle as he headed to the Medusa Cascade without them. (TV: The Stolen Earth)

In the face of an attack on the Game Station by the Daleks in the year 200,100, Jack Harkness announced "this is it, ladies and gentlemen, we're at war!" (TV: The Parting of the Ways)

Throughout the history of the universe, the Cyber-Wars were a series of conflicts where the Cybermen sought to upgrade all of humanity. (TV: Nightmare in Silver) In the 22nd century, the Vogans of Voga fought the CyberNomads in what became known as the Vogan War. (PROSE: Killing Ground) The Great Cyber War, (AUDIO: Last of the Cybermen) also known as the Second Cyberwar, (PROSE: Original Sin) ended in a human victory over the Cybermen through the creation and use of glitterguns, (AUDIO: Last of the Cybermen, TV: Revenge of the Cybermen, et al.) The Cybermen were a key player in the Orion War after this. (AUDIO: Scorpius) By the 33rd century, historians referred to the "Great Orion Cyber Wars" of the 26th century. (WC: Real Time) The Third Cyberwar saw the Cybermen face an expanding Human Empire. (COMIC: The Scruffy Piper) The Cyber Wars of the 250th Millennium, (PROSE: The Secret Lives of Monsters) fought between the Cybermen and humanity, ended with the destruction of the Tiberian Spiral, though the remnants of the Cybermen later resurfaced. (TV: Nightmare in Silver) The last known of these conflicts saw the fall of the Cyber-Empire and the near extinction of both humanity and the Cybermen. (TV: Ascension of the Cybermen) In the far future, "fake Cyberdudes" liked to reenact battles from the Last Great Cyberwar. (COMIC: Vortex Butterflies)

Other references
Brother Lassar of the Krillitanes asked the Tenth Doctor if he would declare war on them. (TV: School Reunion)

Brock of the Shoal of the Winter Harmony took the Twelfth Doctor's opposition to them as a declaration of war. The Doctor maintained that he was "drawing a line", going on to suggest that they "step back from it with awesome speed". (TV: The Return of Doctor Mysterio)