War Doctor

The "War Doctor", also known as "the Renegade", was the incarnation of The Doctor who fought in Last Great Time War and in that war saw the most direct combat. He stemmed from the regeneration of the Eighth Doctor and regenerated into the Ninth Doctor. Originally young and robust, he disowned the name of the Doctor, feeling unworthy of it. After becoming old and tired of battle and faced with the end of reality, this Doctor considered activating the Moment, to commit genocide against both the Daleks and his own people. (TV: The Night of the Doctor, COMIC: Sky Jacks) Though his later incarnations disowned him, believing him to have burned Gallifrey, he in fact did not, but the memory of saving the planet was lost when his time stream wasn't in sync. Thus, the Ninth and Tenth Doctors and, for much of his life, the Eleventh Doctor, still believed the War Doctor was responsible for Gallifrey's fall, despite having a pivotal role in rescuing the planet. (TV: The Day of the Doctor)

Born for the battle
After the Eighth Doctor crash-landed during the Last Great Time War, he was revived temporarily by the Sisterhood of Karn, who offered him the ability to control his regeneration and become the person he needed to be to end the Time War. Initially he refused, but after witnessing the death of Cass (the starship's pilot, who refused the Doctor's help because he was a Time Lord) he accepted their help and asked them to make him a warrior. After drinking the Elixir of Life, he regenerated into his new incarnation, who promptly rejected the name of the Doctor, declaring, "Doctor no more". (TV: The Night of the Doctor)

During the Last Great Time War
The War Doctor was present at the fall of Arcadia, where he used a high-tech gun to inscribe the words "no more" onto a wall as a message to the Time Lords and the Daleks. He then destroyed a group of Daleks with his Tardis, before fleeing the planet.

At the end of the war, he fled to a desolate wasteland, where he intended to trigger "The Moment," a weapon of ultimate destruction which would have completely wiped out the Time Lords and the Daleks. The Moment, however was sentient, and possessed a conscience. Its interface manifested into the form of his future assistant Rose Tyler to challenge his use of the weapon. (TV: The Day of the Doctor)

Meeting with the future Doctors
Upon realising that the the War Doctor was planning on using it, the Moment appeared to him, creating a time fissure that would send him into his own personal future where he met with the Tenth and Eleventh Doctors in 1562 England, in order to witness the effects that making such a choice would have. The War Doctor realised the Moment didn't show him "any old future", but exactly the future he needed to see. Queen Elizabeth I placed the three Doctors in a dungeon in the Tower of London. She left the door open to see what sort of plan they would make. The War Doctor placed the calculation to disintegrate the structure of the prison door as a permanent subroutine in the sonic screwdriver. 400 years later, by his eleventh incarnation, the sonic, in a different case but using the same software, completed the calculation. Before they could do anything, Clara Oswald opened the unlocked door, freeing them.

Elizabeth I showed the Doctors that the Zygons were placing themselves inside stasis cubes so that they would awaken when Earth became a more interesting place to invade. Realising the Black Archive, which the Zygons had taken over in Earth's future, was impenetrable from the TARDIS, the Eleventh Doctor told McGillop to place the stasis cube, Gallifrey Falls No More, inside the Archive before the Zygon attack. The three Doctors put themselves inside the cube, where in the 21st century they would awaken and stop the Zygons.

The Doctors wiped the minds of Kate Stewart, Osgood and McGillop as well as the Zygons impersonating them starting peace talks, cancelling the detonation nuclear weapon beneath the Archive and beginning peace talks between the humans and Zygons, as neither side knew which was the fake and which was real. The War Doctor felt that the regret the Eleventh Doctor felt following his decision at the end of the Time War would have led to the saving of many more worlds and decided to activate the Moment. The Tenth and Eleventh Doctor joined him to press the button, but before they did, Clara insisted them to think of something else, which they did.

The Eleventh Doctor cancelled the Moment's detonation, and all thirteen of the Doctor's incarnations, using calculations starting from the beginning of his life, safely placed Gallifrey in stasis in a pocket universe using their TARDISes as the Daleks focused their gunfire, using the same principle as that of the stasis cube. The disappearance of Gallifrey caused the Daleks to be caught in the crossfire. The War Doctor realised that it would have appeared to the rest of the universe that they annihilated one another, as Gallifrey was gone and the Daleks were destroyed. Because the Doctors' time streams were out of sync, the War Doctor didn't remember their effort to save Gallifrey, rather than burn it, and realised he would have to live with that. (TV: The Day of the Doctor)

Death
After growing remarkably old and grizzled, the War Doctor had not discovered how frail his body had turned, focusing nearly all his attention on the Time War. By the time he had parted ways with the Tenth and Eleventh Doctors and entered his TARDIS, his regeneration was triggered automatically. He chuckled at the sight of his old body renewing itself, happy that the tribulation of the Time War was coming to an end. Much like his first life, he commented that this body had worn thin. Perfectly content, he joked, "I'd hope the ears are a bit less conspicuous this time". He gladly allowed his regeneration to pass and changed into his next incarnation. This new incarnation lost the crucial memories of how the Time War truly ended, believing his people were lost forever. (TV: The Day of the Doctor)

Undated adventures

 * The War Doctor, though not using the title of "Doctor" anymore, attended the funeral of Alistair Gordon Lethbridge-Stewart, as did all of his other incarnations. (PROSE: The Gift)

Legacy
The Sontarans told legends of the Doctor leading Time Lords into battle. (TV: The Sontaran Stratagem) Likewise, opposing Daleks were frightened of his presence in the Time War and began to call him "The Oncoming Storm", a title that began in his eighth incarnation but fully rose to prominence when he at last showed them no mercy. (PROSE: Vampire Science, TV: The Parting of the Ways)

The Tenth Doctor told the Cult of Skaro that he survived the Time War "by fighting, on the front line", mentioning the fall of Arcadia as one of the battles he was present at. (TV: Doomsday)

His supposed actions tormented many future lives of the Doctor, who were haunted for centuries on end by the dual genocide he remembered orchestrating. After his days in this incarnation were over, the Doctor decided to forget this entire life; he would never be acknowledged again, and became his greatest secret, one he would take to the grave. (TV: The Name of the Doctor) Despite his attempts to forget, the Doctor occasionally thought about his secret incarnation in addition to his other eleven lives, even though he did not like to think about it. (PROSE: Nothing O'Clock)

The Eleventh Doctor, upon coming into contact with this incarnation, spurned the very memory of him. He went so far as to suggest this incarnation did not even hold the moniker of "the Doctor" due to his actions in life. He explained to Clara that his real name was not the point; he chose the name "the Doctor" and explained that the name a person chose was like a promise. This unknown incarnation was "the one who broke the promise". He described him as "my secret". This ninth incarnation responded by defending those actions, stating that what he did, he did "without choice" and "in the name of peace and sanity". The Eleventh Doctor acknowledged that as true, but rebutted that it had not been "in the name of the Doctor". As he carried Clara away, the War Doctor turned around and watched them with a sombre stare. (TV: The Name of the Doctor) When the Eleventh Doctor entered into the T'keyn Nexus (similar to the Matrix on Gallifrey) in order to defend himself, all 12 of his incarnations appeared inside it to defend himself. Although the War Doctor was there with the others, he was the only one not to defend his name. Instead, the Eighth Doctor had to defend what the War Doctor had (supposedly) done in the Time War and all he did to avoid it. (COMIC: Dead Man's Hand)

Ultimately, the Doctor remembered the true result of the Time War, and after reassessing the War Doctor, declared that this incarnation "had been the Doctor more than anyone else". He forgave the past actions of his previous life and moved on, proudly remembering the valiant actions the War Doctor took instead, and used them as an example to live by once again as he began the search for Gallifrey, wherever the Doctors had sent it. (TV: The Day of the Doctor)

Personality
The War Doctor was also stern, as indicated by his dislike for childlike vocabulary like "timey-wimey". He considered the fact that the Eleventh Doctor used such words as a proof that he is ashamed of being a grown-up.

The Time War caused the War Doctor to be addled with much regret, sadness, and weighted guilt, but he also managed to be cheerful and compassionate with a few hints of witty humour and sarcasm, indicating he was not inherently evil like the other incarnations were led to believe. Though not as quicksilver as his younger able-bodied selves, his older age allowed him to pace his thinking and not jump to conclusions that the flighty Tenth Doctor would, sometimes seeing a hidden solution after much contemplation. Upon learning that he had a chance to rights the wrongs of his life, he became quite elated and took solace in restoring his right to be called the Doctor. Once the Time War had come to a close, he had lived a full life and held no qualms about regenerating into another body, facing the end with an immense grin in his last moments. (TV: The Day of the Doctor)

When questioned by his future incarnation on the actions that he had to make during the war, the War Doctor responded by defending those actions, stating he had "no choice" and that he did what he did "in the name of peace and sanity." (TV: The Name of the Doctor)

Despite his experiences, he could be an appealing and gentle figure. He was also something of a gentleman, judging by his reaction to Clara Oswald and despite a bumpy start he ended up getting on rather well with the Tenth and Eleventh Doctors. (TV: The Day of the Doctor)

Appearance
This incarnation originally had a stern, shaven and determined face with a head of dusty brown hair. (TV: The Night of the Doctor) However, after spending an inordinately long period fighting in the Time War, he became jaded and tired, with pronounced wrinkles and weary eyes. However, Clara noticed these eyes were younger than those of his future lives in that they were more hopeful. His hair colour turned entirely to a deep silver, which he slicked up in peaks at the top of his head. The elderly War Doctor also allowed himself to grow a full beard; he was the only incarnation to normally sport facial hair, rather than go clean-shaven, further distancing him from the other lives of the Time Lord. (TV: The Name of the Doctor)

The War Doctor appeared old and bedraggled, wearing a distressed leather overcoat, a frayed scarf knitted in a zigzag pattern, and a waistcoat. (TV: The Name of the Doctor) He also wore also aged trousers, a box-frame belt with several fastener pins and studded pinholes, and combat boots adorned with weathered stirrups, which had a few buttons missing. (TV: The Day of the Doctor) His oldest article of dress was a bandolier across his left shoulder, taken off the body of Cass and equipped as an instrument for battle by him mere seconds after his regeneration was finished. (TV: The Night of the Doctor)

Behind the scenes

 * Hurt, aged 73 when he first appeared on screen, is the oldest actor to portray the Doctor upon their debut appearance. The second oldest would be William Hartnell, who was 55 years old when the show premiered in 1963.
 * Strax describes this incarnation of the Doctor as having "the look of a battle hardened warrior" in WC: Strax Field Report: The Doctor's Greatest Secret.
 * This incarnation of the Doctor is never named during The Night of the Doctor itself, but is described as the War Doctor in the end credits and on the official BBC website . John Hurt is listed as one of the actors playing the Doctor in the end credits of The Day of the Doctor.
 * Though John Hurt was 73 years old when he debuted as this incarnation of the Doctor, special effects were used to blend archive material of the actor from earlier in his life to depict the War Doctor as looking younger immediately after the Eighth Doctor's regeneration.
 * The War Doctor also shares certain characteristics with the Valeyard: he's a darker version of the Doctor who rejected the name of "the Doctor" and the expectations that go with it.