War Doctor

The "War Doctor" was the incarnation of the Doctor that saw the most direct combat in the Last Great Time War. (TV: The Day of the Doctor) This incarnation, originally young and robust, disowned the name of the Doctor because he felt unworthy of it. He spent countless years waging war. After becoming old and tired of battle and faced with the end of reality, this Doctor activated the Moment, and thereby committed genocide against both the Daleks and his own people.

For hundreds of years, later incarnations of the Doctor disowned the War Doctor in a vain effort to drive the horrible acts from their memories. When, however, the Tenth and Eleventh Doctors met him, an opportunity presented itself in which they could jointly rewrite their own personal histories. They availed themselves of this slim hope, and found a way to store Gallifrey into a pocket universe. Thereafter, the War Doctor was remembered as a genuine incarnation of the Doctor, but only by the Eleventh — and presumably later — Doctors. Thus, the Ninth and Tenth Doctors still believed the War Doctor was responsible for Gallifrey's fall. (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. They offered to control his regeneration so that he could 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 a potion offered by the Sisterhood, 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 Sontarans told legends of the Doctor leading Time Lords into battle. (TV: The Sontaran Stratagem) 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)

This Doctor became known to the Time Lords as "the Renegade", and destroyed Gallifrey and ended the Time War using the Moment. (COMIC: Sky Jacks)

Meeting with the Eleventh Doctor
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 unknown 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 unknown incarnation turned around and watched them with a sombre stare. (TV: The Name 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 tenth incarnation, but the ninth to call himself "the Doctor". Sadly, this new incarnation lost the crucial memories of how the Time War truly ended, believing he had killed his people, which left his spirit terribly wounded. (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
His actions tormented many future lives of the Doctor, who were haunted for centuries on end by the dual genocide he orchestrated. 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)

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)

Appearance
The War Doctor appeared old and bedraggled, wearing a distressed leather overcoat and a waistcoat. (TV: The Name 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.

As shown immediately after his regeneration, this Doctor actually regenerated to a very young age, and seemed to have aged far more than any previous incarnation (other than the first) during his life. (TV: The Night of the Doctor)

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)

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. 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 with a younger appearance at birth.
 * 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.

El Doctor (The Name of the Doctor) Доктор (Имя Доктора) הדוקטור (השם של הדוקטור)