The Time War was a brilliant conceit that helped establish Doctor Who as a global hit, and Steven Moffat made it even better during his tenure as the series' showrunner. The Time War also served as a catch-all that could explain away any discrepancies in continuity between the original series and all the associated media, including tie-in novels, comic books and radio plays.
It would be fair to say that Doctor Who had an uphill battle finding an audience when it was first revived in 2005 by Queer As Folk creator Russell T. Davies. Many doubted that the BBC could revamp the classic science-fiction series after nearly a decade of inactivity as a regularly released television show. Thankfully, Davies proved the naysayers wrong, and was able to reintroduce the character of the Doctor and his police-box time machine, the TARDIS, to a new generation of Whovians.
The new adventures of The Doctor and his companions went on to become popular on a global scale. A good portion of the series' success can be attributed to the concept of the Time War, which ensured that those viewers who had never seen Doctor Who before could get into the series without any prior experience. Indeed, the Time War arranged it so that fans of the original series would approach the new episodes on equal footing with newbies, though with a greater appreciation of the show's legacy as the universe was reintroduced and expanded.
The Time War Explained
The first hint of the Time War's existence came in "Rose," the first episode of the revived Doctor Who, which centered upon a 19-year-old London shop-girl named Rose Tyler (Billie Piper). The episode introduced viewers to The Doctor (Christopher Eccleston) through Rose's eyes, as she was drawn into his efforts to thwart an alien invader. It was while confronting the aliens' leader that The Doctor made mention of having fought in a war and apologized for being unable to save the aliens' world, insisting "I couldn't save your world! I couldn't save any of them!"
More details came out as the series progressed, with The Doctor revealing to Rose that his planet had been destroyed in a war and that he was the last of a group called the Time Lords. The Doctor and Rose also encountered the Gelth; an alien race of gaseous beings whose physical bodies were destroyed during an event they called The Time War. This was later confirmed to be the same war that had destroyed The Doctor's homeworld, when he and Rose encountered a Dalek - one of the alien species of genocidal conquerors who were The Doctor's greatest enemies and the instigators of The Time War.
The season finale, "The Parting of Ways," revealed that much of the universe had been destroyed during The Time War, as the Time Lords and the Daleks battled across the whole of space and time, with entire species being retconned out of existence as both sides attempted to erase one another's potential allies and future battlegrounds from reality. In the end, The Doctor turned against his own people, undertaking some action that was meant to remove both the Time Lords and the Daleks from the universe while there was still a universe left to save. Though he had meant to die with his people, somehow The Doctor survived, remaining in the reborn universe as the last of the Time Lords.
How The Time War Shaped Rebooted Doctor Who
The idea of the Time War helped to develop the revamped Doctor Who by achieving three seemingly impossible goals. First, it helped to reestablish The Doctor as a figure of mystery after far too many stories had attempted to pigeon-hole his background and define his history. Second, the Time War helped to level the playing field between fans of the original series and new viewers, creating a new story that paid tribute to the legacy of Doctor Who while still being accessible to those who couldn't spot the subtle shout-outs to Genesis of the Daleks. Finally, the Time War created a handy excuse for explaining away any stories that seemed to contradict the greater continuity of the series as a side-effect of the Time War and an ever-shifting universe.
These ideas helped to develop the series throughout Russell T. Davies' time as Doctor Who's showrunner, all the way through the end of the era of the 10th Doctor (David Tennant). By making the series more accessible to new viewers, Davies helped to expand the audience, allowing Doctor Who to grow into an international sensation rather than a niche program that appealed to only a few viewers outside of the United Kingdom. Restoring the sense of mystery that had been an integral part of the series since the beginning and the idea of The Doctor being a semi-sinister being who couldn't always be trusted to do what seemed to be the right thing by human standards also endeared the revamped series to fans of the classic Doctor Who episodes.
How Steven Moffat Changed The Time War
While Davies concept for the Time War was ingenious, his successor, Steven Moffat, was able to build upon it brilliantly. One of the unfortunate side-effects of Davies' run was that he was forced to undo certain aspects of The Time War and his idea of The Doctor being the last of the Time Lords with every passing season. By the time Davies ended his run, both the Dalek Emperor and Davros were revealed to have survived the Time War, along with The Master. Realizing that the Time War had served its purpose, but that removing the Daleks and the Time Lords eliminated too many possibilities for future stories, Moffat began laying the groundwork to undo the effects of the Time War while still allowing its legacy to go on.
Moffat's grand plan began with the season 7 finale, "The Name of The Doctor," and the revelation that The Doctor had an unknown incarnation who had existed during the Time War. Played by John Hurt, this regeneration came to be known as The War Doctor, but he denied himself the name of The Doctor due to his abandoning his pacifist ways to fight alongside the rest of the Time Lords. This was further explored in "The Night of The Doctor;" a mini-episode starring Paul McGann's 8th Doctor. In addition to setting the stage for how The War Doctor was born, the special also gave McGann, who had only played The Doctor on film once in the failed 1996 pilot movie for a new Doctor Who series, a chance to film his Doctor's regeneration scene and officially bring his tenure as The Doctor to an definitive close.
"The Day of The Doctor" went on to establish that it was the War Doctor, rather than McGann's 8th Doctor or Christopher Eccleston's 9th Doctor, who was responsible for ending the Time War. As the Time Lord's homeworld fell under siege and the Time Lord's leadership began to consider drastic measures that would save them at the cost of the rest of the universe, The War Doctor stole an ancient Time Lord weapon known as the Moment, which could give its wielder the power to destroy whole galaxies and eliminate entire timelines. What truly made the Moment fearsome, however, was that it had developed sentience as well as a conscience, and it would punish anyone bold enough to use it. In the case of The Doctor, the Moment decreed that he would live on to bear the guilt of bringing about the genocide of two races, rather than dying with the rest of the Time Lords as he had planned.
However, before allowing itself to be activated, the Moment offered to show the War Doctor the men he would become in the future. This led to the War Doctor teaming up with the 10th Doctor and 11th Doctor (Matt Smith) after the three Doctors were brought together by a confluence of events. This was ultimately revealed to be the work of the Moment, who intended to give The War Doctor a chance to find another way to bring about the same ends without resorting to murder on an intergalactic scale. The final result was a cosmic shell game, which ended with The Time Lords safely contained in a pocket dimension, the Daleks largely destroyed and the War Doctor regenerating into the 9th Doctor, convinced he had used the Moment to end the Time War when he truly hadn't.
"The Day Of The Doctor" helped open the door to a new host of story possibilities making use of the Time Lords, the Daleks and other elements of the show's past. What is more, it also helped to restore something of the sense of mystery that many felt Doctor Who had lost. Nothing quite symbolized this so much as the episode's ending, in which the 11th Doctor was confronted by an old man who introduced himself as the Curator. Appearing to be an older version of The Doctor's fourth regeneration, the Curator hinted that The Doctor still had a great many adventures ahead of him, including finding the missing Time Lords and discovering a way to regenerate into forms he had held before. While it seems unlikely we may see this come to pass in the television series, Moffat's grand scheme for ending the Time War still resulted in an infinite horizon for future writers to explore.