MovieBuff09

Chosen answer: The Eighth Doctor regenerated because he died in a crash on Karn, where the Sisterhood revived him to offer him the choice to either die, or regenerate to fight in the war. He choose to become the War Doctor, who regenerated after the events of "The Day of the Doctor" due to the stress of the Time War, or maybe because the war was over, and there was no need to be a warrior anymore.

Chosen answer: Few details have been revealed within the show itself, although Russell T Davies has given a few pointers in an article that he wrote for a Doctor Who annual. He suggests that the Daleks consider the War to have begun with the Time Lords sending the Fourth Doctor back to interfere with their creation, as seen in Genesis of the Daleks. The Daleks took this personally and first tried to replace prominent Time Lords with duplicates, in a similar fashion to their attempt to infiltrate Earth as seen in Resurrection of the Daleks. A peace treaty was attempted, with both sides offering compromise (the Time Lords, for example, handed over the Master for execution, as seen in the 1996 TV movie), but ultimately failed, leading to escalation and eventually the declaration of full-scale war between the races. The war apparently lasted for several years, if a war that takes place on a temporal level can really be said to have a set duration, before the Doctor brought it to its apocalyptic conclusion of destroying all Time Lords and Daleks, as seen in "Day of the Doctor."

Tailkinker ★