It was widely assumed prior to 2013 that either the Eighth or Ninth Doctors - or both - were the ones that directly fought in the Time War. With the revelation that there was a secret incarnation between them, it suddenly became much more interesting. The Moment was a weapon of mass destruction that grew a conscience which dictated to the Doctor that he would live with regret if he eliminated not only the Daleks, but his whole entire race as well. Thankfully, the history that the Ninth and Tenth Doctors remember did not actually come to pass, and Gallifrey is safe once more, albeit lost in a pocket universe.