Time war

 ''This article is about the concept of a time war in general. For the Time War involving the Daleks that resulted in the near-extinction of the Time Lords, see Last Great Time War.'' 

A time war could be one of at least two types of time-spanning conflicts. The first type of time war was where sides fought each other across different points in history. The second type of time war was one in which time itself was used as a weapon by two or more time-active factions, employing preemptive strikes, time loops, temporal paradoxes and the reversal of historical events. It is difficult to study these wars, since they tended to erase the damage before it was made.

The first time war fought by Gallifrey was the Black Sun War, starting when the Order of the Black Sun sent a time-travelling assassin to prevent Gallifrey from gaining time travel. (COMIC: Star Death) The Order itself existed 30,000 years in the future, and launched a second attack twenty years later. (4-D War) The Time Lords had been viewed by the Order as striking first in the present, thanks to a Sontaran scheme. (COMIC: Black Sun Rising)

A second war, lasting thirty thousand years, took place a generation after the time of Rassilon. It was fought between the Time Lords and other races that were developing time travel. The Time Lords destroyed one such race, the Charon, before they even existed. (PROSE: Sky Pirates!)

At one point in the Doctor's future, a war was fought between the Time Lords and the Enemy (who had no other known name). Although Gallifrey was also destroyed as a result of the Eighth Doctor attempting to prevent the war from beginning, (PROSE: The Ancestor Cell) this was a different event from the Last Great Time War with the Daleks, which also destroyed Gallifrey. (TV: The End of the World onwards)
 * At some point, Gallifrey was possibly restored, only to be destroyed again in the Last Great Time War.

Behind the scenes

 * A fan-turned-pro, Russell T Davies has considerable knowledge of the mythology of the Doctor Who universe and knew about Gallifrey's previous destruction in The Ancestor Cell. In one of his regular Doctor Who Magazine columns, he compared Gallifrey being destroyed twice with Earth's two World Wars. He also said that he was "usually happy for old and new fans to invent the Complete History of the Doctor in their heads, completely free of the production team's hot and heavy hands." Despite Davies' unequivocal statement that the two wars are not the same, Lance Parkin, in his DWU timeline AHistory, suggests in a speculative essay that the "two" destructions of Gallifrey could be the same event seen from two different perspectives, with the Eighth Doctor present twice (and both times responsible for the planet's destruction).
 * The Doctor Who Annual 2006 describes two other time wars - one between the Halldons and the Eternals and the "brutal slaughter" of the Omnicraven Uprising; on both occasions, the Time Lords eventually stepped in to settle matters.