The Galactic Wars were a series of galactic-level conflicts. Because of the number of deaths during the wars, graveworlds were set up to honour the fallen. Graveworld 909 was established during the Seventh Galactic War. (COMIC: Onomatopoeia)
Beginning in 2540, the intermittent "Galactic Wars" were fought as the Daleks fought Earth and its allies for dominion of the galaxy of Mutter's Spiral. (PROSE: Beige Planet Mars, TV: Frontier in Space)
Behind the scenes[]
In a 1966 production note, a "galactic war" is said to be the cause of the First Doctor and Susan Foreman's departure from their then unnamed home planet, and one of the "unendurable" events of the Doctor's life which are re-lived during the "metaphysical change". (REF: The Second Doctor Handbook)