The Last Great Time War pitted the Time Lords of Gallifrey against the Daleks of Skaro. The specific incident that sparked the conflict remains unclear, but according to executive producer Russell T Davies, the origins dated back to conflicts between the Doctor and the Daleks. In "Genesis of the Daleks" (1975), the Time Lords—having foreseen the possibility of the Daleks conquering the universe—send the Fourth Doctor into the past in an attempt to avert the Daleks' creation, affect their development to make them less aggressive, or discover an inherent weakness they could exploit.