An alternate timeline was created when the Seventh Doctor's TARDIS was trapped in the Temporal Plexus. When the TARDIS from the future entered the Plexus, due to the Doctor creating a supernova to leave, the timelines of the TARDISes became tangled, the energy release creating an alternate timeline.
In this timeline the neutron war on Skaro was apparently accidental. Though the Daleks still developed, in this timeline they became peace-loving academics. Skaro was the universal centre of civilisation, philosophy, democracy and art, visited from all over the universe. In the normal timeline the Daleks wiped out the natives of the planet Markhan. However, here, 200 years after the Markhan Genocide happened, the Markhan inhabitants still existed, some even living on Skaro. The Time Lords were on good terms with the Daleks, their President having been cured by Dalek surgeons. The Cybermen and Sontarans were still a dangerous force in this universe, meaning the Daleks had armed space stations.
There were other differences. The planet Sussashia Four was destroyed, meaning the reticulated sheep of Chonev were extinct. The Sontarans won the battle of Kharax Rift, and the Suxora Empire never fell, but the Kligoric Imperium did.
However, this timeline was unstable. The Daleks detected star systems were being erased from existence, and solar activity from their star began to increase. The Doctor travelled back to the Temporal Plexus and prevented the timeline being formed. (PROSE: The Ripple Effect)