Dalek invasion of Earth (Mission to the Unknown)

As both Gordon Lowery and Marc Cory understood in the year 4000, the Daleks had invaded Earth a thousand years prior before they disappeared from human space. (TV: Mission to the Unknown) By another account, Lowery stated that every schoolkid knew that the Daleks invaded Earth "a couple of times, and were beaten back", with not much having been heard about them since the Movellan Wars a thousand years prior. (PROSE: Mission to the Unknown)

Although they stayed clear of the galaxy of Mutter's Spiral in the years that followed, the Dalek Empire expanded throughout the Outer Galaxies; in half a millennium leading up to 4000, they gained control of over 70 planets in the Ninth Galactic System and 40 more in the Constellation of Miros. (TV: Mission to the Unknown)

Behind the scenes

 * The Dalek Handbook states that, long after the 26th century conflict and the Exxilon Gambit, the Dalek Wars ended with another short-lived invasion of Earth (following the 2150s Dalek invasion of Earth) around the year 3000, after which humanity saw little to no Dalek activity for 500 years.