A war between the Daleks and a race of humanoid robots, the Movellans, has reached a stalemate. The Daleks, seeking a way to defeat their foes, returned to Skaro in an attempt to find their creator Davros to gain from him the knowledge needed to tip the balance of the war. The Movellans, meanwhile, capture the Doctor and attempt to gain the same information from him. The Doctor ends up escaping and capturing Davros without either side gaining the information they needed.
Although they do not appear in the Fifth Doctor story "Resurrection of the Daleks" (Doctor Who (1963) Season 21), it is revealed in it that the Movellans eventually defeated the Daleks by developing a biological weapon that targets the Kaled mutant inside the Daleks.
The Time Crash blog was created to help New Who fans understand Classic Who references - and to know if something isn't a reference but a new idea. If there's a reference I missed or a subject that you feel needs more explaining, please comment.