- You may be looking for the Millennium War.
Having temporary control of the Event Synthesizer and therefore over reality itself, the demon Melanicus instigated, for no other reason than to do it, the Millennium Wars, encompassing a thousand different worlds and a thousand different time periods. (COMIC: The Tides of Time)
The worlds ruined by the Wars included a future Earth. (COMIC: The Tides of Time)
The Fourth Doctor was briefly caught in one of these conflicts, not understanding its significance. (COMIC: The Deal)