The Magic Wars refers to two events: one specific and one broader:

The first event referred to by historians as the Magic Wars was that belonging to the first part of the Magic Inquisition, which ended with the Grand Inquisitor's occupation of Port Foozle on 34 Frobuary 1067 GUE. (see 'Second Inquisition' for more information).

Most commonly when historians refer to the Magic Wars, they refer to the period of the Magic Inquisition (which includes the above Magic Wars), and the acts of the Fourth Dungeon Master (closing the Age of Science, protecting the Underground from greedy trespassers, quelling a Granola Rebellion), which concluded with an epic confrontation between the Eastlands (the good guys) and the Westlands (the bad guys). Most details of these acts outside the closing of the Age of Science are non-extant, save for a single fragmentary mention of the conflict.

SOURCE(S): Zork:Grand Inquisitor, Magic Wars Trilogy (short press release)