Turn A Gundam I: Earth Light.

Loran Cehack is a spy sent from the moon to scout out Earth, whom they plan to invade. He grows to love Earth as his true home and, after discovering a giant mech from the dark ages, he begins to defend Earth in the war. The year is C.C. 2345. Growing tensions between the Earthrace and Moonrace have spiraled into an all out war. Mankind's only hope for peace lies with a young Moonrace boy named Loran Cehack, and his mysterious Turn-A Gundam, a relic of a dark history which nearly destroyed the Earth centuries ago. As a citizen of the moon, Loran is loyal to the beautiful Queen Dianna Soreil, all the while fighting to keep the technologically superior Moonrace at bay as the pre-industrial Earthrace tries desperately to catch up.