Millions of years ago both white and green martians were exploring other worlds including Earth and Saturn. Both races started using cloning to make a work force. While the green martians treated the clones as equals, the white martians treated them as slaves. This lead to a civil war. When the war was over, the victorious green martians banished the remaining 70 white martians to the still zone (their name for the Phantom Zone).
Extricating themselves from the Still Zone aka Ghost Zone or Phantom Zone, the White Martians returned to Earth in the guise of gods calling themselves the Hyperclan, basing themselves in the 5000 year old martian city called Z'onn Z'orr in Antarctica. The Martians claimed their homeworld had been destroyed by negligence and greed and they offered to save Earth from a similar fate. The Hyperclan turned deserts into verdant paradises and ended crime by executing meta-criminals. This was all part of their insidious plan to discredit and destroy the Justice League. Earth's real heroes, with Batman as a spearhead, saw through this ruse and put a stop to it right away. All hope seemed lost after the White Martians took away the only means of defeating them, by burning them with fire. The Martians took this away from Earth by inhibiting the Earth's atmosphere with subatomic particles that inhibited any combustible reaction. To find a way around this, the Justice League lured the Martians to the Justice League Watchtower and defeated them there. Instead of sending them back to the Phantom Zone, J'onn brainwashed them into thinking they where humans and released them to live among humans.