- We just heard a declaration of war... and maybe some of us here also believe we heard a sentence of death for the human race.
The roots of the Earth/Mars War go back to the extinction of the Martian culture in 1969. An ambitious Martian military leader named Commander Blanx destroyed all life on the planet Mars by way of something called the "Blue Inferno". However, not all Martians died during the event. The Manhunter, J'onn J'onzz had already escaped to the planet Earth many years earlier, but there was also an entire colony of Martians that were forced to abandon their home world just to survive.
These Martians later reunited with J'onn J'onzz during a time when he was serving as a member of the Justice League of America. J'onn left the team in order to help the Martian refugees establish a new home for themselves in the Cygnus system dubbed Mars II. During this time, J'onn fell in love with a young Martian woman named J'en. He was elected a leading member of the new Martian council and remained with them for many years.
A Martian military officer known only as the Marshal proved to be an ambitious and charismatic leader. A product of genetic perfection, the Marshal managed to rally all of his "red brothers" together and staged a coup against the reigning Martian government. The Marshal had learned about the Viking I space module that Earth had sent to the surface of Mars, and believed that the Earthlings were using "robot slaves" to rape the surface of the planet. In his perception, such an act was to be considered an open act of war. It was his directive to return to the Sol system and conquer Earth. Faced with overwhelming odds, J'onn J'onzz had little choice but to flee Mars II. The Marshal and his followers discovered J'onn's alleged treachery, and followed him to Earth.
J'onn's ship barely survived the journey, and he crash-landed in New York's East River. He reunited with his old colleagues in the Justice League and warned them of the pending Martian invasion. The Marshal sent a robotic valet known as the Challenger to Earth to deliver the Marshal's ultimatum. In exchange for an unconditional surrender, the Challenger decreed that Earth's population would be allowed to live, albeit in controlled concentration camps. Refusal to submit to Martian control would mean their lives. The governments of Earth refused to yield to Martian persecution and thus the war for Earth began.
The Marshal sent a fleet of ships to surround the planet. One by one, they began destroying Earth's satellite network. Hawkman and Hawkwoman attempted to stave off the Martian onslaught in their small Thanagarian vessel, but even their valiant efforts were not enough to save the Satellite from destruction.
Earth's governments responded as well, as American and Soviet forces worked together to repel the invaders. For all their bravery, however, their arsenal was simply not enough to cause any significant damage.
Aquaman gathered together his fellow Justice League members in an effort to reclaim the ruins of the JL Satellite. The Marshal sent the Challenger to intercept them and the robot warrior easily dispatched Aquaman and the Red Tornado. Green Arrow managed to stop the Challenger with a wall-smasher arrow, but Aquaman was furious over how unprepared the League was in dealing with this crisis.
The Martian Manhunter took one of the surviving League shuttles and directly engaged the Martian fleet. In a video-feed battle broadcast across the entire fleet, J'onn faced the Marshal in mortal combat. The Marshal employed powers of invisibility against the Martian Manhunter – practice considered dishonorable in trials of combat. Despite such a disadvantage, the Manhunter succeeded in defeating him, and the Marshal lost face before the entire Martian fleet. J'onn addressed the fleet and convinced them that following the Marshal was wrong, and that Earth is not their enemy. Ashamed, the Martians agreed to a cease-fire and retreated from Earth.
Knowing that there was no longer a place for him among his own people, the Martian Manhunter elected to stay behind on Earth. However, the Justice League that he had been a part of for so long was destined for a different fate. Aquaman, the only original team member present during the Martian invasion, realized that Earth's chances would have been stronger, with a fully committed JLA roster leading the charge. Feeling as if the group no longer functioned effectively in its present state, he disbanded the Justice League of America.
- Due to numerous alterations in the history of the Martian Manhunter, the Earth/Mars War is no longer considered part of current continuity. In order to re-establish J'onn J'onzz as the "Last Son of Mars", writer John Ostrander, re-imagined the details behind the war, replacing the Martian Warriors with a fleet of inter-planetary exiles known as the Debris. 
- No trivia.