The Story: "...And So My World Ends!" by Denny O'Neil, Dick Dillin, and Sid Greene. Guest-star Diana Prince runs afoul of a mysterious cloaked man wrecking the fire-eating sideshow at the circus(!) Prince and her mentor I-Ching(!!) are attending. When Prince is easily knocked aside by the stranger, she calls in the JLA for help.
The JLA show up and they learn that this mysterious stranger is...the Martian Manhunter!!
They ask J'onn where he's been, since they haven't seen him for months(he last appeared in JLA #61), and he tells them he has been trying to prevent a murderous Martian named Blanx from taking over Mars by killing its citizens and destroying its resources. He asks the JLA for help!
They go to Mars and take on Blanx's army, but its up to Manhunter to take on Blanx personally. It's grim, hand-to-hand combat, but finally J'onn defeats Blanx. Unfortunately, Blanx has wreaked massive destruction on Mars, far beyond even what he had planned, leaving the entire planet dead. Superman informs J'onn that some of his people escaped via a spacecraft that J'onn had built for just such a purpose. He resolves to find those people and bring them back to Mars to rebuild, which means he has to leave his adopted planet Earth and his friends in the Justice League:
Roll Call: Superman, Batman, Flash, Green Lantern, Martian Manhunter, Green Arrow, Atom, Hawkman
Notable Moments: Aquaman is the only member of the team not participating in this story---rats!
Denny O'Neil was affecting all kinds of change, barely a year into his tenure as JLA writer. Two powerful, founding members gone, and of course even more change was in store...