Secret Origins #32

Synopsis

Contenders for the leadership of Appellax stage their combat on Earth through "battle form" surrogates, the Martian Manhunter, Aquaman, Black Canary, the Flash, and Green Lantern first encounter and defeat the first 5 individual battle forms separately, but have to work together to defeat the sixth one. As they are about to face the seventh one in Greenland, they arrive to see Superman finishing up defeating it and flying off. This experience gives them the idea to join together as the Justice League of America.