In the history you know, on this day in 1938 Martians landed in Grover's Mill, New Jersey to begin an invasion of the Earth. Fortunately for humanity their conquest was thwarted when they proved susceptible to our planet's microorganisms and their entire invasion force died. But now, on the anniversary of their first invasion attempt, they have returned to try again. This time they have immunized themselves against our germs. What's worse, they haven't come alone. With them are forces from every version of Mars that has ever attacked our world or our people.

Fortunately for us, we too have new allies to defend us. Every military force, organization or hero group in the Omniverse that has defended an Earth against alien invaders has answered our call for help. Together they will do their best to protect humanity, defend our civilization and repel these invaders from the planet. The question is whether they will succeed and what condition will our world be in once the fighting is over.

Only Martians who have either invaded our world or exhibited hostility to humanity are part of the invasion force. Friendly Martians like J'onn Jonz are not participating.

Only heroes and organizations which have fought against an actual attempted invasion of Earth are defending the world. Those who just fought a handful of alien villains just visiting to cause trouble but not attempting planetary conquest are not included.

I, The Watcher, pose this question to you all,

What If Every Hostile Martian Ever Attacked Every Defender of Earth?