Gears of Fallout
The current planet is Earth, and the year is 2010. Half of humanity is underground. The problem is, humans aren't the only thing underground. Below the surface is a network of denizens and locust caverns. Almost every reachable cave has an even deeper underground. The central area of the Locust threat is actually under Vault 18, where Vault-Tec attempted to create killing machines via F.E.V. Unfortunately, the experiments went incredibly wrong, and from the Vault, the mutants only went deeper. Originally they were greenish and quite large, but as evolution took its place, they began to change into http://www.wired.com/images_blogs/photos/uncategorized/2007/09/12/locust.jpg
Now, the year is 2277, and the Locust aren't happy.The war with China has ended in peace treaty, and all nuclear bombs have been stored for a later date, but not destroyed. You see America are sneaky bastards, they weren't willing to turn their back on any country, no matter how must trust was feigned on paper. But then again, thats human nature. Meanwhile, underground, the remnants of the F.E.V. has now formed its own civilization, and is ready to attack. The first sightings were in D.C., close to where it all started. In retaliation, the Brotherhood of Gears, or BOG, were formed. A war broke out between all of humanity and all of the mutants, who called themselves the Crogan. Eventually President of America, Matthew Eden sat down with John Fenix (Vice President), Adam Lyons (BOG Founder and leader/Secretary of Defense), and all other representatives of the world, and declared nuclear fallout, in which they would pull out all of their dusty warheads, and dropped them all over the world.
From then, war and chaos ensued. From the ashen tattered remains of the world, humanity tried to fight the rest of the Crogan off. [This is where it could break off into an RP or a fan-fic]