Pendulum Wars were fought for 85 years. During this time, what became the COG government decided to try and tip the scales by using a new biological weapon. They'd found tribal sub-humans underground, and started splicing their genes with humans to create bioweapons. Most of the experiments failed, and left the subject as a flailing psychopathic killer (Sires). Some experiments, however, were more successful, creating the Theron Guards/Sentinels as we know them today.
One experiment, a subject named Ruth, succeeded far beyond every other subject; she was the perfect match and ended up with the durability of the sub-humans with the intellect of a human. Adam Fenix was working as a researcher here, and when he saw what happened to Ruth (a companionship had come between them), he quit the COG as soon as possible. Ruth, now the locust queen, broke out of the research facility with her new Guard of intelligent Locust, and went back down underground.
As the years pass, the newer, smarter locusts start to subjugate the tribal locusts of before (the ones responsible for the majority of the Hollow). These Locust become drones, wretches, Boomers, and so on. Ruth learns through the culture of the Locust just how evil humans really are, and, partly because of her new standing, vows to wage war on humanity.
These events lead up to Marcus' dereliction of duty (to save his now suicidal Father from dying on the battlefield), and later E-Day, and so on.
I don't have anything written down, for obvious reasons, but as your usual intern I was forced to get coffee for the guys, run errands, and take notes during story meetings. That's where most of this came up.
It's a pretty bad story I think, but the target audience is a little low-brow in that department.
Really? GoW decided to go with the, "Experiment gone wrong" genre?
Well, it's more of an experiment gone right, along with a theme of global karma.
Personally, I always preferred another story option that, in summation, had Locusts and Humans swapping places several hundred times through history as one was driven below ground and the other claimed the surface.
That got scrapped pretty quick though, it was kind of hard to follow.
and its not hard to figure out if you play story mode
Well, to be fair to Epic, that was never the intention. That's why the earlier story got scrapped almost as quickly as it was articulated: Gears is a game that's meant to be a lot like a Summer action flick.
Easy to digest story, simple characters, lots of special effects.