White haired dude got caught screwing the kings daughter. His troops were led to ambush and mostly killed. White haired dude then got sent to prison for a year or two to be starved, tortured and mutilated.
When the other guy caught up with the remnants of their army, they went and busted him out. Then the white haired guy accepted the offer to ascend to a demon-god, sacrificed his remaining troops to demons as an offering, raped the other guy's girlfriend (who was also white haired dude's most loyal ally) in front of the other guy's eyes (well a single eye since one was being gouged out by a demon at the time).
And that's when the story REALLY starts.