Yeah I remember reading all of the story pieces on the official site awhile ago. When Earth started expanding to out space the main goverment ran out of funds or something and the Helghast company (started out as a simple company) had tons of funds so I can't quite remember how but basically the government screwed the Helghast company over, kicked them off of Vetka (the good planet) and forced them to live on a planet that had very poor living conditions. It burned their longs and a lot of them died on the barren planet.
I believe the invasion during Killzone 1 is the Helghast trying to take back the planet they rightfully founded.
Pretty sure that's how it goes but it has been years since I read the lore so i'm probably a little mistaken with some parts. I would totally love to play as the Helghast though, and see their side of the struggle. Also, Rico is a gigantic bag of douche!
