It looks like Guerilla Games is finally exploring the hazy morality that they put into the original backstory but ignored in the good guys vs bad guys plot of the games.
If the backstory of Killzone was compared to Earth history, then the Helghans are basically colonial America and the UCA/ISA (side you fight for) is the British Empire. The colonizers turn America into a booming economic hub. Britain decides to increase taxes and regulations to keep America under control. America revolts, except in this story, Britain wins, takes over the original colonies, and forces all the colonists to migrate to the least hospital parts of the continent where all who can't adapt die of starvation and exposure. Over 100 years later, the rugged surviving colonists have gotten back onto their economic feet, but the British Empire uses its power to enforce unfair trading arrangements, which plummets them into a depression and causes widespread famine and poverty. This allows a charismatic leader to execute a popular coup and establishes a military state which can fight back against the British Empire. After biding their time and building up forces, the colonists launch an assault to take back the lands they were expelled from. Now you, Captain Jan Templar, are tasked with defending our peaceful empire from these evil Nazi weirdos who have attacked us for no reason.
Um... ok. God save the King and fuck those Nazis!