The escalating conflict between the ISA and the Helghast plays out on a much smaller scale in Killzone Universe, a live-action short that shows a friendship torn apart by impending war.
For those unfamiliar with the back story of the Killzone series, the Helghast were once part of the Helghan Corporation, a commercial outfit that purchased two planets in the Alpha Centuri system from Earth, after the planet's forces failed to reach the system due to a devastating solar storm.
The Helghan company took advantage of its position, controlling one planet - Vekta - with an iron fist, with establishing a tiny outpost on the unnamed second planet, a toxic wasteland.
Tax issues led to a conflict between the Helghan Corporation and the ISA military organisation, leading to the company being exiled to the second planet, now dubbed Helghan.
The Killzone games document the main conflict. This Killzone Universe short shows how the situation affected a pair of friends, one exiled to Helghan, the other safe and secure on Vekta. It's just a quick peek at these two lives, but it adds a great deal of humanity to the franchise in the process.
Killzone Universe Video Shows Life Before Killzone 3 [PlayStation Blog]