Set in the near future, in a period of planetary colonisation, it revolves around a savage conflict between forces that are still loyal to Earth (the ISA) and a separatist, militaristic faction who call themselves the Helghast. The game follows your squad of four soldiers on a suicidal mission behind enemy lines, as they fight to undermine and defeat the Helghast forces following their devastating Blitzkrieg attack on the human colony.