Killzone is a first-person shooter exclusive to the PlayStation 2 game console, developed by Netherlands-based Guerrilla Games and released on November 2, 2004 in North America. A sequel, Killzone: Liberation was released on the PlayStation Portable and another followup, Killzone 2 was released for the PlayStation 3 on February 27, 2009. Killzone 3, the fourth installment in the series, was released February 22, 2011. The games are First Person Shooters based (except Liberation) in a SC-FI setting and the series is currently exclusive to Playstation. The game is set in an era of space colonization where the Helghast Empire has recovered from its defeat in the First Extrasolar War and launched a blitzkrieg against the outer Interplanetary Strategic Alliance (I.S.A.) colony planet Vekta. Vekta's orbital Strategic Defense (S.D.) platforms failed during the initial assault, allowing the Helghast to land swarms of soldiers onto the surface and making it all the more difficult for the outnumbered I.S.A. forces. In the game, the Helghast are a faction of human descendants who colonized the planet Helghan many generations ago. The planet's harsh environment forced the Helghast to adapt and mutate so much that they can no longer be considered human. They are stronger, faster and more resilient than their human cousins, and possess a burning hatred for humanity. Except for a small number of half-breed Helghast and trained troopers, they require a gas mask and air processing tank that creates air similar to that found on the planet Helghan. Earth, after a serious nuclear war between its nations, formed a major government of the richest surviving governments and industries to explore space colonization, eventually settling a solar system outside of Sol. Alpha Centauri is a system with two planets, the lush and blossoming Vekta, the other rich in energy supply but inhospitable; Helghan. These two planets were purchased by the Helghan Corporation after the UCN (United Colonial Nations) decided to auction them. However, after Helghast's economic policies threatened to undermine the UCN's financial system the UCN invaded Vekta and removed the Helghast after failing to impose financial sanctions. This forced the Helghast to colonize Helghan, a harsh and brutal planet, and deeply resenting the loss of Vekta.The player takes control of I.S.A. Captain Jan Templar, who is desperately repelling the invasion. Despite the I.S.A's efforts, they continue to suffer losses and the Helghast slowly prevail. Templar and his squad are called back to the base for reassignment. However, the I.S.A headquarters is overrun by the overwhelming assault force of the swarming Helghast and a forced evacuation was conducted. Templar managed to hold off the invasion with the help of Marshal Lugar. Templar and Lugar are then sent to find the I.S.A. operative Gregor Hakha, a half-Helghast spy who had acquired data on future Helghast movements. On their way they meet Ricardo Velasquez; another I.S.A soldier who had just lost his platoon to Helghast forces.As they meet up with Hakha, the unit discovered that General Stuart Adams, a high ranking ISA officer, was a traitor. When the Earth Defense Fleet (EDF) arrived to assist the Vektan Army, Adams murdered General Vaughan and prepared an ambush for the EDF relief force. A series of climactic and epic blockbuster conflicts unfold across the docks and other parts of Vekta as the small but specialised unit help regroup ISA with strategic strikes. During the invasion, Hakha confronted and killed Lente while the I.S.A unit was able to call off ECA attacks on the station. Templar and his unit managed to breach and destroy the station and Adams after a fanatical resistance. The battle weakened the Helghan, but their grip on the southern parts of Vekta remained unwaveringly strong and resilient as I.S.A forces regrouped and prepared to finally reclaim their planet.