"Killzone 2 is a first-person shooter for the PlayStation 3, developed by Guerrilla Games and published by Sony Computer Entertainment. It is the third installment in the Killzone series that began on the PlayStation 2 with Killzone and continued on the PlayStation Portable with Killzone: Liberation. The game was first announced at E3 2005, with a tech demo on display, while the first gameplay footage was shown two years later at E3 2007. Killzone 2 was released worldwide late February 2009.
Killzone 2 follows the events of Killzone and Killzone: Liberation, and is set entirely on the planet Helghan, the home-world of the Helghast who invaded an Interplanetary Strategic Alliance (ISA) colony. Two years after the Helghast assault on Vekta, the ISA had launched an assault on the enemy's homeworld of Helghan. The ISA goal is to capture the Helghast leader, Emperor Scolar Visari, and bring the Helghast war machine to a halt. Players assume the role of Sergeant Tomas "Sev" Sevchenko, a battle-hardened veteran of the special forces unit the "Legion" assigned to Alpha team, who goes on a mission to take out the Helghast threat.
During the invasion of Helghan, Sev's unit is deployed behind enemy lines to assist the main invasion force. Tasked with securing the enemy capital of Pyrhus, Helghan's first true city, the team quickly discovers that the Helghast are a more formidable enemy on their home planet. Not only are they well-adapted to Helghan's hostile conditions, they have also harnessed the power of the freakish lightning storms that always occur on Helghan which they can now use against the ISA. A cold, barren, unforgiving world, Helghan provides a ready defense with thick, acidic air, dust clouds, and violent surgical lightning storms. Sev discovers his squad is not just fighting enemy forces—their fiercest opponent may be the planet itself.
There is both a lengthy campaign mode and 32 player multiplayer. Warzone, the title of the online multiplayer component of Killzone 2 has been developed by Guerrilla Games in conjunction with the game's single-player campaign. The online multiplayer gameplay is class-based, meaning the player can choose a class of character which is specialized for a specific role to better suit the player's needs in battle. There are 7 classes in total, in which the player can mix and match two according to their playing style, and can switch abilities upon death.
Warzone plays out through dynamic matches where multiple game types are played in a single round. The game ships with five different game types including Assassination, Search & Retrieve, Search & Destroy, Bodycount and Capture & Hold. Online matches can connect 2 to 32 players, and they can group into six squads of up to four players. If an online match does not have a full 32 players, computer-generated "bots" can be added in to create bigger teams (but only in an unranked match). Killzone 2 also offers a clan system, which allows clans of up to 64 players to compete for "Valor Points", an in-game currency that clans can use to bet on tournaments. When playing online a player can search for a specific game type if they want, for example, if a player only wanted to play bodycount they could search for that and the available games would appear."
Source: Wikipedia, "Killzone_2," available under the CC-BY-SA License.