It is the fourth installment of the Call of Duty video game series, excluding expansions. It is also the first one to break away from the World War II setting and to be set in modern times, and the first game in the series to be rated Mature in North America. The title and game details were announced on April 25, 2007, while it was released worldwide between November 6, 2007 and November 9, 2007, and became available on Steam on November 6, 2007 for pre-purchase, becoming available to play on November 12, 2007. A Mac OS X version of the game is scheduled to be released in May 2008.
The story is set in a fictional near-future war between the United States, Europe, and Russian Loyalists against Russian Ultranationalists and Middle Eastern rebels, and features real-world weapons and vehicles. It is told from the perspective of both a United States Marine and an operative of the British SAS, and is set in multiple locations, including the Middle East, Azerbaijan, Russia, and Pripyat. Its multiplayer features different game modes and contains a leveling system, which allows the player to unlock additional weapons, weapon attachments, and camouflage schemes as they advance.