Call of Duty: Modern Warfare takes place in a realistic and modern setting. The campaign follows American CIA officers and British SAS forces as they team up with rebels from the fictional country of Urzikstan, combating together against Russian forces who have invaded the country. The game's Special Ops mode features cooperative play missions that follow up the campaign's story. The multiplayer mode supports cross-platform multiplayer for the first time in the series. It has been reworked for gameplay to be more tactical and introduces new features, such as a Realism mode that removes the HUD as well as a form of the Ground War mode that now supports 64 players.