Call of Duty 4 Modern Warfare

In Call of Duty 4, the player assumes the role of two characters in the fictional war that takes place in the game. Sgt. John "Soap" MacTavish, a member of the British S.A.S. and Sgt. Paul Jackson, a member of the United States Marine Corps. Though missions for both characters take place in different locations they are both fighting toward the same goal; to stop the terrorist forces of Khaled Al-Asad and Imran Zakhaev from using a nuclear weapon they have obtained.