The Call of Duty World at war campaign features multiple combatants to play as.
Each campaign has it's own unique characters. Apart from the characters you play as, the main two characters are Sergeant Roebuck (played by Kiefer Sutherland) in the American campign, and Sergeant Reznov (played by commissioner Gordon from The Dark Knight, needs edit with actual name) in the Russian campaign.
Roebuck is a battle-heardened soldier who just wants an end to the war. He has dealt with loss, death, destruction, and pain. In the last mission, you must choose whether to save him by acting quick or letting him die.
Reznov is a die-hard Russian. He is loyal to the Motherland. Reznov despises Nazis with a passion. He is a cold-blooded, take charge guy. He doesn't care what the task will take; as long as it gets done. Reznov saves you from being murdered in the last moments of the game.