Call of Duty: World at War is a first-person shooter set during World War II and based on several historical battles. The action switches between three playable characters and covers the Pacific Theater and Eastern Front. The story begins with U.S. Marine Private C. Miller who is captured by the Japanese and waits for execution. Later it jumps over war theaters and the timeline, skipping entire months.
The battles in World at War are quite realistic, with the maximum of two weapons you can carry plus hand grenades. AI allies fight alongside to you, and there's also a cover system that helps to restore health and complete stealthy missions. The variety of levels includes PBY missions, sniper tasks, and sea battles. 
World at War is the first game of the franchise to introduce Nazi Zombies mode - a cooperative mini-game where 2 to 4 players fight endless hordes of zombies. While the area cover in this mode is quite small, it was expanded by the World at War map packs.