Gameplay
Call of Duty: World at War will feature a more mature theme than previous installments in the series. Swimming elements will be introduced to the series for the first time in single player and multiplayer. While in water, the player cannot sprint and will only move at half speed.[8] Flamethrowers, first introduced in Call of Duty: United Offensive, will be reintroduced with new flammable environments. The game will be slightly more open-ended than previous games in the series, as there will be multiple ways to complete missions.
Multiplayer
World at War will feature cooperative gameplay (four players via split-screen (on consoles) or four players online) for the first time in the franchise. Cooperative multiplayer on the Wii will allow for multiple players to play on one screen, with gameplay sients within multiplayer. It will also use a perk system similar to Infinity Ward's Call of Duty 4.Activision has confirmed the presence of vehicles in multiplayer.[Multiplayer games will also have destructible environments that will break down when you shoot them or explode when you drop a grenade near them.
Plot
The story mode features two campaigns, the United States Marine Corps battling the Japanese Imperial Army in the Pacific, and the Soviet Red Army on the European Eastern Front towards the end of the war. One part of a level entitled Makin Raid shows an Allied prisoner of war being tortured by the Japanese before having his throat slit by a katana. The player's character witnesses this scene and is later rescued by U.S. Marines who liberate the camp.Two other levels were revealed by IGN: one involves the player using the machine guns on a PBY Catalina to attack a Japanese naval fleet, and the other shows the beginning of the Russian campaign. In that level, the player and a Russian sniper attack German troops under the cover of a bombing raid.
-wikipedia.com