Call of Duty military advisor Hank Keirsey has defended the series' return to its World War II roots, claiming: "we're not going back; we didn't finish telling the story".
The retired lieutenant colonel told Eurogamer TV that he and developer Treyarch had been inspired to focus on the Pacific theatre by interviews with 15 marine veterans of the conflict, which "convinced me that we need to tell the story in a game."
The bulk of the game's campaign mode focuses on the battle between the US marine corps and Japanese forces, which Keirsey described as a "different enemy: relentless, tenacious," that, as a result, changes the game experience.
"[It was a] very difficult fight, a very close fight, and a very gritty fight - Treyarch did a good job of bringing that fight out and telling the story."
With Call of Duty series creator Infinity Ward busy working on a follow up to last year's acclaimed Call of Duty 4: Modern Warfare, development duties for World At War were passed on to Treyarch, developer of Call of Duty 3.
"Treyarch put out [COD3] in eight months," said Keirsey. "And for an eight month product, they put out a hell of a game. But now they've been given a two-year development cycle, so the lads were actually able to put a lot of polish on this game.
World At War will carry an 'M' rating in the US, which has allowed Treyarch to "bring out the intensity that those marine veterans talked to us about," according to Keirsey.
"The only thing we're missing is the smell, the heat, the bodies being rotted with maggots crawling over them, and we're putting that together in an expansion pack," he quipped.
Call of Duty: World At War is out on PS3, 360, PC and Wii later this year. You can see more from our exclusive interview with Hank Keirsey over on Eurogamer TV.