Before Sledgehammer got the chance to work on Modern Warfare 3, they were hard at wok on their own action adventure Call of Duty title which was going to take place in Vietnamese era. Sledgehammer put this title on hold to work on MW3, and now work on Advanced Warfare.
Sledgehammer has told IGN more information about the title; it was internally called Fog of War and mixed Call of Duty with play style of Uncharted.
Set against a horrific Vietnam War backdrop, Fog of War was conceived as “Call of Duty with the play style of Uncharted,” Sledgehammer’s Michael Condrey told IGN. “It was really taking our passion for Call of Duty with our experience and expertise from Dead Space and bringing that together to offer fans a new Call of Duty way to play.”
Condrey explained that returning to Fog of War is still possible. “In our hearts, there’s probably a place for that game,” he said. “You never want to say in absolute terms that you wouldn’t go back to it.