If Modern Warfare hadn't been as hugely successful as it was back in 2007, the Call of Duty series was going to take a very path. Devil's Brigade was Activision's back-up plan if MW had flopped, a third person shooter that would have explored a group of historically inspired American and Canadian soldiers, members of the short-lived but infamous Devil's Brigade.
The developers of the game had planned to capture the essence of the legend around the unit, offering against-all-odds gameplay and super-humanly athletic playable characters. The game would have been slower than what we recognise as Call of Duty, relying on stealth takedowns and strategic planning.
It's very different from what we know and begrudgingly love and it sounds like the sort of thing that people will say "this is exactly what I want from a Call of Duty game." The article that details what the game could have been is very interesting and I definitely suggest a read if you have half an hour.
Who knows? A postive reaction might make Activision re-examine their decision.