Co
World At War is the 5th game in the series and it's a lot easier to say CoD5 instead of Co
WaW. Same with the next game its gonna be easier to call it CoD6 instead of Co
Modern Warfare 2. (or whatever its gonna be called cause I'm not sure if that is the official name, it could just be a code name or what people are calling it now until IW releases the official name)