User blog comment:Crazy sam10/Infinity Ward explains leaving Modern Warfare series/@comment-186.205.239.234-20130531211210/@comment-3967954-20130602210245

Other than "No Russian", MW2 did nothing to warrant the 18 certificate. The fact that IW have a sort of intolerance of harsh language for the most part and their refusal to add any strong gore in their games certianly is a contrast to Treyarch's gritty depiction of WWII, which saw the slaughtering of PoWs, intense violence and an f-bomb in every other sentence. So quite how WaW managed to escape the 18 certificate is way beyond me.