You don’t need to crack the game. The original campaign is widely available for low prices, often during sales.
Circumventing DRM is illegal in many countries under digital copyright laws (such as the DMCA in the U.S.). While individual enforcement is rare, it’s still a violation. call+of+duty+world+at+war+single+player+crack+download+link
There are several legal ways to access "Call of Duty: World at War": You don’t need to crack the game