See, the main difference is the scale of the destruction. WW2 exactly ended because it escalated to really horrendous levels. (If the Japanese or Germans got the nuke first, we'd be in a very different world now.)
WWI culminated in development of chemical weapons. They were used in wartime, assessed, and stockpiled. But everybody was scared of ever using them again. Chemical weapons were not used in WWII.
The same thing happened with nuclear weapons in WWII. They were used, evaluated, and then stockpiled. But everybody was scared of ever using them again, and they weren't. Nuclear weapons most probably will not be used in WWIII.
