We know what WWIII looked like. It was fought between 1945 and 1990. (Aprox)
The Soviet Union lost.
However, it was mostly fought in the Third World, so despite the fact that millions died and whole continents had their political and economic systems disrupted blighting the lives of possibly billions of people, most of "Us" never really saw it happening.
Of course, much of the problems in the world today are "Fallout" from this conflict. So its consequences will continue to rumble on for some considerable time.
The question is, will this result in a WWIV, and what will that be like?? :/