Let's say neither the Allies or the Axis would have began projects to create nuclear weapons, and the bombs dropped on Hiroshima and Nagasaki never existed and will continue to never exist throughout history.
How long would WWII have lasted without these WMD's, and how would joint war between the U.S, U.K, and U.S.S.R against Japan end? Would it be divided between them as seen with Germany? This is assuming that Japan had no chance of fighting back millions of allied soldiers and air raids.
Also, without nuclear weapons restraining the U.S and the Soviet Union from going to war for nearly five decades, would they have gone to war sometime in the 1950's or 60's due to tensions over the futures of Korea and Vietnam?