And even that is debatable. Japanese surrender came shortly after a quick succession of several events - the first bomb at Hiroshima, Soviet Union declaring war and invading continental Japanese land, the second bomb at Nagasaki, allies completely obliterating Japanese navy, and preparing to invade their home islands, etc.
Many argue that Japan would surrender even without the two nuclear bombs.
Can humans even have a real communist society? I suspect it would take a species without any individual self-preservation instinct, or individual greed, so that each member can fully serve the collective.