The arguments against a demo were many. The Japs moved American prisoners to expected bombing locations so prewarning was a bad idea. They didnt have enough uranium for many bombs so couldn't waste it on a demo. They wanted to end the war before the Soviets participated more and had a claim to Asia. Actually the jap general's and military wanted to continue even after the second bomb. It was the emperor who shut them down.its unclear if hecould have done that after just one bomb. the Japanese generals were as careless about life as Churchill. Remember tokyohad already been fire bombed worsethan nuked and the Japanese hadn't given up.it was the knowledgethat the usa could wipe out Japan without landing a man on the island that made the emperor stop his military men. Only an unknown weapon like a nuke could effect that change in mindset.