Actually the Japanese had already offered a conditional surrender,
You are correct -- a 'conditional' surrender.
The condition was that the Allies simply stop the fighting, go home, and leave Japan to it's own devices.
With intelligence telling the Allied commanders that Japan still had more than four million men under arms, thousands of planes, hundreds of ships, and a still unfulfilled need for natural resources which it did not possess, what is the logical scenario?
Simply this. The Allies, tired and economically spent after up to thirteen years of Japanese conquest, withdraw, disband their armed forces, revert to a peace time economy, and resume normal life.
A few years down the road, Japan, having rebuilt its navy, developed new weapons and aircraft, expanded its armed forces, decides to resume its aggressive posture and begins to, once again, invade its neighbors. Now it is the strongest military force on earth because the Allies have "beat their swords into plowshares", as it were.
This was the risk that the Allies viewed and no one wanted to look forward to World War III.
The only way to mitigate against this scenario was to occupy Japan and ensure that its armed forces and military production capabilities were neutralized.
Hence 'unconditional' surrender, which included full occupation was the only reasonable course for the Allies. Since the Japanese would not voluntarily accept occupation, the war continued.
The Japanese were committed to defend the home islands to the death, as they had the outer islands of Iwo Jima and Okinawa where even Japanese civilians fought to the death or committed suicide rather than surrender.
The Allies estimated that the combined Japanese and Allied death toll resulting from an invasion of the home islands would run into the several of millions over the course of several years. They saw the A-bomb as a way to bring the war to an immediate end, which it did with a saving of millions of lives.
When docking a dog, is it less painful to cut off the tail an inch at a time? Certainly not. One whack, in the right place, and it's over.
and Jesus didn't really go on about self defence did he, meanwhile God said it was alright to stone adulterers to death
I don't understand the relevance here. As I recall, Christ didn't challenge Mosaic law. He simply admonished, in it's being carried out that, "Let he among you who is without sin cast the first stone."
Had there been a hypocrite or a sinless person present, the outcome would have been different for the adulterous woman.