Well the potential loss of life as the Japanese fought tooth and nail on their homeland for survival is the classic justification for the use of the A-bombs, conveniently forgetting of course that it was also a mesage to Stallin, and that more Japanese cities would eventually have been targetted and it would probably never have been used in the WW2 European theatre, as to many whiteys would have been nuked! It certainly did present a finality, an unconditional surrender would have been much more difficult without it! Re potential huge loss of allied soldiers, surely the Japanese were close to defeat by this stage and had very little air defences left, yes the war would have been prolonged, but by how long? Of course Hiroshima would not have been preserved as it was (spared substantial prior conventional bombing) to be the laboratory for A-bombing and would have been destroyed by conventional B-52 bombing anyway!