I've heard many different points of view on the subject ranging from there was no need since negotiation were being done, to it being the only way the Japanese would have surrendered but people on both sides seem to say the other side is lacking information. Could some of you just help lay down some facts?
Why don't you take a look at this thread and see if it answers your question. If it doesn't, ask a follow-up. There is no way to "prove or disprove" necessity, because "necessity" is an ill-defined concept here (there is nothing "necessary" in war, there are just various kinds of trade-offs, various different goals states and people are trying to accomplish). There were various alternatives on the table (other than "full-scale land invasion"), and whether or not you think they would have been better to pursue depends largely on interpretation and what you value in the outcome (there is no obvious, easy answer).