There are a few things people forget when they say we shouldn't have dropped the bomb and used a blockade. And that is the fact that Russia had declared war on japan and were SWIFTLY owning them in manchuria, they were still pissed about their loss to japan in the previous war of 1905 i think it was (not sure about the year) enter E/W Germany all over again. Another thing is invasion of japan would've meant civillians die anyway , they were ARMING anyone who could fight to fight that meant young boys and probably girls at this point. ANOTHER thing is that even AFTER we dropped the bomb on Japan there were STILL some army generals ready to fight to the very last man Hirohito finally grew some balls. Also japan was EXTREMELY close to prolonging the war by deystroying the panama canal because they developed a submarine air craft carrier and were half way there before being called back to defend Okinawa in suicide attacks. Furthermore, japan was extremely close to getting plutonium from Germany for the manufacturing of dirty bombs that were going to cover OUR west coast, they were fully prepared to deploy nuclear weapons on us and bring us to the barganing table. Invasion would've meant a macedonian victory for the Allies.
The reason surrender was unconditional is simple, the acting government in the country was the result of a military coup. A coup inspired by an authors book no less(or we'll say put them over the top), the phone call made to the author after this coup was carried out informing him that the japan he spoke of was realized was classic to say the least, all he could muster up as a response is.."huh". The same pattern that happens in all countries that have military coups really, opposition, thinkers, intelligent people are killed, and general public are lead as sheep. Why the hell would anyone negotiate with THAT government, if the US was defeated in a war tomorrow who would negotiate with Bush...seriously.