Japan didn't surrender because of anything the US did, but because Russia declared war on them (two days after Hiroshima and a day before Nagasaki). The US may

Japan didn't surrender because of anything the US did, but because Russia declared war on them (two days after Hiroshima and a day before Nagasaki). The US may just as well have dropped 10 more nukes and it wouldn't have changed anything. The Japanese didn't care whether it took a 1.000 bombs to destroy a city or a single one. Even more so, since they didn't know anything about the radioactive fallout and long-term effects. To them, it was just a bigger bomb.