J. Robert Oppenheimer believed that fifty atomic bombs would be needed to defeat Japan. Scientists and military figures considered them as nothing more than large-scale conventional weapons. Each atomic bomb could accomplish what took a week with conventional bombing and, as the radiation effect was still unknown, there seemed no reason to withhold using them. Members of the 509th were informed that their stay on Tinian would be a long one.
http://www.atomicheritage.org/location/tinian-island
Now I am become Death the destroyer of worlds.