A ground invasion would have killed more people. This is pretty well accepted by historians because it would have have to have proceeded by a firebombing of th

A ground invasion would have killed more people. This is pretty well accepted by historians because it would have have to have proceeded by a firebombing of the invasion target to make it even possible to land the marines on the shore. And then there would have been the very long, very deadly fight all the way to Tokyo, with many many many civilians dying along the way in addition to the soldiers. Also, Nagasaki is a cautionary tale about starting wars, and probably applies more to Japanese imperialism than American.