[RayChuang88]

They were able to rebuild both Hiroshima and Nagasaki because the bombs were detonated several thousand feet off the ground for maximum blast effect. As such, it meant the soil at Ground Zero had only a very small increase in radioactive products, and that meant both cities undergo rebuilding in a few years.

If the bombs had detonated very close to the ground (in effect a ground burst), the soil around Ground Zero would become extremely radioactive, and it would have taken several decades to ensure the radiation is low enough to ensure safe rebuilding. That's why it's still a bit dangerous to walk around the Nevada Test Site in the areas where they did the test explosions, since the bombs were detonated on towers only a few hundred feet off the ground. And there is much debate whether we could even safely have people living on Eniwetak Island even though the island was supposedly cleaned up by 1980.

[Jeff Head]

The point is...for most attack, short of hitting embedded bunkers, that is how the nuclear missiles would be used.