> If you're going to bombard something for military purposes, the most effective technique involves using a very large number of nuclear weapons...
Only if you don't intend to occupy that land in the next 500 years, though. I'd imagine a tungsten telephone pole dropped from orbit has better deep-ground penetration than a nuke, too.
Sorry, this is a common misunderstanding. Modern nuclear weapons are generally very fuel efficient, while there are some short lived nucleotides that are brought on by the activation of elements exposed to the gamma ray flux during detonation, unless you actively try to make it 'dirty' (and thus long lived) you can go back to living there in a couple of months. The only cities which were atomically bombed are completely livable today (much less than 500 years).
The dangers of a large nuclear exchange are widespread climate change and economic disruptions brought about by entire supply chains being removed. Not 'wastelands' of bombed out cities too radioactive to visit.
Only if you don't intend to occupy that land in the next 500 years, though. I'd imagine a tungsten telephone pole dropped from orbit has better deep-ground penetration than a nuke, too.