Air versus ground is a major factor. In the early days, we targeted whole cities with air bursts, relying on a WWII mentality to warfare. Then, as we gained the

Air versus ground is a major factor. In the early days, we targeted whole cities with air bursts, relying on a WWII mentality to warfare. Then, as we gained the ability to target specific military installations, which simultaneously became more hardened, we moved to high ground bursts, then impact bursts, which pretty much means a huge mess. We can easily dig a hole in the ground 60 meters deep, but that means a staggering amount of debris high in the air, some of which will be radioactive.