For soft targets (e.g. cities) an air burst would be used - but for hard targets a ground burst (or even penetration) would be used: https://en.wikipedia.org/

For soft targets (e.g. cities) an air burst would be used - but for hard targets a ground burst (or even penetration) would be used: https://en.wikipedia.org/wiki/Ground_burst https://en.wikipedia.org/wiki/Ground_burst Some weapons even allowed for "laydown delivery" where weapons would be on the ground for a bit before detonating: https://en.wikipedia.org/wiki/Laydown_delivery https://en.wikipedia.org/wiki/Laydown_delivery From what I recall, the really large weapons (10MT-25MT) were mainly intended, at least in the latter stages of the Cold War, to be used against hard targets.