Blockbusters.
I recall that the RAF dropped 11-ton
"blockbusters" from Lancaster bombers
near the end of WWII.
Such bombs would generate such powerful overpressure on the ground and rock beneath, that it wouldn't be a good idea to live in caves beneath the bomb-drop target, "ground zero"...otherwise, you might
find yourself buried alive, or sealed in that cave.
A B-52 has the engine-power to
carry two such devices into the air,
to their targets, thousands of miles away.
Jake