In the Dune universe, when a laser weapons hits a shield, both are destroyed in a nuclear explosion reaction.
So instead of building nuclear weapons, wouldn’t it be easier to tie a timer and a “parachute” to a laser gun and drop it from orbit onto your enemy’s city?
Is this mentioned in the book? I can’t recall.
It is, in the opening as well as (more briefly) when Duncan leaves his shield in the desert as a booby trap for the Harkonnen search parties.