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?
Also remember - no computers and that all space access is through the spacing guild or whatever it’s called.
So control/timing is difficult and you would have to persuade (bribe) the spacing guild to support you. (Or have someone suicidal enough to do it manually. Could be set up manually with a timer I guess?
Timer seems easy to do.