We already have hundreds (thousands?) of Mt devices. A handful of Gt devices is not going to change anything as regards humanity's threat to itself.
In fact I believe that anything over the low tens of Mt is considered impractical for military use.
In fact I believe that anything over the low tens of Mt is considered impractical for military use.
Agreed, a big device doesn't really alter the balance of power, which is why both the Americans and Soviets abandoned the path of bigger and bigger devices by 1962, leaving lots of engineering possibilities on the table to instead focus on miniaturization.