Hey Wayne! Nuclear weapons are pretty blunt to be effective defensive weapons. They have some deterence value, but when you start shooting them off in your own country as a defensive measure, they destroy more than conventional weapons would. And having nuclear weapons makes one's neighbors nervous and more likely to stage preemptive attacks to deter deployment of the nuclear. It could lead to a rather vicious cycle.
And shooting them off toward neighboring countries would not be construed by the neighbors as defensive.