We often hear these days that the North Korean nuclear weapons program is a failure of deterrence. It is not. DPRK’s nuke forces were developed for the same reasons ours exist: to deter another state from attacking it. (In particular, the US.) DPRK’s program is a confirmation of the concept of deterrence.
The concept of deterrence means a state has nuclear weapons so other states dare not attack. As such all states might aspire to develop a deterrent. Our ‘deterrence’ was never meant to prevent states form going nuclear, only to prevent them from attacking us.
Preventing other states from going nuclear was the purpose of the 1968 Non-Proliferation Treaty. The NPT deal was that non-nuclear weapons states would abstain from developing nuclear arsenals in exchange for a promise from the nuclear weapons states to negotiate in good faith to achieve genuine reductions and eventual abolition of nuclear arsenals. The nuclear weapons states have not done that. They still have 15000 nukes. That is the failure.
DPRK’s nuclear development isn’t down to a failure of deterrence but rather a failure of the nuclear weapons states to abide in good faith by the Non-Proliferation Treaty.