For over thirty years, the United States, South Korea, and other interested governments sought through negotiations to eliminate North Korea’s nuclear weapons capability. Although negotiations achieved some limited and temporary successes, they ultimately failed. Now the DPRK is engaged in a relentless effort to expand and diversify its nuclear and missile capabilities to the point where many observers believe it has shifted from a doctrine aimed at deterring coercion and attacks against North Korea to a more offensive nuclear strategy that envisions nuclear warfighting and would allow the North to pursue its own coercive agenda. Especially worrisome is the North’s stated willingness to use nuclear weapons preemptively if it believes its leadership is threatened and its emerging capability to threaten U.S. cities with nuclear attack to discourage the United States from coming to the defense of its Northeast Asian allies. This paper discusses progress North Korea has made in advancing its nuclear and missile capabilities, examines the shift in DPRK nuclear strategy that these advances have permitted and signaled, addresses key dangers posed by the DPRK’s nuclear and missile programs and the shift in its nuclear strategy, and outlines possible U.S.-ROK responses to the growing North Korean threat, including reinforcing the U.S. extended nuclear deterrent.