Book excerpt: North Korea's leaders have sought to dominate the Korean Peninsula since then failure to conquer the Republic of Korea (ROK) in tine Korean War. However, they have lacked the economic, political, and conventional military means to achieve that dominance, having instead come to rely on their nuclear weapon and ballistic missile programs, Today, North Korea's nuclear weapons pose an existential threat to the ROK, and they might soon pose a serious threat to the United States; even a few of them could cause millions of fatalities and serious casualties if detonated on ROK or U.S. cities. The major ROK and U.S. strategy to moderate this threat has been negotiating with North Korea to achieve denuclearization, but this effort has failed and seems likely to continue tailing. North Korean leader Kim Jong-un, despite committing to denuclearization, has continued his nuclear weapon buildup. The authors of this Perspective argue that there is a growing gap between North Korea's nuclear weapon threat and ROK and U.S. capabilities to defeat it. Because these capabilities will take years to develop, the allies must turn their attention to where the threat could be in the mid to late 2020s and identify strategies to counter it. Doing this will help establish a firm deterrent against North Korean nuclear weapon use. The authors conclude that North Korea will be most deterred if it knows that any nuclear weapon use will be disastrous for the regime-that these weapons are a liability, not an asset. Book jacket.