In June 2024, North Korea, which has developed robust nuclear capabilities, restored its Cold War-era alliance with Russia. This chapter examines regional power dynamics, particularly focusing on the nuclear balance in Northeast Asia, using the concept of the “line of nuclear deterrence (LND).” The northern triangle nations in Northeast Asia—Russia, China, and North Korea—have acquired more nuclear weapons than the United States and have established their respective LNDs, totaling three LNDs, while the southern triangle nations—the United States, South Korea, and Japan—rely on the single US LND. As a long-term strategy, the United States should consider increasing its nuclear arsenal to prevent further deterioration of the nuclear balance vis-à-vis the northern triangle. In the short term, the southern triangle could explore options such as sharing nuclear missiles in US nuclear submarines and deploying US nuclear weapons to Guam. If the situation worsens, the United States might need to consider redeploying its nuclear weapons to South Korea while pursuing the involvement of the United Kingdom and/or France in the nuclear balance in Northeast Asia.