This chapter introduces the concepts of “alliance correctness” and “alliance frankness” and evaluates the effectiveness of U.S. nuclear extended deterrence (NED), providing both theoretical and policy insights. In particular, it compares the NED policies of the Trump and Biden administrations toward South Korea to assess whether their alliance commitments were substantive or largely symbolic. The analysis reveals that, while the two administrations employed different approaches—with the Trump administration representing “alliance frankness” and the Biden administration representing “alliance correctness”—their actual levels of NED posture against North Korea were similar. Although South Koreans exhibited greater confidence in the Biden administration, its efforts primarily focused on dissuading South Korea from pursuing nuclear armament rather than meaningfully enhancing the practical nuclear deterrent against North Korean threats. In this regard, it is more appropriate to evaluate U.S. alliance policy based on concrete efforts to strengthen actual deterrence postures for combined war deterrence, rather than on rhetorical commitments. Accordingly, the United States should prioritize practical measures to strengthen its NED posture toward South Korea, including the forward deployment of U.S. nuclear weapons closer to the Korean Peninsula, instead of merely issuing strong verbal commitments.