Reaffirming U.S. Nuclear Deterrence and a New Phase in the U.S.-Japan Alliance: The Strategic Significance of the Expanded Deterrence Dialogue in February 2026

On February 18, 2026, the U.S.-Japan Extended Deterrence Dialogue (EDD) held at the State Department in Washington, D.C. marked an important milestone in indicating a new strategic direction for the U.S.-Japan alliance under the Trump administration. During this dialogue, the United States reaffirmed its firm resolve to defend Japan using all defense capabilities, including nuclear forces, and expressed full support for Prime Minister Sanae Takai's policy of strengthening defense capabilities.

The Extended Deterrence Dialogue was co-chaired by representatives from the U.S. State Department and the Department of Defense, with delegations from the Joint Chiefs of Staff, Strategic Command, and Indo-Pacific Command participating. On the Japanese side, the Ministry of Foreign Affairs and the Ministry of Defense co-chaired, with participants from the Joint Staff Office also included. This multi-layered participation structure demonstrates that nuclear deterrence is not merely a diplomatic declaration but a strategic commitment closely linked to actual operational plans.

Particularly noteworthy in this dialogue was the shared serious concern between the two countries regarding China's rapid and opaque nuclear weapons buildup and nuclear testing, as well as Russia's historical non-compliance in arms control. The United States emphasized the necessity of multilateral strategic stability and arms control negotiations, while Japan welcomed the U.S. intention to achieve better agreements and underscored the importance of engaging Russia and China. This reflects the recognition that the bilateral arms control framework from the Cold War era can no longer address the current multipolar nuclear threat environment.

The two countries also discussed the progress of North Korea's (DPRK) nuclear and missile programs and reaffirmed their commitment to the complete denuclearization of the Korean Peninsula. However, in reality, North Korea's nuclear armament has become a fait accompli, and the goal of "complete denuclearization" appears to be positioned more as a long-term ideal, with a focus on deterrence and crisis management in the short term.

The landslide victory of the Takai administration in the elections signifies a clear national mandate for strengthening Japan's defense capabilities and taking on greater responsibility for maintaining peace in Asia. Prime Minister Takai, as the leader of the Liberal Democratic Party, has set forth a policy to enhance Japan's military power and play a more proactive role in regional security. While this direction could provide an opportunity for the United States to alleviate the burden of the alliance, experts caution that it should not be used as an excuse for retreating from deepening the alliance.

In fact, it has been confirmed that the U.S. nuclear posture and policy, along with Japan's expanded investment in conventional defense capabilities, play a crucial role in deterring aggression in the region and responding as necessary. Although Japan does not possess nuclear weapons, it is protected under the U.S. nuclear umbrella known as "extended deterrence." This framework not only strengthens Japan's security posture in the Indo-Pacific region but also clearly demonstrates the U.S. commitment to Japan's defense against competing powers such as China and Russia.

The delegations from both countries also discussed guidelines for extended deterrence, strategic messaging of the alliance, communication during crises, and enhancing coordination to support U.S. extended deterrence backed by Japan's defense capabilities. Regular tabletop exercises were also conducted to verify the coordination and response capabilities of both countries in actual crisis scenarios.

The most significant strategic implication of this Extended Deterrence Dialogue is that the U.S.-Japan alliance is deepening from a mere political partnership in peacetime to operational-level integration that anticipates actual responses, including nuclear use, in emergencies. As the military rise of China and the nuclear threat from North Korea become more pronounced, Japan's defense policy is effectively transitioning from "defensive defense" to "proactive defense." The increase in defense spending under the Takai administration, the possession of counterstrike capabilities, and close coordination with the U.S. nuclear posture reflect this new strategic reality.

However, this deepening of the alliance also carries significant risks. An increased reliance on the U.S. nuclear umbrella means that Japan will become more subordinate to U.S. strategic judgments. Additionally, as diplomatic tensions with China escalate, strengthening military alliances could further exacerbate regional security dilemmas. Reports that the Japanese government advised fishermen to avoid areas around the Senkaku Islands during the ongoing diplomatic crisis with China since the end of 2025 suggest a complex balance between strengthening military deterrence and actual crisis management.

The future challenge for the U.S.-Japan alliance will be to maintain the credibility of deterrence while preventing accidental escalation and leaving room for diplomatic resolution. Frameworks for regular strategic dialogues, such as the Extended Deterrence Dialogue, play an essential role in maintaining this difficult balance. The dialogue in February 2026 not only demonstrated that the alliance continues to adapt to a new strategic environment but also made it clear that Japan's security policy is at a historic turning point.