Japan-US Security Challenges from the Atlantic to the Pacific

Japan Forward

13 hours ago

Hudson Institute's Japan Chair challenges conventional international relations thinking by integrating a wide range of perspectives toward beyond-the-horizon policy issues. JAPAN Forward is pleased to amplify the voices of its experts by sharing this report with our readers.
The world's strategic focus is today centered on regions far distant from the Indo-Pacific in the Middle East, on Israel's June 13 preemptive strike on Iran's nuclear infrastructure, joined by the United States on June 21. And on Israel's continuing efforts to root out Hamas in Gaza, in addition to Russia's ongoing aggression against Ukraine.
Yet, the challenges to stability and security in the Indo-Pacific have only intensified. At the time of Russia's invasion of Ukraine, then-Prime Minister Fumio Kishida cautioned lest Ukraine preview the future of East Asia. His concerns are even more relevant today.
On the Korean Peninsula, Kim Jong Un, now with Vladimir Putin's support, has continued to advance North Korea's nuclear and missile programs, daily increasing the threat posed to the security of the Republic of Korea, Japan, and the United States. In turn, Seoul, Tokyo, and Washington have moved to enhance alliance-based trilateral security and intelligence cooperation.
Meanwhile, China has intensified and expanded the People's Liberation Army's (PLA) threatening military exercises that simulate an attack on or blockade of Taiwan. US Secretary of Defense Pete Hegseth recently reminded the audience at the Shangri-la Dialogue that Xi Jinping has ordered the PLA to be prepared to invade Taiwan by 2027. The Chinese naval aircraft carrier "Shandong" sails. China Central Television Online showed this on July 2 as part of a training exercise around Taiwan. (via CCTV Online via Kyodo) .
A Taiwan contingency could present Japan with security-related challenges for the defense of Japan as well as the alliance. As former Prime Minister Shinzo Abe observed, "A Taiwan contingency is a contingency for Japan …it is also a contingency for the Japan-US Alliance."
And a decision by the US to engage in a Taiwan contingency is, as Abe noted, likely also to involve Japan.
Former diplomats, defense officials, foreign policy and security analysts have recognized Japan's likely involvement. Liberal Democratic Party Vice President Taro Aso has expressed his view that a Taiwan contingency would likely present Japan with a "survival-threatening situation," which would evoke a response under Japan's Peace and Security legislation.
Articles by Admiral Yoji Koda, former commander of the Japan Maritime Self-Defense Force and Nobukatsu Kanehara, former assistant chief cabinet secretary, have addressed issues related to the defense of Japan and the alliance. Keio University professor Ken Jimbo wrote that a Chinese invasion of Taiwan would inevitably lead to a joint Japan-US response.
Meanwhile, Japan's think tanks, the Japan Forum for Strategic Studies, the Sasakawa Peace Foundation, and the Research Institute for Peace and Security have convened study groups and conferences focused on a Taiwan contingency.
Unfortunately, the articles and conference reports have all too quickly faded from public debate and the political forum, left by Japan's political leaders to backroom discussions and foreign ministry and Ministry of Defense bureaucrats. It's a political exercise of whistling past the policy graveyard.
Yet, within Japan and across the alliance, diplomats and defense planners have increasingly focused on a Taiwan contingency. The joint statement issued at the March 2016 Security Consultative Meeting, for the first time, referred to the importance of peace and stability in the Taiwan Strait for Japan and United States' security interests. Subsequent joint statements have reiterated their importance.
Over the past several years, the media have reported Japan-US agreement on operational plans in the event of a Taiwan contingency. Also, Japanese and US forces have conducted joint exercises focused on China as a hypothetical enemy.
Today, Japan's 2016 Peace and Security laws provide the legal framework for Tokyo's response to a Taiwan contingency.
The laws establish distinct operational commitments under distinct security situations. For example, an "Important Influence Situation" is defined as "having an important influence on Japan's peace and security that could lead to a direct armed attack on Japan itself if left unattended." The laws would enable the SDF to provide rear-area support to United States forces engaged in activities aimed at securing the objectives of the security treaty. They do not allow the provision of weaponry, but they support the provision of ammunition, refueling, and aircraft maintenance in support of combat operations.
LDP's Taro Aso referred to an "armed attack, anticipated armed attack, or survival-threatening situation" in his remarks on Taiwan. He added that Japan could use force in response to "an armed attack against a foreign country that is in a close relationship with Japan, which, as a result, threatens Japan's survival." An attack by the PLA on US forces engaged in a Taiwan contingency could bring about a survival-threatening situation for Japan.
Looking ahead, what is to be done?
For starters:
In both Tokyo and Washington, policymakers must consider and work through various scenarios involving a potential United States decision to engage in a Taiwan contingency. This would not only enhance deterrence but also serve to develop an alliance-based response across a broad spectrum of potential conflict and escalatory scenarios. Joint military exercises toward this end are critical.
This will also require policymakers in Tokyo and Washington to work closely to align their countries' respective national interests with respect to China, Taiwan, and a Taiwan contingency.
At the same time, diplomats and defense officials should work to coordinate respective national policy decision-making processes.
Because a Taiwan contingency could occur unexpectedly, time would be of the essence in developing critical policy responses. A situation in which the United States moves to engage in a Taiwan contingency while the Diet debates its response and what support it can provide its ally should be avoided at all costs.
Finally, political leaders in Japan and the United States need to bring the complexities and potential consequences of a Taiwan contingency into the public forum. This is critical to ensure a sustainable, long-term political foundation for future policy decisions. Unfortunately, this remains a work in progress.
And 2027 is only 18 months away.
Author: James J Przystup
Senior Fellow, Japan Chair, The Hudson Institute
The Hudson Institute's Hudson Chair contributed this report on July 4, 2025. Learn more about Hudson on its home and Japan Chair pages.