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Japan’s Dilemma over JSDF Deployment to the Strait of Hormuz |
| March 20, 2026 |
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Kitae LEESenior Research Fellow, Sejong Institute | ktleekorea@sejong.org
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The U.S.–Israeli airstrikes on Iran in February 2026 presented Japan with a significant new challenge that simultaneously tested its Middle East diplomacy and the management of the U.S.–Japan alliance, serving as a catalyst for a comprehensive reassessment of Japan’s overall foreign strategy. Beyond a localized conflict, the airstrikes carry the potential to generate far-reaching repercussions for global energy supply chains and the international security order, and are therefore perceived as a direct threat to the Japanese economy, which is heavily dependent on energy imports.
Without explicitly condemning the U.S.–Israeli airstrikes, the Takaichi government reaffirmed its longstanding position that Iran’s development of nuclear weapons is unacceptable, thereby seeking a highly calibrated and nuanced balance between a pragmatic posture that prioritizes U.S.–Japan alliance cohesion and a principled stance grounded in adherence to international law and stability in the Middle East. This approach reflects a strategic calculation aimed at demonstrating steadfast support for its ally without undermining Japan’s long-standing identity as a “peace-oriented state,” while simultaneously managing the dual pressures of domestic and international public opinion. In other words, Japan is further consolidating a dual-track strategy between the stable strengthening of the U.S.–Japan alliance and the effective securing of energy security, while strategically maintaining a degree of ambiguity to avoid unnecessary antagonism in its Middle East diplomacy. Japan’s strategy should be understood not as an improvised response, but as a comprehensive approach aimed at redefining its role in the evolving international order while minimizing long-term security and economic risks.
The dilemma Japan faces is directly tied to the fundamental question of how to recalibrate and reinterpret the image of an “honest broker” that the Abe Shinzo (安倍晋三) administration cultivated over many years in the Middle East during the 2010s. At the same time, it is closely linked to the practical challenge of how to apply and operationalize the two key legal concepts introduced under Japan’s 2015 security legislation, namely the “existential crisis situation” and the “important influence situation,” in real-world contingencies. During the Abe administration, Japan sought to elevate its standing as an autonomous diplomatic actor on the international stage by attempting to mediate between the United States and Iran amid heightened tensions in the Strait of Hormuz. However, the current airstrikes on Iran have become a catalyst for a fundamental reassessment of the “Abe legacy.”
The existential crisis situation refers to circumstances involving a direct threat to Japan’s survival, while the important influence situation encompasses a broader category of indirect contingencies affecting Japan’s security environment. Whether the instability in the Strait of Hormuz resulting from the airstrikes on Iran, and the potential disruption of energy supplies, including crude oil, could qualify as an important influence situation has sparked intense debate within Japan. In particular, since Prime Minister Takaichi took office in October 2025, the emphasis on the U.S.–Japan alliance as the cornerstone of national security has been further reinforced. Japan must now establish clear criteria for the level of military support it will provide to the United States to reinforce the alliance.
In doing so, it faces a multilayered and complex policy dilemma regarding how to reconcile the pacifist principles of Article 9 of the Constitution, anti-war sentiment in domestic public opinion, the vulnerability of energy security stemming from dependence on Middle Eastern crude oil, and long-term economic and diplomatic relations with major regional producers such as Saudi Arabia and the UAE. The Takaichi government appears likely to employ a dual-track approach of diplomatic mediation and limited rear-area support in order to navigate this multilayered dilemma. This approach is expected to lead to a reinterpretation of Japan’s posture of “proactive contribution to peace” tailored to the Middle Eastern context. -
A review of Japan’s Iran policy and broader Middle East diplomacy during the Abe administration in the 2010s clearly illustrates that Japan sought to position itself not merely as a follower within the U.S.–Japan alliance, but as a diplomatic actor capable of exercising a degree of autonomy and initiative on the international stage. Prime Minister Abe directly conveyed to President Trump, during his official visit to Tokyo in 2019, Japan’s willingness to mediate on the Iran issue, thereby attempting proactive engagement by leveraging his personal relationship with the U.S. president. In June of the same year, Abe visited Iran, the first sitting Japanese prime minister to do so in 41 years, and held bilateral talks with President Hassan Rouhani, thereby formally assuming the role of facilitator of de-escalation amid heightened tensions between the United States and Iran. The Japanese government at the time actively pursued “mediation diplomacy” on the basis of its comparatively stable and favorable relations with Iran, while maintaining close ties with the United States. This clearly reflected a combination of Japan’s practical interests as an energy-dependent nation heavily reliant on crude oil imports through the Strait of Hormuz and the diplomatic ambition central to Abe’s foreign policy of positioning Japan as a “global player.”
However, within the structural constraint that security in the Strait of Hormuz represents a critical lifeline and strategic vulnerability for the Japanese economy, the Abe administration’s mediation efforts ultimately revealed clear limitations in alleviating the structural antagonism between the United States and Iran. There is also a contrasting assessment that Japan’s role remained confined to the parameters set by U.S. Middle East policy. Nevertheless, the experience and initiatives of the Abe era stand as a valuable legacy, demonstrating that Japan consistently sought to enhance its presence in the international community through “non-military contributions” and “diplomatic mediation” in the Middle East. These efforts were fundamentally premised on the stable and robust maintenance of the U.S.–Japan alliance, as well as on balanced and pragmatic relations with key regional actors, including Iran. -
The U.S. attack on Iran in 2026 has become a decisive turning point that tests the Abe-era legacy and prompts a fundamental reassessment of it, and is likely to serve as a critical juncture for redefining Japan’s Middle East diplomatic paradigm. Through statements by Foreign Minister Motegi Toshimitsu (茂木敏充) and other channels, the Japanese government has repeatedly reaffirmed its firm and longstanding position that Iran’s development of nuclear weapons is unacceptable. This reflects a clear intention to maximize diplomatic flexibility, as Japan adopts a strategy of “ambiguity,” refraining from explicitly expressing either support or criticism regarding the military actions of the United States and Israel.
Conservative-leaning media outlets in Japan have interpreted the government’s stance as reflecting the prioritization of U.S.–Japan alliance cohesion and a careful effort to accommodate President Trump ahead of Prime Minister Takaichi’s visit to the United States. They point to a deliberate and calculated posture in which Japan calls for early de-escalation while seeking to avoid any disruption to its strategic relationship with the United States. In contrast, some opposition parties and progressive media outlets have strongly taken issue with the fact that the United States and Israel launched unilateral military action without a UN Security Council resolution. They express concern over potential violations of international law, the deepening of long-term instability in the Middle East, and disruption to global energy markets. Accordingly, they have consistently criticized the Japanese government for failing to publicly articulate a principled and unambiguous position grounded in international law and UN-centered multilateralism.
As such, within Japan, competing interests and values, centered on the U.S.–Japan alliance, adherence to international norms, the urgency of energy security, and the diversification of Middle East diplomacy, are coming into sharp conflict. This is translating into a full-fledged policy debate over the form and extent to which Japan may become involved in future U.S. military operations, as well as how the resulting domestic and international risks are to be managed.
The most central and contentious issue to have emerged in this process is the application of the two legal concepts introduced under Japan’s 2015 security legislation: the “existential crisis situation” and the “important influence situation.” Whether these concepts are applied in practice is expected to serve as a watershed in determining the direction of Japan’s security policy. The “existential crisis situation” refers to circumstances in which an armed attack against a country or region in a close relationship with Japan gives rise to a clear and imminent danger that Japan’s survival is threatened and the lives and freedoms of its people are fundamentally undermined. In such circumstances, Japan would find itself in an unprecedented situation in which the exercise of the right of collective self-defense in a limited form under its constitutional framework is legally permitted. By contrast, the “important influence situation” refers to circumstances in which developments in areas surrounding Japan have an important influence on Japan’s peace and security. It provides a flexible legal framework under which rear-area support, logistical supply, medical assistance, and other forms of support for the armed forces of the United States and other countries become broadly permissible, even in the absence of a direct attack on Japan.
The domestic debate in Japan surrounding the U.S. attack on Iran is closely intertwined with the direct and indirect implications of the crisis for Japan’s energy security and the safety of its sea lines of communication (SLOCs), as well as the scope and limits of the specific support Japan can provide to U.S. forces. Specifically, detailed legal and policy deliberations are actively taking place both within and outside the government over whether mine-clearing operations on the high seas, real-time intelligence sharing, transport, and logistical support can be immediately implemented under an “important influence situation,” and whether, in the event that Iranian retaliatory strikes directly threaten the safety of Japanese merchant vessels or Japanese nationals overseas, the situation could be elevated to an “existential crisis situation.” -
It is also worth noting that Japan’s potential deployment of the JSDF to the Strait of Hormuz is characterized by three more specific dilemmas. First, a prerequisite for justifying a JSDF deployment is that the U.S. attack on Iran must not be formally defined as a violation of international law. The Japanese government’s deliberate maintenance of ambiguity to date regarding whether the military actions of the United States and Israel constitute a violation of international law reflects a calculated effort to preserve diplomatic space. However, once Japan officially decides to deploy the JSDF, it would, in effect, be acknowledging that U.S. operations constitute a permissible measure under international law. This could constrain Japan’s position in UN deliberations and in its broader Middle East diplomacy. Ultimately, the Japanese government would face pressure to clarify that the U.S. attack on Iran does not constitute a prohibited preemptive strike under international law and is not a violation of international law.
Second, the question of whether to deploy the JSDF is directly tied to the challenge of balancing the strengthening of the U.S.–Japan alliance with Japan’s Middle East diplomacy, particularly its relations with Iran. The Japanese government could opt for a deployment centered on non-combat missions, including rear-area support, intelligence provision, mine-clearing, and patrol and surveillance activities, under the banner of ensuring the safety of the Strait of Hormuz, thereby demonstrating alliance solidarity. However, given Japan’s longstanding economic and diplomatic relations with Iran, it is highly likely that Japan will seek to avoid, to the greatest extent possible, direct involvement in combat operations or offensive missions.
Third, the issue is closely linked to Article 9 of the Constitution and the debate over its revision. Japan has gradually expanded JSDF overseas deployments and international contributions with an eye toward revising Article 9 of the Constitution or making equivalent changes to its security policy. A Hormuz deployment also offers strategic incentives to reinforce Japan’s image as a responsible ally making meaningful “international contributions.” However, if deployed JSDF forces were to come under attack during operations, or, in the worst case, if casualties were to occur, domestic public opinion in Japan would likely turn sharply critical of overseas deployments. This could also intensify resistance to both the expansion of the JSDF’s role and the broader debate over constitutional revision.
The Takaichi government, which has constitutional revision as a key objective, therefore faces a structural constraint. It must balance its strategic goals of strengthening the U.S.–Japan alliance and expanding international contributions with cautious domestic political calculations regarding the potential backlash from JSDF casualties. Under these conditions, the government is likely to favor a risk-management approach centered on phased and limited deployment options.
At the current stage, the Japanese government remains reluctant to formally designate the U.S. attack on Iran as an “existential crisis situation,” a position that appears to reflect a calculated assessment of the associated political and legal risks. While the Takaichi government has placed the strengthening of the U.S.–Japan alliance at the top of its national security agenda, it would be difficult to designate the Iran attack as an existential crisis for Japan unless it escalates into a direct and unambiguous armed attack on Japanese territory or vessels. Given the strong backlash from domestic anti-war sentiment and the critical view of the international community, such a designation would impose significant political and legal costs.
Over the longer term, Japan may internally explore recognition of an “important influence situation,” citing as its primary basis the sustained escalation of tensions in the Strait of Hormuz and surrounding waters and the potential and tangible impact on the Japanese economy. Japan may also adopt phased and incremental response options, including expanding the scope of rear-area support for U.S. forces, strengthening the Maritime Self-Defense Force’s reconnaissance, intelligence-gathering, and patrol and surveillance activities, and deploying the JSDF to protect Japanese vessels and nationals. In such a scenario, the Japanese government could present a logical framework to the effect that “the rapidly shifting and unstable situation in the Middle East is having a significant and sustained impact on Japan’s peace and national security.” By focusing on rear-area support while excluding the full invocation of the right of collective self-defense or direct participation in combat operations, Japan could seek an effective compromise between alliance demands and domestic constitutional and public opinion constraints. -
Following the U.S. attack on Iran, the Trump administration actively sought multifaceted and robust contributions from its allies, including political support, military rear-area support, and financial burden-sharing, in pursuit of its long-term objectives of eliminating Iran’s nuclear and missile capabilities and countering its regional hegemonic ambitions. President Trump called on five countries, China, France, Japan, South Korea, and the United Kingdom, to participate in a coordinated response to keep the Strait of Hormuz open.
The U.S.–Japan summit between President Trump and Prime Minister Takaichi, held on March 19, 2026, served as a decisive turning point linking the intense security and diplomatic debate within Japan to concrete and substantive policy choices and agreements. It marked a critical juncture at which Japan’s response strategy toward the Middle East situation was formally articulated on the international stage. At the U.S.–Japan summit, President Trump stated that Japan should step up and play a greater role, unlike NATO member states that have taken a more cautious stance toward the war against Iran. He argued that Japan must act, given that it imports more than 90 percent of its oil through the Strait of Hormuz and the fact that it is the United States that is defending the Strait. In response, Prime Minister Takaichi condemned Iran’s actions in attacking surrounding areas and effectively blockading the Strait of Hormuz, and expressed clear opposition to Iran’s nuclear development, but refrained from specifying Japan’s role. She explained to President Trump the constraints imposed by Article 9 of the Constitution, which permanently renounces the use of force as a means of settling international disputes, as well as relevant security legislation, and proposed a security cooperation framework centered on the co-production of missiles with the United States.
In other words, Japan effectively rejected the deployment of the JSDF while hostilities remain ongoing, invoking the principled constraints embodied in its peace constitution. Looking ahead, should the conflict come to an end and the three dilemmas be resolved, Japan is expected to pursue the necessary legal preparations and domestic support to enable a more active role. This may include non-combat contributions such as mine-clearing, logistical transport, and intelligence sharing in the Strait of Hormuz, participation in post-conflict reconstruction in the Middle East, expanded humanitarian assistance, and the diversification of economic cooperation initiatives. -
Japan’s cautious approach carries significant policy implications and lessons for South Korea, which must strategically account for Northeast Asian security scenarios such as a Taiwan Strait contingency or a Korean Peninsula crisis. It also provides important insights for assessing the future of ROK–U.S.–Japan security cooperation. In November 2025, Prime Minister Takaichi stated during a session of the National Diet that an armed conflict in the Taiwan Strait could constitute an “existential crisis situation” for Japan, thereby publicly articulating a worst-case scenario envisioned under Japan’s security legislation. The remarks were widely interpreted as a hardline statement symbolizing Japan’s expanded regional security role. However, Prime Minister Takaichi subsequently refused to retract the statement while expressing limited “reflection” on her choice of words. This reflects an approach of maintaining strategic ambiguity, setting a high threshold for the application of legal concepts while preserving room for political and diplomatic interpretation, thereby securing flexibility in response.
Ultimately, the determination and application of an “existential crisis situation” and an “important influence situation” are inherently political decisions, made on a case-by-case basis through the Japanese government’s comprehensive assessment of domestic anti-war sentiment, the strategic expectations of its ally, the United States, and its complex relationships with neighboring states, including China, South Korea, and North Korea. How Japan operationalizes and interprets these legal concepts in the Iran crisis will serve as a valuable precedent for anticipating their application in future contingencies, including a Taiwan Strait crisis or instability on the Korean Peninsula.
At the same time, despite its hardline declaratory statements on Taiwan-related scenarios, Japan is likely to maintain a degree of strategic ambiguity and caution in actual contingencies, taking into account diplomatic relations with neighboring states, the risk of escalation with China, and the potential impact on its own territory and nationals. This is evident in Japan’s current cautious and restrained posture in response to the Iran crisis.
From South Korea’s perspective, what matters most is not to take Japan’s legal concepts or unilateral declaratory statements at face value or place undue trust in them, but to closely monitor and analyze the specific political and strategic calculations and priorities that the Japanese government applies in actual international contingencies. In the Iran crisis, Japan has confined itself to a limited response, while prioritizing the strengthening of the U.S.–Japan alliance and simultaneously weighing its pragmatic relations with Middle Eastern oil-producing states, the pressing realities of energy security, adherence to international law, and strong domestic public opinion. This strongly suggests that, in scenarios such as a Taiwan contingency or a Korean Peninsula crisis, Japan is likely to maintain a combination of strategic ambiguity and caution as it balances alliance expectations, regional stability, and its own core interests.
South Korea, for its part, should clearly articulate a consistent position grounded in international law, international norms, and the principles of the ROK–U.S. alliance, while deliberately maintaining a degree of strategic ambiguity that avoids directly linking specific contingencies to immediate military intervention or alignment with a particular bloc. Such a prudent approach would strengthen South Korea’s diplomatic flexibility. In other words, it is necessary to assess Japan’s evolving role and its limitations in a sober and objective manner within the firm framework of the ROK–U.S. alliance and the practical framework of ROK–U.S.–Japan security cooperation. At the same time, South Korea should conduct sustained and detailed analysis of the legal concepts embedded in Japan’s security legislation and its political decision-making structures in order to design more flexible and multidimensional policy options.
Closely tracking and analyzing Japan’s decision-making processes, limitations, and strategic calculations, as reflected in its management of Iran diplomacy and the strengthening of the U.S.–Japan alliance, is a fundamental prerequisite for South Korea. Such efforts are essential for anticipating potential contingencies in Northeast Asia, including scenarios in the Taiwan Strait and on the Korean Peninsula, as well as for expanding its strategic space and maximizing its international influence.
| Japan’s Former Prime Minister Abe and His Middle East Diplomatic Legacy
| Japan’s Strategic Ambiguity and the Intensification of Domestic Security Debate
| Three Dilemmas Surrounding the Deployment of the JSDF to the Strait of Hormuz
| The March U.S.–Japan Summit and Japan’s Rejection of the Deployment Request
| Implications and Policy Recommendations for South Korea
※ The contents published on 'Sejong Focus' are personal opinions of the author and do not represent the official views of Sejong Institue
