On Wednesday, Sanae Takaichi sits across from Donald Trump in Washington. The official agenda is trade and investment. The real subject is the Strait of Hormuz.
Trump has publicly called on Japan, along with China, France, South Korea, and the UK, to send warships to secure the strait. Takaichi has told parliament that “we have not made any decisions whatsoever about dispatching escort ships.” The LDP’s policy chief has described the hurdles as “high”.
What neither side has said publicly is the uncomfortable truth at the centre of this conversation: Japan possesses the one military capability that the coalition needs most, and that the US Navy no longer has.
The capability no one is talking about
The problem in the Strait of Hormuz is no longer missiles or drones. It is mines. Iran has begun laying mines in the strait, and the US Navy sank 16 minelayers in a single engagement. But mines already in the water stay in the water. They are indiscriminate, persistent, and cheap. A single mine strike on a supertanker does not just destroy a ship; it renders the strait uninsurable. Without insurance, commercial vessels will not transit. Without transit, the oil does not flow.
The US Navy retired its four dedicated Avenger-class mine countermeasures vessels from the Persian Gulf in September 2025. Their replacement, the Littoral Combat Ship’s mine warfare module, has underperformed. In the most recent joint mine warfare exercise with Japan (MINEX 1JA, February 2026), the US contributed staff officers and explosive ordnance disposal divers. No dedicated mine countermeasures ships.
The asymmetry is not subtle. Nor is the irony: the JMSDF is recognised as a military force under international law, yet it cannot sail to Hormuz because of a constitution written by the United States.
Arguably the best in the world
The JMSDF’s mine countermeasures capability is not merely good. Multiple sources describe it in terms that no other navy receives.
James Auer, a former US Department of Defense specialist on Japan, argued in 1991 that “the best and most skilled minesweepers in the world belong to the JMSDF.” A detailed analysis by Random Japan Academy, drawing on operational history and fleet composition, concluded that “it is fair to evaluate the JMSDF’s mine warfare capability as arguably world’s best, especially in the minesweeping field.” Naval News has described minesweeping as “a specialty of the country.”
This did not happen by accident. It is rooted in institutional memory that predates the JMSDF itself. After Japan’s surrender in 1945, the remnants of the Imperial Navy’s first task was clearing mines from Japanese waters – both American and Japanese – to enable postwar reconstruction. When the Korean War broke out in 1950, the Japan Coast Guard’s Special Minesweeping Unit was dispatched at the request of the United States to clear mines around the Korean Peninsula, clearing 30 mines in an operation that cost one crew member’s life. This was years before the JMSDF formally existed.
The Cold War division of labour cemented the specialisation. The US Navy provided offensive firepower; the JMSDF acted as a gapfiller, making itself proficient at niche missions including minesweeping, anti-submarine warfare, and offensive submarine warfare. While other navies allowed their MCM capabilities to atrophy after the Cold War, the JMSDF continued investing – because Japan’s geography as a resource-importing island nation demands it.
The result in 1991 was decisive. After the Gulf War, the JMSDF dispatched four minesweepers, a fleet oiler, and a minesweeping tender to the Persian Gulf under Operation Gulf Dawn. They removed 34 mines without a single casualty. A US Navy officer assessed at the time that the Japanese would be “making a significant contribution” to what was expected to be the hardest phase of clearance operations.
The fleet today
The JMSDF currently operates 19 mine countermeasures vessels. The centrepiece is the Awaji-class, a modern MCM vessel with a fibre-reinforced plastic hull to reduce magnetic signature, LIDAR surveillance systems, Hitachi variable depth sonar, expendable mine disposal systems, and Remus 600 autonomous underwater vehicles for deep mine detection. Four are in service. The fifth was launched in December 2025. Nine are planned in total.
Beyond dedicated MCM vessels, the new Mogami-class frigates are designed with mine warfare capabilities using unmanned underwater vehicles and light minelaying equipment. As this class enters service, the total fleet with mine warfare capability could reach 46 to 50 vessels.
Compare this with the US Navy’s position in the Gulf: zero dedicated MCM ships, and a reliance on staff officers and EOD divers embedded with coalition forces.
The legal architecture already exists
The common assumption is that Article 9 of the Japanese constitution prohibits JMSDF deployment to the Hormuz. This is an oversimplification.
The 2015 security legislation, which Shinzo Abe pushed through parliament against fierce opposition, created three categories that could authorise overseas deployment. During the 2015 parliamentary debate, Abe repeatedly cited the specific scenario of a Hormuz Strait blockade as justification for the legislation. He argued that mine clearance during such a blockade could constitute an exercise of the right to collective self-defence under a “situation threatening Japan’s existence” (存立危機事態).
The Japan Times reported Takaichi’s nuanced position: Japan’s constitution would not bar mine clearance at the conclusion of the war. The barrier is not legal impossibility but political judgment about timing – whether the conflict is ongoing.
And here the alternative interpretation matters. Minesweeping in international shipping lanes can be framed not as an act of war against Iran, but as the protection of civilian vessels in international waters. Mines are indiscriminate weapons under the Hague Convention. Clearing them from a waterway that carries 20% of the world’s oil supply is arguably a humanitarian and navigational safety operation, not a military engagement with a sovereign state. The “important influence situation” (重要影響事態) category under the 2015 legislation could accommodate this framing – rear-area support operations short of combat, in waters adjacent to but not within an active combat zone.
Takaichi, a lifelong advocate of constitutional revision and strengthened defence, understands these distinctions better than most. Her public refusal is carefully worded: not “we cannot” but “we have not yet decided”.
What Takaichi cannot say
Here is the position Takaichi occupies on March 19.
She leads a minority government. The Japanese electorate overwhelmingly opposes involvement in the Iran war. The budget has just passed the lower house without a single opposition vote and faces a hostile upper house. Her political capital is finite.
She sits across from a president who started a war that has closed the strait through which 70-90% of Japan’s oil flows, who has publicly called on Japan by name to send warships, and who controls the trade and tariff levers that define Japan’s economic relationship with the United States.
She cannot say yes. The political cost domestically would be enormous. She cannot say no. The diplomatic cost with Washington would be severe, and she needs Trump on trade.
What she can do is what she has been doing: leave the door open. “Nothing has been decided.” “We are examining what can be done within our legal framework.” This is not indecision. It is positioning for the post-war scenario, when the shooting stops but the mines remain.
The 1991 playbook is the template. Japan did not participate in the Gulf War. But after the war, it dispatched minesweepers – and that deployment became the JMSDF’s defining overseas mission, the operation that proved Japanese forces could contribute meaningfully to international security without firing a shot.
If the Iran war ends in April or May and the strait remains mined, the political calculus changes overnight. Post-conflict mine clearance is reconstruction, not war. It falls squarely within the constitutional framework. It demonstrates Japan’s value to the alliance without crossing the Article 9 line. And it solves Japan’s own existential problem: getting the oil flowing again.
What to watch on Wednesday
The summit communique will not mention minesweepers. Look instead for:
The language on Japan’s “independent contribution” to regional security. If Takaichi commits to expanded defence spending, maritime security cooperation, or “all necessary measures to ensure energy security,” she is building the political foundation for a future deployment without committing to a timeline.
Any trade or tariff concessions from Trump. If Japan receives favourable treatment, the implicit expectation of a security contribution becomes harder to deflect later.
References to the 2015 security legislation or “situations with important influence.” If either side raises this framework, the minesweeper question has moved from hypothetical to operational planning.
And watch the BOJ decision the same day. If the Bank holds rates and acknowledges the oil shock as a constraint, it reinforces the existential nature of the Hormuz closure for Japan – which in turn strengthens the legal and political case for eventual deployment.
The country most vulnerable to the mine threat is the country best equipped to solve it. That irony is the subtext of everything Takaichi cannot say on Wednesday. The question is not whether Japan will send minesweepers. The question is when.
– 玉露
This article is not investment advice. All data as of 16 March 2026 unless otherwise noted.