A vessel transits near the Strait of Hormuz on March 11. (©Reuters/Kyodo)
Japan has the right of self-defense if a disruption in the Strait of Hormuz severely damages its economy, according to Nobukatsu Kanehara, a senior national security official under the Shinzo Abe administration.
"If an international strait were effectively shut down and the economy crippled, Japan would be justified in exercising its right of collective self-defense," Kanehara, who served as Assistant Chief Cabinet Secretary from 2012 to 2019, said in an interview.
Such a determination would permit Japan to use limited force to escort tankers, conduct mine-clearing operations, and back US forces where necessary.
The Hormuz Test
Following the US-Israel strikes on Iran in February, Tehran has intermittently threatened and constrained traffic through the Strait of Hormuz, a chokepoint through which roughly one-fifth of global oil and more than 90% of Japan's crude imports transit.
Experts warn that any sustained disruption would carry short- and long-term consequences for global energy security and economic stability. "What Iran is doing amounts, in substance, to an economic blockade," Kanehara, now a senior advisor at The Asia Group, said.
Under Japan's current legal framework, the use of force is tightly constrained by Article 9 of the Constitution, which renounces war and limits the maintenance of armed forces.
Yet a 2014 reinterpretation under Abe and subsequent security legislation opened the door to the exercise of limited collective self-defense in situations deemed to threaten national survival.
Kanehara, a key architect of the legislation, suggested that a prolonged conflict could meet that threshold. "Depending on the circumstances, even the use of individual self-defense could be justified," he added.
Betting on Trump's Diplomacy
For now, however, he stopped short of calling the situation acute. Japan holds more than six months' worth of oil reserves, offering a buffer against short-term shocks. And at this early stage of the war, expectations of a negotiated end still linger.
"Many still expect the conflict to end relatively soon, and that President Trump would come to some form of negotiated settlement," he said.
In his view, Washington's military posture reflects that expectation. While the United States has begun deploying more assets toward the Middle East, Kanehara downplayed the scale of current deployments.
Reports of troop mobilizations in the thousands, he noted, fall well short of what would be required for a decisive ground campaign.
"Iran is a country of 90 million people with vast territory," he said. "To truly subdue it would require something on the order of 100,000 troops."
Instead, the former official expects the US to use its posture as bargaining leverage to push Tehran toward a ceasefire rather than a major escalation, and said Tokyo should carefully assess the situation and prepare to send in support once such a settlement materializes.
"Even if a ceasefire is reached, naval mines would prevent safe passage through the strait," Kanehara said. "If mines are indeed laid, it would be both logical and necessary for Japan to engage in mine-clearing operations and the protection of tanker traffic."
Japan's Postwar Shackles
Kanehara also noted that the latest conflict in the Middle East has once again exposed structural constraints in Japan's defense posture, one rooted in its postwar constitutional framework.
"Under the Abe administration, Japan pushed the interpretation of Article 9 to its limits," he said, adding that the priority now should be to remove Paragraph 2 of that Article.
Paragraph 2 states that Japan will not maintain "land, sea, and air forces," a clause long reinterpreted to allow the existence of the Self-Defense Forces, but one that continues to create legal ambiguity.
For Kanehara, it remains a vestige of postwar settlement.
"As a defeated nation, Japan was bound by what amounts to a punitive constraint denying it the right to maintain armed forces," he said. "It is time to move beyond those nonsensical postwar shackles."
Resources Under Pressure
Beyond the immediate crisis, the ex-official pointed to a longer-term concern of strategic overstretch. Prolonged US engagement in the Middle East, Kanehara argued, risks diverting resources away from other regions at a time when global commitments are already stretched thin.
"If US resources are continuously depleted in one theater, its ability to focus elsewhere diminishes," he said. "In Northeast Asia, that would translate into a weakened capacity to contain China."
Already, the US has burned through large quantities of precision munitions in weeks, with reports suggesting it has drawn down years' worth of some stockpiles, including Tomahawk cruise missiles.
Some of its air defense systems in South Korea, along with naval forces from Okinawa, have also been repositioned to the Middle East, underscoring the growing strain on America's regional posture.
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Author: Kenji Yoshida
