Should Japan Send Warships to the Strait of Hormuz?

Following US President Trump’s expression of expectation that Japan would send ships to the Strait of Hormuz in the Middle East, the Japanese government will be forced to make a difficult decision. Japan prioritizes the Japan-US alliance in security matters, but on the other hand, it imports large quantities of energy from the Middle East, placing it in a dilemma.

Many within the Japanese government believe that it is currently difficult to send Self-Defense Force ships to the conflict-ridden Middle East, and that they will carefully observe the true intentions of the US.

A senior Japanese government official, in an interview with the Nikkei Asian Review on the evening of March 16, stated that “the government is taking a cautious approach to dispatching the Self-Defense Forces.” The official added, “We will convey to the US what Japan can and cannot do,” expressing a negative attitude towards dispatching the Self-Defense Forces.

The Japan-US summit will be held in Washington on March 19. Considering that Trump may directly request Japan to send ships, the Japanese government has already begun private consultations with the US. Japanese Prime Minister Sanae Takaichi stated at a meeting of the House of Councillors Budget Committee on March 16 that a comprehensive discussion is underway regarding the dispatch of ships to the Strait of Hormuz. Takaichi stated, “We are studying what can be done within the legal framework to protect the lives of relevant Japanese ships and crew.”

She emphasized that she had not received a formal request from the United States to escort the ships. She stated that no decision had been made to dispatch the Self-Defense Forces, adding that ordering maritime security operations based on the Self-Defense Forces Law would be “legally very difficult.”

On the same day, Japanese Foreign Minister Toshimitsu Motegi held a telephone consultation with US Secretary of State Marco Rubio. He stated that to ensure navigational safety in the Strait of Hormuz, Japan would cooperate with the international community, including the United States, and take all necessary diplomatic efforts. A source from the Japanese Ministry of Foreign Affairs stated that during this telephone consultation, the US did not request Japan to dispatch ships to the Strait of Hormuz.

Japan has consistently avoided directly commenting on the US and Israel’s attacks on Iran. This is because US military actions are difficult to legally assess, and Japan’s traditional friendly relations with oil-producing Iran must also be considered. On March 14, Trump stated on his social media that he expected relevant countries, including Japan, to send ships to the Strait of Hormuz, increasing Japan’s sense of urgency. If Trump directly makes this request to Takaichi during the summit meeting on the 19th, it could put pressure on the US-Japan alliance to “choose sides.”

A similar incident occurred in 2019. As tensions between the US and Iran deepened, an oil tanker was attacked in the Strait of Hormuz. The US planned to form a coalition to protect civilian vessels in the Strait of Hormuz and sought assistance from Japan.

Ultimately, then-Japanese Prime Minister Shinzo Abe did not join the coalition and chose to protect Japanese civilian vessels alone. In 2020, based on the Defense Ministry Establishment Law, Japan dispatched Maritime Self-Defense Force destroyers to coastal waters outside the Strait of Hormuz under the guise of “research and investigation,” to gather intelligence and escort Japanese ships. This decision took about six months to make.

In the 2019 discussions within the Japanese government, four main legal options were considered for allowing the Self-Defense Forces (SDF) to join a coalition of willing participants: (1) utilizing the Security-Related Laws, which stipulate the right of collective self-defense and provide logistical support to other countries’ militaries; (2) maritime security operations based on the Self-Defense Forces Law; (3) applying the Anti-Piracy Law; and (4) enacting a special measures law. The framework for this discussion is expected to be similar. All four possible legal options present challenges.

If based on the Security-Related Laws, the prerequisite is that the supported entity attempts a counterattack in accordance with international law. The Japanese government is unwilling to evaluate the US attack on Iran from an international legal perspective.

The Security-Related Laws stipulate that the SDF can participate in “international peace and joint response to situations” when the international community takes joint action to eliminate threats. Joining a coalition of willing participants is similar to this, but requires a UN resolution.

If maritime security operations are conducted under the Self-Defense Forces Law, only ships registered in Japan can be protected.

Then, can the Anti-Piracy Law be applied? When Japan enacted this law in 2009, it was based on the premise of participating in joint responses with other countries. Regardless of ship nationality, it could escort vessels from other nations. However, the law’s targets were limited to so-called “piracy.” It did not envision protecting ships from Iranian attacks in the Strait of Hormuz.

To fully address these legal arguments, Japan needs to establish a legal system adapted to the current situation. Legislative work, including drafting bills and parliamentary deliberations, will take considerable time. Compared to 2019, a full-scale armed conflict has now effectively begun, the Strait of Hormuz is practically blocked, and the urgency of the situation is much greater.

The situation with Iran is far more chaotic than it was then, and Japan’s space for diplomatic maneuvering is shrinking. China and North Korea are increasing their military buildup, and Trump is also imposing tariff pressure on allies. Japan will be forced to respond to a more complex international situation than it was then.

Nikkei