If the Strait of Hormuz Closes — What Japan Faces After a US-Israel Strike on Iran

Approximately 90% of Japan’s crude oil imports pass through the Strait of Hormuz. When analysts model the consequences of a US-Israel military operation against Iran severe enough to prompt Iranian retaliation against Gulf shipping, Japan appears consistently as among the most economically exposed non-combatant nations.

The Scenario

Iran has several credible mechanisms for disrupting Hormuz traffic: mines, anti-ship missiles, and the threat of action by proxy forces against Gulf state infrastructure. A significant disruption — even one lasting weeks — would create immediate supply pressure on Japanese refiners and generate price effects across the economy.

Japan’s Strategic Constraints

Japan maintains strategic petroleum reserves, officially sufficient for approximately 90 days of consumption. But reserve drawdown is a time-buying measure, not a solution. Japan has no domestic oil production and limited ability to redirect supply chains on short timelines. The country’s energy transition investments in renewables and hydrogen are real but not yet sufficient to materially reduce this vulnerability.

What This Means Practically

For Japanese businesses, the Hormuz scenario is not abstract. It affects logistics planning, energy cost projections, and the political calculus of Japan’s relationship with the United States. Japan’s formal security alliance with the US creates implicit pressure to support operations that could directly damage Japanese economic interests. This tension is not new, but the current Middle East situation makes it more acute.

Analysis based on public reporting. Global Watch Japan.