Japan Faces Two Major Risks if the Strait of Hormuz Is Closed

The US and Israeli attacks on Iran have cast a huge shadow over Japan’s energy security. The biggest risk is the ability to navigate the vital maritime route of the Strait of Hormuz. Iran has reportedly announced a ban on all ships. A de facto blockade, if prolonged, would have enormous consequences.

The Strait of Hormuz lies between Iran and the Arabian Peninsula, and at its narrowest point, it is only 33 kilometers wide. Because a quarter of global oil trade passes through it, there have been numerous past concerns about a potential blockade or similar situations.

During the Iran-Iraq War in the 1980s, both sides attacked oil tankers with missiles to prevent each other’s oil exports. Iran has mentioned the possibility of a blockade when the US and Europe imposed economic sanctions on Iran’s nuclear program in 2011 and when the first Trump administration withdrew from nuclear negotiations in 2018. Iran also hinted at a blockade when the US and Israel attack it in June 2025.

However, Iran has never implemented one so far. This would not only prevent Iran from exporting its own oil, but also potentially impact China, the largest oil importer. However, the assassination of Supreme Leader Khamenei raises concerns that Iran may be determined to use its “ban” measures and escalate to a full-scale blockade.

Japan relies on the Middle East for 96% of its crude oil imports, most of which pass through the Strait of Hormuz. If the embargo is extended, two major concerns arise regarding energy security. One is supply disruption, but having learned from the lessons of the two oil crises of the 1970s, Japan currently has reserves sufficient for approximately 250 days of domestic consumption. The risk will not be immediately apparent, and there is time to find alternative purchases.

The other risk is rising crude oil prices, a challenge faced globally, but particularly burdensome for Japan, whose procurement costs are already rising due to the yen’s depreciation. Japan’s dependence on the Middle East for liquefied natural gas (LNG), used for power generation and city gas, is currently around 10%, but since LNG import prices are linked to crude oil prices, related costs will also inevitably rise.