The Day the Strait Closes — Japan's Structural Vulnerability in Energy Security

On February 28, 2026, US and Israeli forces launched strikes against Iran, killing Supreme Leader Khamenei. Iran immediately declared the effective blockade of the Strait of Hormuz — the world's most critical oil shipping route connecting the Persian Gulf to the Gulf of Oman. As of March 17, 2026, more than two weeks into the blockade, the closure continues, with over 150 oil tankers[1] stranded inside the Persian Gulf.

The Strait of Hormuz is approximately 33 km wide at its narrowest point, with navigable shipping lanes of only about 6 km. Yet through this bottleneck flows an average of 20 million barrels per day[2], which the EIA equates to about 20%[2] of global petroleum liquids consumption. Approximately 3,400 tankers[3] bound for Japan pass through annually, with roughly 80% of Japan's crude oil tankers dependent on this strait.

Prime Minister Sanae Takaichi announced on March 11 the release of approximately 80 million barrels (45 days' worth)[4] from strategic petroleum reserves — the largest release in Japan's history. The decision was made unilaterally, before the coordinated release agreed upon by IEA's 32 member nations. But a reserve release is merely buying time — so long as the blockade continues, physical replenishment is impossible.

The Structure of Japan's Energy Dependence

Japan's Energy Imports and Strait of Hormuz Dependence

Crude Oil ImportsMiddle East: 93.5%

Via Hormuz: ~90%

LNG ImportsMiddle East: ~10.8%

Via Hormuz: ~6.3%

Via Strait of HormuzNot via Hormuz

Major LNG suppliers (Australia 39.7%, Malaysia 14.8%, Russia 8.9%) do not transit the Strait of Hormuz

Japan's dependence on the Middle East for crude oil imports stood at 94.7%[5] in FY2023, after a record 95.2%[6] in FY2022, with virtually all of it transiting the Strait of Hormuz. The main suppliers are Saudi Arabia, the UAE, Kuwait, Iraq, and Qatar — a geographic concentration that stands out globally.

The asymmetry between crude and LNG

For LNG, the situation is different. According to JETRO's March 2026 analysis, Japan's LNG import dependence on the Strait of Hormuz is only approximately 6.3%[7]. The largest import sources are Australia (39.7%), Malaysia (14.8%), and Russia (8.9%), none of which transit the Strait of Hormuz.

This reveals an asymmetric structure: electricity is relatively insulated, crude oil is the critical vulnerability. Since petroleum products account for approximately 35% of Japan's primary energy supply, a disruption to crude oil routes directly affects gasoline, kerosene, plastics, and transportation costs. The impact on households and industry will materialize far faster and far more severely than electricity prices.

The Reserve System and Its Limits

Japan's petroleum reserves at the end of April 2025 stood at 211 days on an IEA basis[8] — 123 days[8] of national reserves, 80 days[8] of private-sector reserves and 8 days[8] of joint reserves with oil-producing countries — a level that ranks among the more robust internationally (251 days in total under the Petroleum Stockpiling Act basis).

However, this crisis differs fundamentally from the 1990 Gulf Crisis. When Iraq invaded Kuwait in 1990, the Strait of Hormuz itself was not blocked; oil could still physically be shipped out. Japan managed through reserve drawdowns and alternative procurement from non-Middle Eastern producers. The 2026 crisis presents a structurally different scenario: "Oil exists, producers want to export it, but it physically cannot be moved." Replenishment of released reserves is impossible while the blockade continues — inventory only declines over time.

The 45-day release was the right call, but it has merely "bought 45 days." If the blockade exceeds three months, a substantial depletion of reserves and a prolonged price surge become unavoidable.

The Reality of Alternative Routes

The most practically viable alternative is the UAE's ADCOP (Habshan-Fujairah) pipeline, which runs approximately 360 km from Abu Dhabi's inland Habshan terminal to the Fujairah port on the Gulf of Oman, bypassing the Strait of Hormuz. Following the crisis, utilization surged to 2.4 million barrels per day[9] during March 4–9.

Yet the pipeline's designed maximum capacity is 1.5–1.8 million barrels per day[10] — under a tenth of normal Hormuz throughput (20 million barrels a day). Saying "there is an alternative route" dramatically misrepresents reality: alternatives cover well under a tenth, leaving the rest unresolved.

The Cape of Good Hope (southern Africa) detour route faces the same fundamental limitation. It can only apply to cargo that has already exited the Strait of Hormuz — adding 30+ additional shipping days — and provides no solution for the 150+ tankers currently trapped inside the Persian Gulf. Furthermore, since the Red Sea (Suez Canal route) is also impaired by Houthi attacks, effective alternative routes have essentially vanished, creating a "double blockade" scenario.

Economic Impact Scenarios for Households and the Macro Economy

Gasoline Prices Hit Households Harder as the Blockade Continues

Current (with subsidy)¥161–165/L

Suppressed by government subsidies

Without subsidy¥185–200/L

Estimated if subsidies end

Blockade for monthsOver ¥200/L

Crude at $100–120/barrel

Blockade for 1 yearOver ¥328/L

¥36,000/yr household burden · GDP -0.6%

⚠ Reserves deplete the longer the blockade continues, and replenishment is impossible while the strait remains closed

Current gasoline prices are being held to approximately ¥161–165 per liter[1] with government subsidies, though estimates suggest prices would reach ¥185–200/L without subsidies. Nomura Research Institute runs three scenarios. Its base case, with crude holding at $87 a barrel, cuts real GDP by 0.18%[11] over a year. Its pessimistic case — a full closure of the strait with crude at $140 — cuts it by 0.65%[11], puts the national average gasoline price at ¥204[11] per litre, and raises electricity bills by ¥792[11] a month, or ¥9,508[11] a year.

The Structural Problem of 94.7% Dependence

The argument to "reduce Middle East dependence" has continued for decades. Yet the figure stayed at 94.7% in FY2023 — not simply because of "policy failure." Middle Eastern crude is highly cost-competitive, distances are manageable, and quality is reliable. Alternative sources such as American or Canadian crude bring substantially higher transportation costs; Russian crude raises sanctions concerns.

The problem is that the aggregate of individually rational procurement decisions creates a massive systemic risk at the national level: "dependence on a single chokepoint — the Strait of Hormuz." When left to market mechanisms, optimization occurs at the company level, but national-level risk diversification does not happen automatically.

The Energy Security Case for the Green Transition

The Japanese government's GX (Green Transformation) plan calls for public-private investment of over ¥150 trillion[12] (of which ¥20 trillion[12] is state-led advance support) over ten years, targeting 10 GW of offshore wind by 2030 and 30–45 GW by 2040. This policy has been framed primarily as an environmental response, but the current crisis offers a different lens.

Nobuyuki Fukushima argues in 『エネルギー政策は国家なり』 (Energy Policy Is Nationhood)（外部サイト、新しいタブで開きます） (『エネルギー政策は国家なり』) that energy security must be reconceived not as an environmental issue but as a foundation of national survival. The transition to renewable energy can be reframed as "the cost of avoiding Hormuz risk." As the power sector decarbonizes, the proportion of electricity costs directly tied to crude oil prices and shipping lane disruptions will decline. While the investment needed for renewables and energy security enhancement through 2035 is estimated at ¥38 trillion, compared to the GDP losses from a year-long blockade, this represents a rational insurance investment.

Not environment versus economy

The false dichotomy of "environment versus economy" is challenged by this crisis. The transition to renewables is not an environmental concession — it is a national security strategy to avoid entrusting the fate of the nation to the Strait of Hormuz.

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For more on the integration of energy policy and GX investment, see also "Integrating Climate Change and Social Policy（このサイトの記事）."

References

Amid regional conflict, the Strait of Hormuz remains critical oil chokepoint — EIA (U.S. Energy Information Administration) (2024)

Japan's LNG import dependence on the Strait of Hormuz is 6.3% — JETRO (Japan External Trade Organization) (2026)

Impact of Rising Oil Prices Due to Iran Situation on Japan's Economy and Household Finances — Nomura Research Institute (Takahide Kiuchi) (2026)

Government to Release Strategic Petroleum Reserves as Early as March 16 — Prime Minister Takaichi Announces Record 45-Day Release — Nikkei Shimbun (2026)

Petroleum Reserve Status — June 2025 — Agency for Natural Resources and Energy (METI) (2025)

Hormuz Strait Passage Halted Amid Deteriorating Middle East Situation — JETRO (Japan External Trade Organization) (2026)

Japan faces accelerating inflation risk as oil prices surge amid effective Hormuz blockade — Bloomberg Japan (2026)

Reference Books