Iran operates submarines in the Strait of Hormuz and the broader Gulf of Oman. The fleet is not large, and the vessels are not modern by the standards of major naval powers. What they represent is a persistent underwater presence in one of the world’s most difficult antisubmarine warfare environments — a shallow, thermally layered, acoustically cluttered body of water where detection is genuinely hard and where even a small submarine with limited capability poses a disproportionate threat to shipping and to surface naval forces.

China imports more oil than any other nation on earth. A majority of that oil originates in the Persian Gulf. The overwhelming majority of that Gulf oil moves through the Strait of Hormuz. This dependency is the most significant structural vulnerability in the Chinese economy, and Beijing has spent the better part of two decades trying to reduce it without succeeding in any meaningful way.

The arithmetic is unforgiving. China’s oil import dependence has risen, not fallen, as its economy has grown. Domestic production has plateaued and is declining at the margin. The non-Gulf sources that Beijing has cultivated — Russia, Angola, Brazil — are real but insufficient to replace Gulf supply. When analysts calculate what a thirty-day closure of Hormuz would do to Chinese industrial output, the numbers become politically significant very quickly. Beijing’s strategic planners know this. They treat it as the central energy security problem that has no clean solution.

A tanker that does not appear on tracking screens is not invisible. It is simply operating in the gap between the legal obligation to broadcast its position and the practical inability of enforcement authorities to impose consequences for failing to do so. Iran has exploited that gap systematically and at scale, building a sanctions evasion infrastructure that has kept its oil revenues flowing through periods when official exports were near zero, and learning, in the process, the operational techniques of maritime concealment that have military implications beyond their immediate commercial function.

The 2019 attack on the Abqaiq oil processing facility used cruise missiles and drones. The subsequent attacks on tankers in the Gulf of Oman used limpet mines and, in some cases, explosive-laden fast boats. By the time Houthi forces began their Red Sea campaign in late 2023, the weapons mix had evolved to include one-way attack drones and ballistic missiles fired against commercial vessels. The technological trajectory is consistent: unmanned systems are becoming a larger share of the threat to shipping in and around the Persian Gulf, and their characteristics — low cost, deniability, saturation potential, and steadily improving accuracy — make them a structural shift rather than a tactical adaptation.

Before February 2022, European energy security analysis treated the Persian Gulf as a significant but secondary concern. The primary vulnerabilities ran through Ukrainian pipeline corridors and Russian supply decisions. Hormuz was a risk to Asian energy markets, to oil prices globally, and to a residual flow of LNG from Qatar to a handful of European regasification terminals that had been built for flexibility rather than baseload supply. The invasion of Ukraine changed this with a speed that European energy planners had not fully modeled. By the end of 2022, Europe was competing in global LNG markets for volumes that included substantial Qatari supply, and its exposure to events in the Persian Gulf had become structurally different from anything its policy frameworks had anticipated.

The Strait of Hormuz has a sister chokepoint at the other end of the Arabian Peninsula. Bab-el-Mandeb, the narrow passage between Yemen and Djibouti that connects the Red Sea to the Gulf of Aden, carries the maritime traffic of the Suez Canal route — container ships, bulk carriers, tankers moving between Europe and Asia, and LNG vessels serving European regasification terminals. When Houthi forces in Yemen began attacking commercial shipping in the Red Sea in late 2023, they demonstrated that Iran’s sphere of proxy influence could threaten two of the world’s most critical maritime corridors simultaneously.

Fujairah sits on the Gulf of Oman coast of the United Arab Emirates, on the far side of the Hajar Mountains from Dubai and Abu Dhabi. For most of its history it was the smallest and least developed of the seven emirates, with a fishing economy and a geography that made connection to the Emirati interior difficult. What transformed Fujairah was the recognition, by Abu Dhabi planners and international oil traders simultaneously, that a port on the Gulf of Oman side of the UAE was worth more than a port on the Arabian Gulf side because it lay outside the Strait of Hormuz. Its strategic value is a function of what it avoids.

India sits at the northwestern edge of the Indian Ocean, closer to the Persian Gulf than any other major Asian economy except China. This geography is an asset — shorter transit times, lower shipping costs, access to Gulf labor markets that have sustained remittance flows for decades — and a vulnerability. The same proximity that makes Indian trade with the Gulf efficient makes Indian energy security exposure to Hormuz direct and consequential.

The strategic logic of Iran’s Hormuz threat rests on the assumption that the cost of closure to the outside world exceeds the cost of closure to Iran. This assumption is correct in relative terms and misleading in absolute terms. Iran would suffer severely from a Hormuz closure that it initiated. Its oil exports, its import supply chain, and its remaining international financial connections all depend on the strait remaining open. The question is whether the political leadership in Tehran would initiate a closure despite these costs, and under what conditions the answer would be yes. The Iranian domestic economy is the ledger that answers that question.

Iraq is the second-largest producer in OPEC and the country most completely helpless in a Hormuz closure scenario. Nearly all of its oil exports — the revenue that funds approximately 90 percent of the government’s budget — move through terminals near Basra in the far south of the country, load onto tankers in the northern Gulf, and transit the strait to reach their buyers. Iraq has no bypass pipeline capacity of consequence, no alternative export route, and no political influence over the parties whose conflict would cause the closure. It is a bystander to its own financial ruin.