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.

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.

Kuwait remembers. Of all the Gulf states whose oil revenues depend on Hormuz transit, Kuwait is the one with the most direct experience of what it looks like when a regional power decides that its neighbors’ sovereignty and economic interests are subordinate to its own strategic ambitions. The Iraqi invasion of August 1990 and the seven-month occupation that followed were not a Hormuz closure, but they were something equivalent in economic and political terms: the abrupt elimination of Kuwait’s ability to govern itself and export its oil. The institutional memory of that period shapes Kuwaiti foreign policy in ways that are distinct from the other Gulf states that have not experienced occupation.

The United States Naval Forces Central Command, headquartered at Naval Support Activity Bahrain, is responsible for an area of operations that covers approximately 2.5 million square miles of water. Within that vast theater, no piece of geography concentrates more of its attention, resources, and contingency planning than a transit corridor that is, at its most critical point, narrower than the distance between Manhattan and New Jersey.

The Fifth Fleet’s dilemma is structural. Its mandate is to ensure freedom of navigation through Hormuz and the broader Gulf. The force it faces — the IRGCN — has designed itself specifically to make that mandate as expensive as possible to execute. The disparity in capabilities runs entirely in one direction, and the disparity in objectives runs in the other. The US Navy can destroy every Iranian naval vessel in the Gulf in days. It cannot do that without triggering an escalation sequence that closes the strait for weeks. The IRGCN cannot defeat the Fifth Fleet. It can make the Fifth Fleet’s success cost more than Washington wants to pay.

The Islamic Revolutionary Guard Corps Navy does not train to defeat the United States Navy in open water. It trains to make the cost of operating in the strait prohibitive. These are different strategic problems with different solutions, and the IRGCN has spent four decades refining the second one while ignoring the first.

The doctrine that has emerged from this period is sometimes called asymmetric maritime warfare, which is accurate as far as it goes. What the label understates is the geographic specificity of the strategy. The IRGCN is not a general-purpose force. It is a Hormuz force. Every element of its order of battle — the fast attack craft, the anti-ship missile batteries, the submarine fleet, the mine warfare capability, the shore-based artillery — is oriented around the same twenty-one-mile problem.