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.

The Strait of Hormuz is 90 miles long and between 21 and 55 miles wide. The navigable channel — the portion deep enough for laden very large crude carriers and the other substantial vessels that transit it — is much narrower. Two traffic separation lanes, each approximately two miles wide, handle the inbound and outbound commercial traffic, separated by a two-mile buffer zone. The effective transit corridor for a laden supertanker is therefore something on the order of two miles across, within a strait that appears much wider on maps but that shallow water, islands, and navigational hazards reduce to a constrained passage at the critical point.