In late February, Iran’s Islamic Revolutionary Guard Corps (IRGC) moved to close the Strait of Hormuz, issuing warnings that “if anyone tries to pass, the heroes of the Revolutionary Guard and the regular navy will set those ships ablaze.” By targeting ships with drones and antiship missiles and laying mines, Tehran has choked off oil exports from the Middle East and sent energy prices soaring. The control of waterways has long been used to thwart adversaries and shape strategic outcomes. In 1951, after Tehran nationalized its oil industry, the United Kingdom used naval pressure to prevent Iran from exporting oil. During the 1984 “tanker war,” Iran laid mines in the Strait of Hormuz and harassed ships in response to Iraqi attacks. Throughout both these conflicts, however, the Strait of Hormuz remained in use. What the current Hormuz crisis makes plain is that closing a strait has become easier and the consequences more far-reaching.…