The Coming Contest for Asia’s Waterways

Iran’s Islamic Revolutionary Guard Corps (IRGC) escalated tensions in late February by threatening to close the Strait of Hormuz, warning that any ship attempting passage would be targeted with drones, antiship missiles, and mines. The move disrupted Middle Eastern oil exports and sent global energy prices surging, demonstrating how modern technology—such as coastal surveillance, drones, and mines—allows weaker states to impose significant economic costs on stronger adversaries. The Strait of Hormuz has historically been a flashpoint, with Iran previously laying mines during the 1984 tanker war and the UK blocking oil exports in 1951 after Iran nationalized its oil industry. However, this latest crisis differs in scale and intent, as the threat of disruption alone has already raised shipping insurance premiums, rerouted global trade, and destabilized commodity markets. The U.S. and Israel responded with strikes on Iran, while former U.S. President Donald Trump threatened a naval blockade of the strait, further violating international law governing transit passage under the UN Convention on the Law of the Sea (UNCLOS). Asia faces even higher stakes, as its waterways control critical trade, energy, and semiconductor supply chains. The Hormuz crisis could embolden similar tactics in the Indo-Pacific, such as U.S. restrictions on the Strait of Malacca, a Chinese blockade of the Taiwan Strait, or joint U.S.-Philippine controls over the Luzon Strait. Secondary maritime corridors, like those in Indonesia’s archipelago, are also becoming focal points for geopolitical maneuvering as both Washington and Beijing anticipate disruptions. After U.S. and Israeli strikes in late February, Iran introduced a structured toll system in the Strait of Hormuz, requiring vessels to submit documentation and pay fees for passage. While reports suggested at least one ship paid $2 million, most shipping companies refused, citing violations of international navigation laws. By mid-April, negotiations to reopen the strait collapsed, and Trump declared the U.S. Navy would blockade all ships attempting to enter or leave, raising legal concerns under UNCLOS and the law of armed conflict at sea. The 21-nautical-mile-wide Strait of Hormuz falls under UNCLOS transit passage rules, which guarantee unimpeded navigation for ships and aircraft. Though the U.S. has not ratified UNCLOS, it generally respects these principles. The current standoff underscores a broader shift: weaker states now have the means to disrupt global trade, while major powers increasingly disregard international norms to enforce their interests, risking prolonged economic and legal fallout.