Hormuz crisis raises fears of Asia straits weaponisation

The crisis in the Strait of Hormuz, which began after Iran’s Revolutionary Guard closed the waterway in late February and targeted ships with drones, anti-ship missiles and mines, has raised warnings that waterways in Asia could be weaponised.

According to Foreign Affairs, the episode showed that low-cost tools such as coastal surveillance systems, drones, mines and unmanned boats can give weaker states the ability to disrupt shipping and impose high costs on stronger rivals, even without fully closing a strait.

During the war, the Iranian Revolutionary Guard set up a transit fee system in the Strait of Hormuz that required ships to provide documents and pay charges to pass through. Unconfirmed reports said one ship paid $2 million to cross the strait, while many shipping companies refused to pay, citing international law rules.

Legal concerns over blockade orders

In April, U.S. President Donald Trump said the U.S. Navy would impose a naval blockade on the Strait of Hormuz, which raised legal concerns linked to the United Nations Convention on the Law of the Sea and the laws of maritime conflict. U.S. Central Command later revised its guidance so that it applied only to ships heading to or leaving Iranian ports.

The developments tied to Hormuz suggest that the mere threat of closing straits is enough to raise marine insurance costs, reroute shipping lanes and disrupt energy and commodity markets. The same picture has deepened fears in Asia, where the main straits carry global trade, energy and semiconductors, not only oil as in Hormuz.

Malacca, Taiwan and Luzon

The Strait of Malacca is one of the waterways most exposed to any attempt to disrupt navigation or impose restrictions. At its narrowest point it is 1.5 nautical miles wide, and about 40% of global trade and 80% of China’s energy imports pass through it.

There are also growing concerns that what happened in Hormuz could encourage similar methods in the Strait of Malacca, the Taiwan Strait or the Luzon Strait, whether through blockade, fee collection or disruption of sea traffic during crises. For years, China has sought to reduce its dependence on Malacca by expanding overland pipelines, Indian Ocean-linked ports and polar routes, in what is known as the “Malacca dilemma.”

Semiconductors and military strategy

The Taiwan Strait carries about 20% of global maritime trade and brings extra risks because of its direct link to the semiconductor industry. Taiwan dominates global production of advanced chips, while the main ports are concentrated on the west coast facing the strait.

Estimates cited in the report say any blockade of the Taiwan Strait could result in a loss equal to 5.3% of global gross domestic product. Hormuz has also reinforced military thinking in Asia by renewing the view that maritime straits can be turned into effective tools of pressure and blockade even against major powers.

The latest developments have given added momentum to China’s “anti-access/area denial” strategy, known as A2/AD, which seeks to restrict adversaries’ movement in waters around China through a multi-layered network of missiles, naval and air capabilities and surveillance systems. Taiwan, in response, continues to develop what is known as the “porcupine” strategy, based on mobile and dispersed defence systems designed to make any invasion attempt costly and complex.

In the Luzon Strait, which links the South China Sea and the Pacific Ocean, the United States and the Philippines have intensified exercises aimed at developing capabilities to disrupt navigation, while China has responded with live-fire drills near the area. As concerns rise over disruption to key straits, attention is also turning to Indonesia’s secondary passages, including the Sunda Strait and the Lombok Strait, especially after Jakarta discovered an unmanned underwater vehicle suspected of being Chinese in the Lombok Strait in April.

Observers have called for stronger protection of sea lanes, the development of alternative ports and a reduction in global dependence on semiconductor production in Taiwan, saying the Hormuz crisis showed how turning straits into tools of pressure and conflict can threaten the entire global economy.