The weaponization of shipping channels

Could imposing a toll to pass through the Strait of Malacca, the narrow stretch of water that connects the Indian Ocean with the Pacific, be a profitable business? Indonesia's Finance Minister Purbaya Yudhi Sadewa seemed to float the idea at the end of April. "If we split it three ways between Indonesia, Malaysia, and Singapore, that could be quite something, right?" he said.

He later clarified that he was not being entirely serious, after Indonesian Foreign Minister Sugiono said that his country supported the freedom of navigation and would not be imposing tolls on vessels passing through the strait, which runs between Indonesia, Malaysia, and Singapore.

Nonetheless, the remark raised the specter of maritime traffic being misused for geopolitical leverage, not just in the Strait of Hormuz, but in other waterways, too. "The closure of the Strait of Hormuz has forced policymakers in Asia to face questions over the security of other maritime chokepoints," wrote the Reuters news agency.

The Strait of Malacca is of particular concern. This is the most important shipping route between East Asia, the Middle East, and Europe, accounting for around 22% of international maritime trade.

How small waterways make big powers vulnerable

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Dangers of geopolitical leverage

But there are other issues of concern besides piracy and regional conflict. In November last year, the Center for Strategic and International Studies (CSIS) warned of this new danger.

Even non-state actors are now in a position to serious disrupt the flow of global trade, the think tank said, citing attacks by the Houthi militia in the Red Sea. Many shipping companies now avoid passing through the Suez Canal, taking the longer route around the Cape of Good Hope instead, which significantly impacts supply chains and prices.

Political scientist Nikolaus Scholik, former colonel in the Austrian army and senior advisor at the Austria Institute for European and Security Policy (AIES), believes that these are signs of a fundamental change in the geopolitical balance of power.

"We are experiencing today the consequences of a development in which individual states believe they can legally dominate strategically important maritime straits," he told DW. It would be particularly dangerous, he added, if straits like Hormuz, Malacca, or Taiwan were to become levers of geopolitical influence.

Christian Wirth, Asia analyst at the German Institute for International and Security Affairs (SWP), agrees. "Whether a strait is particularly vulnerable depends essentially on three factors: The transport agreement, potential alternative routes, and the political situation in the surrounding area," he told DW. The more important a route is, and the harder it is to bypass, the greater its strategic significance.

'Return of geography'

The Strait of Hormuz, through which a large quantity of global oil and gas exports must pass, is looking particularly vulnerable right now. But Scholik warns that we shouldn't only be looking at the Persian Gulf. "In such a situation, the Taiwan Strait would be even more significant than the Strait of Hormuz," he says, referring to a possible conflict between China and Taiwan. As he points out, a large proportion of Asian trade passes through the Taiwan Strait, as well as through the Strait of Malacca.

The International Institute for Strategic Studies (IISS) recently wrote that geopolitics is currently experiencing the "return of geography." Straits like Hormuz, Bab el-Mandeb or Taiwan are no longer mere geographical passages; they are increasingly becoming strategic levers of geopolitical power. The IISS argues that the close interconnectedness of the world has created new dependencies, and thus also new means of exerting pressure.

In international law, the situation is very clear. "The principle of free transit applies to maritime straits of international importance," said Wirth. "This means that ships, even warships, are allowed to pass unhindered ... through straits that are classified as international waters."

A blockade of an international strait would thus be a serious violation of international law, Wirth said. The United Nations Convention on the Law of the Sea guarantees even warships peaceful passage through coastal waters that are defined as territories of the states bordering the strait. Tolls or charges are categorically inadmissible. They may only be levied on artificial waterways such as the Suez or Panama Canal.

The fragility of maritime law

But the real problem is the political realities, said Scholik: "International law only functions if the countries involved are prepared to observe it." That is of course not always the case: In a recent case in the South China Sea, China ignored a ruling by the international Court of Arbitration in the Philippines' favor.

At the same time, experts warn against overestimating conventional military power. "These days, you no longer need a big navy to severely disrupt [traffic through] a strait," said Scholik. Iran, he comments, has shown how small speedboats, missiles, or drones can exert considerable pressure. 

However, Wirth argues that the total blockade of a strait also carries huge risks for the state doing the blocking, which generally also suffers economic damage. In the event of an escalation in the Taiwan Strait or the Strait of Malacca, China too would be massively affected.

There are some alternative routes in southeast Asia, such as the Sunda Strait between Sumatra and Java, or the Lombok Strait between Lombok and Bali. Transport through these alternatives is longer and more expensive, but global trade would not be completely suspended if the straits of Taiwan or Malacca were blocked, Wirth said.

Maritime chokepoints

Nonetheless, both experts agree that the globalized economy is becoming increasingly vulnerable. Scholik refers to the "just in time" principle of modern supply chains. Companies hardly keep any goods in stock, which means that even brief interruptions are capable of causing worldwide economic damage.

For that reason, the Center for Strategic and International Studies has warned that the Strait of Hormuz is a symptom, not an exception: The modern global economy relies on a handful of maritime chokepoints, with the potential for global consequences if any are disrupted.

This is why the repercussions of the Malacca debate extend well beyond southeast Asia. The forceful reaction by Singapore, Malaysia, and Indonesia to the suggestion of transit charges demonstrated how tempting it has become to use geographical control as political or economic leverage, but also that calling into question the freedom of navigation represents a serious threat to the world economy.

This article has been translated from German.