Narrow waterways that command critical sea-lanes. Ships carry about 85% of the world's exports by volume (or 55% by value), according to Clarksons, a shipping broker, making the security of these passages a matter of global economic importance. "A lot of people are going to wake up to the fact that maritime trade is of great value and has to be protected," says Steven Wills of the Centre for Maritime Strategy, an American think-tank.
Sir Jacky Fisher, a Victorian admiral, identified five "strategic keys" that "lock up the world": Singapore, Cape Town, Alexandria, Gibraltar and Dover. The importance of such chokepoints has been apparent since antiquity: during the Peloponnesian war in the 5th century BC, Sparta's capture of the Dardanelles, impeding the flow of grain from the Black Sea, forced hungry Athens to surrender.
The Strait of Malacca is the world's busiest and oiliest chokepoint by most measures. The Strait of Hormuz provides a fifth of the world's oil and liquefied natural gas but is the only sea passage out of the Gulf, making its closure especially disruptive. The Danish and Turkish straits are likewise the sole route to the seas beyond.
The Bab al-Mandab strait, between Yemen and the Horn of Africa, used to carry 9% of world trade but carried only 4% as of early 2026, after Houthi drone and missile attacks from 2023 to 2025 diverted shipping around Africa. The Suez Canal was blocked for years during Arab-Israeli enmity. The Panama Canal handles about 40% of American container traffic but accounts for just 3% of maritime trade; droughts linked to climate change have led to repeated restrictions on the number of ships able to use it. Nicaragua dreams of building a rival canal.
Other chokepoints include the Strait of Gibraltar, the English Channel, and the Kattegat, Skagerrak and Oresund off Denmark connecting the Baltic and North seas. The Turkish Bosporus and Dardanelles are regulated by the Montreux Convention of 1936 and give Russia access to the Mediterranean; 20% and 35% of Russia's crude exports pass through the Turkish and Danish straits respectively.
The Economist modelled optimal routes between 41,387 pairs of ports and estimated the trade along each one. Blocking the Strait of Malacca would force around 21% of global seaborne trade to reroute, adding an additional 1,200km to ships' journeys. But blocking all channels through the Indonesian archipelago—including the Sunda, Lombok and Makassar straits—would affect some 26% of global seaborne trade and require an average detour of 7,800km. Were Gibraltar to become impassable, almost as big a share of maritime traffic would have to take an even bigger detour.
In 2003 Hu Jintao, then China's president, fretted about the "Malacca dilemma": the vulnerability created by 80% of China's oil imports transiting through the strait. China has sought to mitigate this through oil and gas pipelines to Russia and Central Asia and through Myanmar to the Bay of Bengal. Since Xi Jinping's rise to power in 2012, the Belt and Road Initiative has invested in a global logistical network including ports around maritime chokepoints. Since 2013 China has turned several disputed reefs and cays in the South China Sea into military bases. In 2017 it established its first overseas military base in Djibouti. It has also experimented with an Arctic shipping route along Russia's northern coast.
Indonesia, Malaysia, Singapore and Thailand co-operate in patrolling the Malacca Strait against piracy, though what they might do in a conflict is debated. America has looked to India to counterbalance China by helping track Chinese ships and submarines exiting the strait.
Cheap technology has extended the reach of armed groups farther out to sea. The Houthis demonstrated how a militia with drones and missiles could disrupt a major sea-lane for years. Russia's invasion of Ukraine severely disrupted Black Sea grain, oil and commodity flows and underlined the geopolitical clout that control of the Bosporus and Dardanelles confers on Turkey. Attacks on seabed infrastructure—gas pipelines and communications cables—have been carried out in the Baltic Sea, probably by both Ukraine and Russia.
Alfred Thayer Mahan, a 19th-century American naval strategist, regarded the oceans as "a wide common" and argued that global power derived from mastery of the seas. America's first foreign war, in 1801, was fought to defend American shipping from predation by the ruler of what is now Libya. Donald Trump's national security strategy, published in November 2025, affirmed the importance of "preserving freedom of navigation in all crucial sea-lanes", though Trump at one point seemed ready to leave the Strait of Hormuz for others to sort out, saying: "We don't use it. You know, at a certain point it will open itself."
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