‘When a rattled statesman confronts a dilemma’, Henry Kissinger wrote, ‘he is sometimes tempted to pursue every course of action simultaneously.’ The dilemma of fighting Iran while it closes the Strait of Hormuz, crossed until recently by 20 per cent of the world’s oil and liquefied natural gas, has made President Donald Trump swing from asking allies and adversaries for help, to stating that no help is needed, and then to declaring that ‘it will re-open itself’, and, finally, to demanding that Iran ‘open the f***in’ straits!’ Chaotic planning, a flirtation with the maximalist goal of regime change and an underestimation of the adversary have come up against one of the world’s most formidable problems: maritime chokepoints.

The challenge and opportunity of the world’s seas and oceans have more often been associated with their vastness; they formed the backdrop to the achievements of Christopher Columbus and Ferdinand Magellan, both of whom traversed great distances in search of treasure, salvation and dominion. But the narrowness of the sea between two protruding points of land has often posed challenges and offered opportunities just as significant as those of distance. To reach the Pacific Ocean from the Atlantic, for instance, Magellan had to navigate his way through a complex and dangerous set of narrow waterways in the extreme south of the Americas, a strait that now bears his name.

When situated at the gateway between busy seas, straits become chokepoints. But it is not just the volume of commercial traffic that lends a chokepoint strategic significance. As the passageway for navies or the connection points of empire, they can be key elements in high-stakes negotiations between great powers, revealing their strengths and weaknesses to each other. A further aspect of their political as opposed to commercial importance is that they can be used to break a stalemate prevailing elsewhere. When used deftly, they can even be an Archimedean point, tilting a world contest in favour of one party or another. As nodes of crisis, they can sometimes prompt leaders to draw the wrong conclusion from one straits incident when dealing with another, with dramatic geopolitical consequences. As if all this were not enough, the competition for control of chokepoints can acquire religious weight or be otherwise motivated by confessional fervour. Perhaps no other geographical feature in the world can combine all these elements within such tightly compressed zones, creating flashpoints for repeated confrontation. Chokepoints truly are the crossroads of history.

In the early 15th century, the Chinese admiral Zheng He visited the small island of Hormuz, located within the strait where the Persian Gulf meets the Arabian Sea, part of the Indian Ocean. It was then ruled by an independent kingdom very close to Iran. He visited as much out of curiosity as commercial ambition, admiring the street acrobats that performed in the city. In general, he used force only sparingly, mostly to protect local allies, and his fleet had offered gifts to Hindu gods and to Allah, thereby honouring both Hinduism and Islam. Though he asserted a notional Chinese sovereignty over Hormuz, the admiral did not return and the Middle Kingdom concerned itself with matters closer to home, including the Strait of Malacca, the main passageway between the Indian Ocean and the South China Sea. China had established a strong commercial presence in Malacca, the city commanding the strait, ruled by a Hindu Rajah named Parameswara, who, according to some chronicles, converted to Islam and became Iskandar Shah. Hindus and Muslims lived side by side with the Chinese settlement in this multi-confessional commercial hub.

Then, in 1498, the Portuguese sailor Vasco da Gama reached Cochin, in India, having rounded the Cape of Good Hope, thereby opening up a new route to the spices and other goods from the East. Da Gama and the Portuguese were about to disrupt the religious and geopolitical equilibrium in and around the Indian Ocean.

Trained for generations in the warrior ethos of the Iberian wars of reconquest, which pitted Christian against Muslim, the Portuguese brought a much a greater readiness for violence and a much less tolerant form of religiosity to the Indian Ocean. In 1507, they tried to take Hormuz. In 1511, under the command of Afonso de Albuquerque, they stormed the city of Malacca. Albuquerque ordered that Hindu houses be left alone and that only Muslim ones could be plundered. Malacca was the key to the spice trade, centred on the islands of Ternate and Tidore, much further east. Albuquerque and his son realised that controlling the trade of the Indian Ocean required command of three chokepoints: Hormuz, Malacca and the opening of the Red Sea, the Bab-al-Mandab Strait, which leads up to Egypt and, beyond that, the Mediterranean.

In 1515, the Portuguese finally took Hormuz, thereby securing the second of the three bases they needed. But their intrusion into the Indian Ocean coincided with the beginning of the apogee of the Ottoman Empire and a long struggle ensued. Albuquerque had already defeated the Egyptian Mamluk fleet at the Battle of Diu in Northwest India in 1509, allowing them to establish the ‘State of India’, which would be centred on Goa. In 1517, they raided Jeddah on the Arabian Peninsula, perilously close to Mecca, the Islamic holy city. The Red Sea combined commercial and crusading imperatives. But that very year the Ottomans captured Jerusalem from the Mamluks and began to consolidate their domains in a southward direction.

The Portuguese seized and retained Hormuz and Malacca, making more money as commercial middlemen between Asian traders than as spice merchants. Yet they failed to secure the entrance to the Red Sea. Opportunity appeared to beckon with the prospect of an alliance with Shi’ite Iran against the Sunni Ottomans, but the crushing victory of the latter against the former at the battle of Chaldiran in 1514 buried the project. Though preoccupied with wars in Europe, the Ottoman Sultan Suleyman the Magnificent, captured Aden, near the mouth of the Red Sea in 1538 and Basra in 1546, in the Persian Gulf, but at the wrong end of it. In 1552, the Ottoman commander Piri Reis was ordered to take the Island of Hormuz from Portugal’s grasp. The attack began well. Ottoman troops landed on the island and surrounded the citadel, but the Portuguese walls proved resistant to Ottoman firepower. Hearing that a Portuguese fleet was on its way, Reis fled to Basra and then to the Red Sea with captured goods, against the orders of the governor of Basra. In 1554 he was beheaded for cowardice.

A string of Portuguese forts now lined the coastline of the narrow passage out of the Gulf. Yet European religious strife altered the status quo in the Indian Ocean for a second time when the Protestant Dutch, fighting for independence from a Catholic Spain that had temporarily absorbed Portugal, began to raid Portuguese possessions around the world, including Brazil and Angola. In 1641 they captured Malacca, ending Portuguese dominance of trade in the region and establishing what would become a formidable empire in Indonesia. A complex interdependence of different seas and their produce began to take shape. The Dutch needed salt to preserve their herring, a staple of their diet and carried out daring raids in the Caribbean to get it. In 1638 the King of Denmark increased the ‘Sound Dues’, tolls for ships passing through the Danish Sound, connecting the North Sea and the Baltic. The angry Swedes and Dutch attacked Denmark and forced it to reverse the policy.

In the course of the 17th century, English sailors began to contest the dominion of the Portuguese and Dutch in the Indian Ocean, just as the Dutch had contested Spain’s command of the Atlantic. The crown of the latter was in dispute in 1700 when Charles II died without issue. Bourbon France recognised Philip of Anjou while Britain and Austria backed Archduke Charles of Austria. Supplying troops and operating in the Mediterranean was difficult when the nearest friendly port was Lisbon, on the Atlantic. Consequently, in August 1704, Admiral George Rooke took Gibraltar in a battle with Bourbon forces. With it, Britain had gained its first great chokepoint and window onto the Mediterranean. A subsequent battle at Málaga that month failed to dislodge them. The Treaty of Utrecht in 1713 confirmed Britain’s new possession. In 1814, it acquired the island of Malta, near a narrow passage between Sicily and Africa. Britain was no longer a guest at the Mediterranean, but its master.

Britain’s global power, and that of what US Secretary of War Pete Hegseth recently described as the ‘Big Bad Royal Navy’, advanced rapidly. The French subjugation of the Netherlands in 1795 allowed the British to operate more freely in the Dutch Indonesian territories. After the fall of Napoleon, a British colonial official, Thomas Stamford Raffles, proposed founding a base in what had been the city of Singapura, ‘the Lion’s teeth’, at the eastern end of the Malacca Straits. Founded in 1819 and grudgingly tolerated by the Dutch (commercially blockaded at times), Singapore flourished into a settlement of 97,000 by the late 19th-century and became a key naval base.

Next, the British set their sights on stamping out what they saw as the scourge of piracy in the Persian Gulf. Beginning with a stunning attack on the Eastern Arabian fort of Ras al-Khaimah in 1819, the East India Company launched a campaign of shock and awe designed to bring the offending Arab tribes to the negotiating table. Their onslaught ultimately succeeded in binding the Eastern Arabian sheikhs, whose raiding activities around the Gulf had been a constant thorn in the British side, to their maritime imperium. By imposing on them a treaty outlawing piracy and plunder, signed in 1820, the British were able to turn a troublesome ‘pirate coast’ into a regulated ‘trucial coast’.

This flurry of empire-building by treaty was combined with colonisation. In 1839, when British marines seized Aden and its hinterland, establishing a firm foothold on the southern Arabian Peninsula, from where they could command the trade routes flowing through the Bab-al-Mandab Strait and those passing between East Africa and India. The pacification of the Persian Gulf and the seizure of Aden were looked on with favour by a British ally, the Sultans of Muscat, themselves in the process of taking control of much of the western side of the Indian Ocean, including Zanzibar.

Taken together, control of Aden, the alliance with Muscat, and the weakness of Iran, which had been defeated by Russia in 1828, secured for Britain two more major chokepoints, Bab-al-Mandab and Hormuz. This was eventually strengthened further by the Anglo-Russian Convention of 1907, which made southern Iran a British sphere of influence. Added to Britain’s naval victories against its European rivals, this meant British dominance on the seas at a global level, even if such dominance never amounted to total control.

Once Britain imposed direct rule on India in 1858, the route to its key possession became an even greater strategic concern. Those travelling from Europe to the Indian Ocean, China and the Far East had to call at Alexandria in Egypt, travel by land to the Red Sea for onward seaborne travel or else round the Cape of Good Hope at the southern tip of Africa. In 1875, British Prime Minister Benjamin Disraeli bought a decisive proportion of Egyptian shares in the Suez Canal, built by the French and opened in 1869. In 1878, Disraeli acquired Cyprus, in the eastern Mediterranean, at the Congress of Berlin. This was followed by the British occupation of Egypt in 1882. Britain had secured its fourth major chokepoint, and had realised the vision of Albuquerque. But unlike the violent Iberian adventurer, British naval power needed more than chokepoints to thrive. For, with the advent of steam, the Royal Navy needed a large number of coaling stations located at ports all over the world.

Britain’s dominion of the seas lacked two other key passageways that it or other powers still coveted. British expeditions to Nicaragua in search of a route for a canal had proved fruitless. It was left to the United States to complete a canal in nearby Panama in 1914, in the aftermath of the 1898 war with Spain that had resulted in possession of the Philippines and Guam in the Pacific and Puerto Rico in the Caribbean. At the start of that war the warship USS Oregon had had sail around Cape Horn, in the far south of the world, in order to reach the Caribbean. The Panama Canal shortened the journey. Control of it was a key military and commercial asset in the western hemisphere and heralded the rise of the United States as a great power.

The second passageway was the Turkish Straits (the Dardanelles and Bosphorus), connecting the Mediterranean to the Black Sea. Despite its precipitous decline and its defeats at the hands of Russia in the 18th and 19th centuries, the Ottoman Empire had retained control of it. The victory of Britain and France in the Crimean War of 1853-56 and Peace of Paris had reaffirmed Ottoman control and neutralised the Black Sea, prohibiting warships on it. Yet Prussia’s victory over France in 1870-71 had seen Russia reassert a defiant measure of control over armed Black Sea navigation.

Religious ambitions were deeply entwined with the Turkish Straits, since the city of Constantinople, spiritual capital of Eastern Orthodoxy, sat on the European side of its shores. Commerce, naval power and religious passion all pointed in the direction of Constantinople. In 1908, that ambition burned in the bosom of the more visionary members of the Russian ruling class, among whom was Alexander Izvolsky, the foreign minister. In September, he was tricked by the Austrian foreign minister, the wily Count Aerhenthal. Izvolsky agreed to the forthcoming Austrian annexation of Bosnia-Herzegovina in exchange for explicit Austrian support among the great powers for future Russian control of the Straits. Austria-Hungary went ahead and annexed the former Ottoman province that autumn without saying a word about the straits to anyone. The resulting crisis brought the empires to brink of war and did more than anything else to cement the lasting enmity that would erupt into world war in 1914.

In the summer of 1914, as the war started, the German battlecruiser Goeben and the light cruiser Breslau were chased by the Royal Navy through the Mediterranean, but managed to escape through the Dardanelles to reach Constantinople, where they became part of the Ottoman navy. Their arrival, celebrated by the German crews singing patriotic songs in front of the Russian embassy, helped bring the Ottomans into the war on the side of the Central Powers. In the spring of 1915, as the war on the Western Front settled into a bloody stalemate, the First Lord of the Admiralty, Winston Churchill, ordered an assault on the Dardanelles, hoping to knock the Ottomans out of the war and thereby alter the course of the whole contest. The navy failed to eliminate the land-based defences and allied troops were pinned down with high losses in the mountainous Turkish interior by able defenders led by Mustafa Kemal, the later founder of modern Turkey.

Just as the Turkish Straits played a role in unleashing the First World War, there is a case to be made (at least in part) for the Mediterranean origins of the second, in which chokepoints were central. In the summer of 1935, Mussolini’s Italy began transporting large numbers of troops and supplies through the British-controlled Suez Canal, to its East African colonies to prepare an attack on Ethiopia, then known as Abyssinia, a member of the League of Nations and one of the few independent African nations. Despite eloquent warnings in September, Britain did not intervene when the invasion began in October. The war shattered the association of states half-heartedly containing the rise of Nazi Germany and brought Italy closer to Hitler, the chief malcontent of the postwar order. In March 1936, Hitler felt strong enough to march into the demilitarised Rhineland, another nail in the coffin of the international order. Britain’s inaction at its Suez chokepoint and alarm about Italy’s unchecked imperial ambitions, seemingly backed by Germany, caused Turkey to instigate the Montreux Convention of July that year, an agreement still in force, which allows Turkey to close its straits to warships in time of war. It has recently prevented Russia from sending ships into the Black Sea against Ukraine.

The Mussolini-Hitler partnership was also strengthened by a chokepoint crisis at the other end of the sea. As the Spanish Civil War broke out in July 1936, General Franco, the rising leader of the nationalist rebels, had his best troops stationed in Spanish Morocco. With the Republican navy controlling the Straits of Gibraltar, there was a risk the rebellion would fail. Less than ten days after the rising began, German transport planes began the biggest military airlift to that date, flying the ‘Army of Africa’ across to southern Spain. Its arrival saved the Nationalist cause and allowed Hitler and Mussolini to jointly sponsor Franco in a long war that weakened the position and credibility of the western European powers.

The Turkish Straits then played the role of reserve trump card in the rushed negotiations between Hitler and Stalin in the summer of 1939, leading to the Molotov-Ribbentrop Pact of 23 August. Determined to invade Poland and having failed to deter the British and French, and to convince the Japanese to form an alliance, Hitler and his foreign minister Ribbentrop were desperate for a deal with Stalin to avoid a two-front war with major powers. Ribbentrop flew to Moscow on 22 August, authorised to offer the Soviets a sphere of influence in Eastern Europe, and, if that failed, he was to throw in the Turkish Straits, which Germany did not control, at the expense of Turkey at some future date. Fortunately, Stalin never asked.

The Cold War brought Chokepoints into new kinds of contest: superpower competition and nuclear diplomacy. In 1956, Egyptian President Gamal Abdel Nasser nationalised the Suez Canal. British Prime Minister Anthony Eden had been foreign secretary in 1935 when Britain allowed Italy to use it unopposed and now saw Nasser as a new Mussolini. Together with France and Israel, Britain invaded Egypt but had to withdraw under pressure from US President Eisenhower, keen to build post-imperial influence with rising new nations. The Suez disaster was a watershed in Britain’s imperial history, the end of its independent power.

Between 1954 and 1958 Eisenhower himself had to deal with Chinese artillery fire across the Taiwan Straits and thus a threat to his ally, Taiwan, refuge of the defeated Chinese nationalists. The conflict could have escalated to full-scale war had Eisenhower heeded some of his senior military advisors, but his own authority as a former general was strong enough to steer the United States away from escalation. On the Chinese Communist side, despite leading a non-nuclear power, in 1958 Mao Tse-Tung brilliantly used the Second Straits Crisis to goad the USSR into a nuclear stand-off with the United States, claiming a propaganda victory when talks with the US resumed via America’s Warsaw embassy, from what Mao saw as a position of strength. Both Churchill and Mao had tried to use straits as Archimedean points in a global contest, the latter succeeding where the former failed.

Now, with war raging in the Middle East, chokepoints are once again in the geopolitical spotlight. As levers of world power and as negotiating currencies freighted with commercial value and infused with religious passion, these accidents of geography are as potent today as they were in 1507 when the Portuguese first arrived at Hormuz.