In March 2026, the world watched, stupefied, as soaring oil prices upended global financial markets. The International Energy Agency warned of the largest supply disruption to the global oil market in history, as crude flows through the Strait of Hormuz plunged to a near standstill after US and Israeli attacks on Iran at the end of February. Iran flaunted its stranglehold over the world economy, which will be heading towards a global recession should the current disruption persist. The impasse along the 39-kilometre maritime chokepoint triggered a succession of ensuing blows to the fracturing world order: US sanctions on Russian oil were lifted; China rebuffed US summons to send warships to safeguard the vital waterway; Germany and the UK also refused to send a contingent, despite President Trump’s menacing threat of a ‘very bad future’ for NATO.
The havoc that has been unleashed along the Strait of Hormuz – which should have been foreseen – has demonstrated that maritime chokepoints, upon which international commerce depend, remain the global economy’s Achilles’ heel. How, then, might maritime chokepoints be effectively governed, even during wartime?
One answer can be found by venturing outside the Persian Gulf. Look northwest from Iran and towards the entrance of the Black Sea. There lies another wartime maritime chokepoint, the Turkish Straits. It is something of a diplomatic triumph that this waterway has barely featured in discussions of the Russo-Ukrainian conflict over the past four years. Rather, even amid conflict, the Straits have continued to allow commercial shipping for Black Sea grain exports, albeit at a lower capacity. This is because of a little known, but longstanding achievement of international diplomacy: the Montreux Convention, forged in 1936, which continues to govern the chokepoint. In the early days of the war in Ukraine, Turkey invoked Article 19 of the self-executing Convention to close the Straits to all warships. Unlike the Strait of Hormuz, thanks to Montreux, the Turkish Straits have subsequently remained out of wartime headlines.
Wartime disruption to the Turkish Straits could choke off a third of global grain and fertiliser supplies if the narrow neck were to be left in a state of war and anarchy, akin to where the Strait of Hormuz now finds itself. Comprising the Dardanelles and the Bosporus, the Turkish Straits form the only gateway between the Black Sea and the Mediterranean Sea. As a vital nexus between Europe, Asia, and North Africa, the Straits have been the subject of fierce political rivalry since antiquity, from the Greeks to the Byzantines, from Ottoman sultans to Russian tsars. Regulation of the Straits – the crux of the ‘Eastern Question’ that drove so much European diplomacy in the long 19th century – was brought to the fore after the First World War and the ultimate demise of the Ottoman Empire. In 1936, the Montreux Convention’s ratification proved an enduring victory in its construction of a maritime chokepoint regime. In the following nine decades, the Straits emerged from all hostilities relatively unscathed, even during the war in Ukraine.
Lessons from centuries of volatility in the Turkish Straits highlight what did not work in maritime chokepoint governance: first, the dominance of a revisionist power, such as the Russian Empire, at the expense of other great powers; second, sole reliance on a loose framework of internationalisation, which doomed Montreux’s immediate precursor, the Lausanne Convention. History also sheds light on what fared well for the Straits: critically, the responsible party must be a status quo power, and the arrangement must also suit the material interests of all the major great powers. Even a single great power harbouring grievances over the regime would severely disrupt the chokepoint’s stability.
Lowering the risks surrounding a maritime chokepoint is crucial to preventing marine insurance bills from skyrocketing in a time of war. It is therefore necessary that the arrangement is managed by a status quo power which exhibits strength and firmness. Turkey suits the criteria perfectly, bolstered by the second-largest standing army of NATO.
All does not bode well, however, for the Strait of Hormuz, which is strangled by the revisionist Iranian regime. The current situation there only highlights the futility of appeals to the United Nations Convention on the Law of the Sea (UNCLOS). Iran need not attack a large number of tankers to haunt shipping companies and insurance underwriters for an extended period after hostilities subside. While the resumption of oil-flows suits the material interests of all powers – except, perhaps, for Putin’s Russia – decades of brittle trust in the region make the establishment of a Montreux-like framework in the Strait of Hormuz implausible in the foreseeable future.
Dire short-term prospects for Hormuz notwithstanding, the successful Montreux regime still provides a pertinent framework for chokepoint management should the Persian Gulf become more stable again in the future. Consider the unique political landscape in July 1936, when European statesmen gathered in the picturesque lakeside town of Montreux, Switzerland: Hitler had consolidated power in 1934; Mussolini’s Italy had invaded Abyssinia in October 1935; and Germany had remilitarised the Rhineland in March 1936. The collective security provision of the League of Nations had been visibly crumbling. For the newly established Turkish Republic under Mustafa Kemal Atatürk, inability to secure sovereignty over the entrance to the Black Sea was existentially threatening. More importantly, Kemalism championed the status quo, as per Atatürk’s adage, ‘peace at home, peace in the world’. Turkish lobbying to nationalise the Straits was thus largely palatable for those presiding at the Palais Wilson.
In the current Hormuz crisis, India has proposed a diplomatic solution to safeguard the waterway. Yet the diplomatic obstacles to negotiating a Montreux-like framework for Hormuz should not be underestimated. Indeed, the 1936 settlement involved balancing precarious tensions between London, Berlin and Moscow. In German eyes, the Soviet Union could be interpreted as a beneficiary of Montreux: Turkey could credibly close the Dardanelles during wartime to the benefit of Moscow, as Russian warships also gained navigation privileges. Disgruntled by this idea, Germany threatened to increase the size of her fleet and warned of Turkish subjugation to Russian influence in the region.
Anthony Eden, then British Foreign Secretary, challenged the German proposition, pointing out that Russia would never willingly delegate defence of the Black Sea to a long-time adversary. Eden’s intervention, however, did not express a charitable feeling towards the Turks in London. Rather, it conveniently suited British commercial interests to allow a Turkish-controlled chokepoint regime to stymie German and Soviet ambitions. Safeguarding routes to India had shaped major moves in British foreign policy since the 19th century. Alongside the Suez Canal, the Turkish Straits represented a significant avenue for British trade and a major geopolitical concern. British shipping consistently accounted for more than 20 per cent of total annual tonnage transiting through the Turkish Straits, peaking at 26.8 percent in 1938. A stable Straits regime and cordial relations with Ankara were therefore essential to sustaining British commercial predominance.
Ultimately, Montreux placed the Straits under sovereign Turkish control. It also detailed distinctive stipulations of tonnage, duration of stay, and advanced notice for merchant and military vessels, with preferential treatment to Black Sea littoral states. It is the clarity and precision on Turkey’s wartime discretionary power in Montreux that have safeguarded the chokepoint’s stability for nine decades since its establishment.
The ongoing war in Ukraine was not the most perilous pressure test of the Montreux Convention’s resilience to date. During the Cold War, the Soviet Union pressed for a revision of Montreux in a bid to secure more privileged access to the Black Sea. What Stalin envisaged would have given the USSR quasi-sovereignty in the wider Black Sea region and a treaty-friendship with Turkey modelled after Poland and other Communist satellites in Eastern Europe. This plan, first proposed at the Yalta Conference, made Churchill distinctly anxious. It was at this point that the fledgling Cold War contest between the United States and the Soviet Union began to work to Turkey’s benefit. Despite initial ambivalence, Washington interpreted the Soviets’ browbeating of Turkey as a broader push for predominance in the Eastern Mediterranean. Fearing an upset to the balance of power in Europe, the US and Britain aligned their backing of Turkey to maintain the Montreux regime and contain Soviet adventurism.
Subsequently, the United States adopted a containment policy from 1947, enacted the Marshall Plan in 1948, and welcomed Turkey as a member to NATO in 1952. Turkey’s accession into NATO was momentous, since Turkey provided a buttress against Russian expansion on the alliance’s southeastern flank. Consequently, the Turkish Straits also became protected by NATO’s Article V collective security commitments.
The crucial lesson of Montreux – that a chokepoint should be controlled by a dependable status quo power – cannot be applied to Hormuz under the current circumstances; achieving such an arrangement would require complete Iranian capitulation and a permanent US military presence. This is because the Montreux Convention is a framework built upon trust and reassurance rather than coercion. Iran now knows that choking off the Strait of Hormuz is a reliably potent weapon that it can use again in the future; and the Islamic Republic is unlikely to give up such lethal leverage over its militarily superior adversaries without sufficient evidence that this bargaining chip will no longer be effective. If a future Hormuz regime could ever be institutionalised in the style of Montreux, then rebuilding trust will be essential to its preservation. It will require a strong, reliable status quo power with credible military presence as the gatekeeper.
Any treaty arrangement must also command international buy-in, and serve as a mariage de convenance to all relevant powers. The young Turkish Republic, then seeking to join the club of status quo powers, enjoyed these attributes in 1936. The future stability of the Strait of Hormuz will first depend upon a slow restoration of mutual confidence between Iran and its adversaries. After nearly five decades of confrontation, building on whatever brittle trust remains will not be a simple task.
