Ukraine and the fight for freedom of navigation

Notwithstanding the deal signed between the United States and Iran on Sunday, naval blockades are set to remain a ubiquitous feature of our world. From Iran’s three-month stranglehold on the Strait of Hormuz, through grain ships finding their way around Russian mines as they leave Odesa, to the ongoing aggressive – yet supposedly ‘routine’ – patrols by China’s Coast Guard in international waters east of Taiwan, freedom of navigation, one of the foundational tenets of the international system, is being slowly eroded.

Weaponisation of maritime chokepoints is the most significant manifestation of this threat. Unless reversed, the economic and strategic repercussions could be dramatic, and pose systemic risks to the global economy. Instead of trying to dominate the entire international system, revisionist powers now exercise leverage asymmetrically – through control, disruption, and intimidation around critical sea lanes and trade corridors. Maritime pressure has become a major weapon of war.

Freedom of navigation is foundational to international trade, underpinning much of the global economy. The rise of naval blockades does more than just inject new volatility into financial and commodity markets. Together with the return of protectionism and the fraying of WTO’s rules-based trading system, it risks fragmenting global supply chains and leaving the world a significantly poorer place.

It is a principle that has anchored the international order and has been codified into international treaties such as the 1982 United Nations Convention on the Law of the Sea (UNCLOS). Its present decline is not entirely without precedent, but the stakes are higher than ever before. Since 1900, international trade has grown more than threefold as a share of global GDP, making blockades around critical chokepoints vastly more damaging than in the past.

The world’s pre-eminent powers have traditionally provided a backstop against violations – the postwar system built by the United States followed the model developed during the Pax Britannica. This tradition has been revived in recent years by repeated freedom-of-navigation exercises in the South China Sea. As much as 22 per cent of world maritime trade passes through the Strait of Malacca, 21 per cent through the Taiwan Strait, and 16 per cent through the Suez Canal. Acquiescing to a world in which such traffic can be regularly disrupted – and in which control of these arteries becomes a routine instrument of extortion – would be the end of the US-led international system and an existential threat to the global economy.

Iran’s strategy in Hormuz amounted to holding the United States – and the world – hostage by threatening the maritime flow of oil and liquefied natural gas (LNG). At the height of the crisis, roughly 15 per cent of seaborne oil was cut off from the world market, a shock comparable to that of 1973, alongside disruptions to the markets for urea and helium, critical inputs into fertiliser and semiconductor production, respectively.

It would be a mistake to think of modern naval blockades as binary, wartime steps. Iran’s explicit blockade was at the far end of a continuum of measures that constrain freedom of navigation – and many of them are deployed in peacetime. Frequent naval exercises, temporary exclusion zones, acts of sabotage, and outright intimidation all raise the risk to navigation and can dissuade economic actors from using sea lanes that were previously open.

The good news is that the tools to resist this drift already exist, and they are being forged, somewhat improbably, in the Black Sea. Ukraine’s experience – sinking a Russian flagship cruiser with a domestically built missile, keeping its grain corridor open under fire, and turning cheap drones and commercial satellites into instruments of deterrence – offers a template for how countries committed to freedom of navigation can still uphold the principle and deter its violators.

Vladimir Putin’s illegal annexation of Crimea in 2014 has long been read through the prism of Russia’s putative historical and cultural claims. The move, however, was not primarily about the past, nor was it a conventional territorial conflict. It was a deliberate precursor to a campaign of maritime coercion directed against Ukraine. Annexation was followed by thorough militarisation: Russia doubled its military presence on the peninsula and fortified it, while the Black Sea fleet in Sevastopol took on modern, Kalibr-capable submarines and missile corvettes. The ultimate purpose was to render Ukraine’s Black Sea exports non-viable in the moment of conflict that arrived in 2022.

By constructing the Kerch Bridge in 2018, Russia unilaterally limited the size of vessels that could reach Ukrainian ports such as Mariupol and Berdiansk. That same year, Ukraine launched arbitration proceedings against Moscow over persistent blockages and the detention of its naval vessels – even as Russia crept towards the militarisation of ever-larger expanses of the Black Sea and the Sea of Azov. On 25 November 2018, three Ukrainian naval vessels attempting a routine transit through the Kerch Strait were intercepted by Russian forces, which rammed one ship, opened fire, seized all three, and captured twenty-four Ukrainian sailors.

The incident was far more important than a bilateral naval dispute. For the first time in the post-Cold War era, a major power had openly used military force to rewrite the rules of navigation in a strategically important corridor while treating captured sailors as political leverage. Russian military planners wanted to set a precedent: to establish that Russia could selectively control access to international waters and impose costs on anyone who challenged its claims. The international response was largely diplomatic, and although sanctions followed, the practical consequences for Moscow were limited. The lesson Moscow drew was straightforward: maritime coercion works.

That lesson extends well beyond Ukraine. Revisionist powers watch closely how the international community responds to attacks on freedom of navigation, and when coercion produces only limited, temporary costs, it becomes more likely to be repeated elsewhere.

The pattern is now familiar across many regions. In the Black Sea and the Sea of Azov, Russia eventually moved from legal claims and infrastructure projects to naval drills, arbitrary restrictions, deployments, and finally blockade. In the Taiwan Strait and the South China Sea, China relies on exercises, exclusion zones, coast guard operations, and administrative claims to reshape the operating environment without crossing the threshold of declared war. In June this year, China launched coordinated maritime enforcement operations close to Taiwan and harassed commercial ships in international waters, following Japan and the Philippines’ announcement of talks on maritime delimitation in that region.

China’s drills near Taiwan sometimes offer the plausible deniability of routine military exercises, but like the ongoing ‘patrols’, their location is unmistakably coercive, sending a message to Taipei and its partners. In the Strait of Hormuz and the Red Sea, Iran and its proxies have used harassment, seizures, and mining to extract leverage far beyond their immediate neighbourhood.

The sequence thus follows a recognisable progression: legal claims, infrastructure control, administrative restrictions, inspections, military exercises, selective enforcement, and finally the threat or use of force. By the time formal blockades appear, the process is already well advanced. As a result, future threats to freedom of navigation are unlikely to start as wars. More likely, they will be disguised as ‘routine exercises’, ‘administrative measures’, or ‘temporary restrictions’ justified on legalistic grounds.

Conversely, even when explicit blockades end, especially on the terms set by the aggressor, their aftertaste lingers. The details of the US deal with Iran are still murky, but it seems safe to say that some residual uncertainty exists about the demining of the Strait of Hormuz, its formal governance, or future passage fees. Unless resolved promptly and transparently, all of these issues will continue to cast a shadow on the Strait’s use as a shipping lane – as does the simple fact that Tehran, having demonstrated the capability, can restrict navigation again at will.

In fairness, not all revisionist powers look at freedom of navigation through the same lens. China, in particular, has good reasons to hesitate. True, as a rising power it has an interest in reshaping the rules of the international order in its favour, including through unconventional and aggressive means on the seas – periodically rattling Taiwan, the Philippines, and Vietnam. Yet China is also a major beneficiary of the very system that such behaviour erodes. Its economic ascent was made possible by globalisation – itself a by-product of the postwar era of free navigation – and no major economy is more exposed to the chokepoints in question: the overwhelming majority of China’s own trade and energy imports transit the same straits it periodically threatens.

Unless Beijing intends to overhaul its growth model wholesale, it remains one of the largest stakeholders in stable maritime trade. A norm that legitimises coercion at chokepoints is a norm that can be turned against China itself – by the United States, by India, or by anyone else astride the sea lanes on which Chinese prosperity depends. That tension, more than any Western entreaty, may prove the most durable constraint on Beijing’s behaviour.

Still, if such erosion goes unchecked, several risks follow. Maritime coercion may become a normalised instrument of statecraft, with harassment, selective blockades, and mining disguised as exercises becoming routine. Global trade will grow more expensive and less predictable, as higher insurance costs, longer routes, and commodity volatility act as a permanent tax on globalisation. Food, energy, and critical supply chains will become increasingly vulnerable to political manipulation, handing states that control chokepoints leverage far beyond their actual economic or military weight. And every successful act of coercion creates an incentive for repetition: what works in one region will be studied and copied in another.

The response must be faster and more effective than existing mechanisms allow. Two pillars have underpinned freedom of navigation since 1945, and both have weakened. The first, arguably more important, was US hard power and the expectation that Washington would reopen closed sea lanes and punish violators. The second was the multilateral system, which offers binding arbitration and authorisations for the use of force against transgressors.

International law has had its blind spots. For example, UNCLOS allows countries to close territorial seas to foreign navigation ‘temporarily’ during naval exercises – a carve-out that has been frequently invoked by Russia and China – without imposing any time or geographic limits on this prerogative. Moreover, the UN is too slow, divided, and veto-constrained to respond effectively. At the same time, political and fiscal constraints in the United States suggest that Washington may be neither willing nor able to play global policeman indefinitely – a doubt underscored by the less-than-straightforward reopening of Hormuz.

Enforcement, therefore, will become more localised, resting on coalitions of the willing rather than on international institutions. Such coalitions may include the United States, which remains a formidable naval power. They may also proceed without it in regions that Washington does not treat as a priority. They will also rely less on conventional naval assets and more on new technological enablers – above all, visibility from orbit. Commercial satellite imagery and military-grade capabilities together impose a new degree of maritime transparency, which is itself a deterrent. Paired with AI, the movement of surface vessels becomes eminently trackable, easing both the detection of military build-ups that precede blockades and the policing of the ‘shadow fleets’ through which sanctions are evaded.

Ukraine has already shown what this looks like in practice. For decades, naval power was measured in ever larger and more expensive platforms. Few examples illustrate that logic better than the fate of Soviet Slava-class cruisers – four of them built in Mykolaiv, in Ukraine, during the Cold War as ‘carrier-killers’ designed to challenge NATO fleets. One of them, later renamed the Moskva, became the flagship of Russia’s Black Sea fleet. In April 2022, it was sunk by Ukrainian Neptune anti-ship missiles. The threat posed by Ukrainian drones and missile strikes has prompted Russia to withdraw the Black Sea fleet from its traditional home in Crimea into Novorossiysk, effectively neutering it as a fighting force.

Maritime dominance, therefore, can no longer be measured by the size and cost of fleets. Precision weapons, autonomous systems, commercial satellite intelligence, and distributed networks increasingly allow smaller actors to impose real costs on larger ones. That is a double-edged sword. On the one hand, it lowers the barriers to entry into the maritime coercion business so that even relatively minor powers and non-state actors can effectively inflict pain on much bigger players. On the other hand, it also gives smaller actors committed to the status quo tools with which they can deter such behaviour.

Ukraine has kept a working grain corridor open under sustained threat, turned maritime drones into instruments of coastal denial, and demonstrated a model of distributed resilience that Western planners would do well to study. Future investment in maritime security should flow not only to traditional naval assets but to anti-blockade capabilities, maritime drones, coastal strike systems, mine-countermeasure technologies, and integrated satellite surveillance.

A number of practical lessons emerge from Ukraine’s experience. Certain acts – mining international sea lanes, attacking or seizing commercial vessels, imposing unlawful blockades – should trigger pre-agreed sanctions, insurance restrictions, and financial measures within days rather than months. Maritime nations should build permanent transparency networks that fuse commercial imagery, military surveillance, and shared intelligence. Flexible coalitions should stand ready to support mine-clearing, escort commercial shipping, and stabilise insurance markets in moments of turbulence. The underlying principle is simple: if maritime coercion is cheap, it will spread; if it is costly, it can be deterred.

Countries that depend on maritime trade have reached a fork in the road. If they continue to take freedom of navigation for granted – putting their trust in multilateral machinery or America’s omnipresence on the world’s oceans – they risk normalising coercive blockades and the weaponisation of shipping. In that world, trade becomes more insecure and more costly, fragmenting into less efficient forms; expensive overland alternatives requiring vast upfront investment, such as the Middle Corridor across Central Asia, would be needed to partly substitute for sea routes that can no longer be trusted. This rollback of one of globalisation’s central achievements would weigh on incomes and prosperity in the developed and developing worlds alike.

None of this is inevitable. The pressure on maritime trade is real and will exact a toll relative to a counterfactual in which the globalised system simply continues to hum along. But those with an interest in preserving its benefits against the depredations of revisionist regimes and predatory non-state actors are not helpless. Key maritime nations should already be building monitoring systems backed by shared satellite and AI capabilities; designing mechanisms to stabilise insurance markets in periods of geopolitical turbulence; committing to automatic sanctions triggered by coercive maritime behaviour; and, in the most sensitive regions, planning jointly for mine-clearing operations and the escort of commercial ships.

The world now coming into view will be less stable than one in which the UN or the United States reliably supplied protection as a global public good. Maritime trade will be threatened more often, and the costs will be real. But new maritime coalitions, more resilient logistics, an integrated maritime-and-space security architecture, and more flexible models of deterrence may be just enough to spare the world the worst of this new era – provided democracies learn to recognise the early stages of maritime coercion and to respond before new blockades fully materialise.