This essay is excerpted from “Reprioritizing the Black Sea after the War in Ukraine,” a publication of the Hoover History Lab. Download the report here.
Ironically titled the “Pontus Euxinus” (“hospitable sea”), the Black Sea has been a battleground for maritime dominance since antiquity. Its sole entrance, the Turkish Straits, facilitates over 20 percent of the global wheat trade and safeguards the stability of the greater Black Sea region. Between the late seventeenth century and 1936, the Straits’ legal regime shifted on average every seventeen years, with fourteen separate ratified treaties; the Russian Empire was the main instigator of such instability, benefiting from all negotiations unfavorable to the Ottoman government.
While focused on the Gulf of Finland and the Danish Straits, Russia saw access to warm-water ports on the Black Sea coast and unhindered passage through the Turkish Straits as increasingly indispensable. During the years 1762–96, when Catherine the Great reigned, Russia’s yearning for ascendancy over the Black Sea became ingrained in Russia’s imperial identity.
It is also with Catherine’s glory and legacy that Vladimir Putin purportedly most resonates.
War has once again engulfed the Black Sea region, commencing with Russia’s attack on the sovereign territory of Ukraine in February 2022. Yet the sea itself has figured far less than the land around it in the battle space. Why? The 1936 Montreux Convention, forged from great-power rivalry and Turkey’s balancing diplomacy, has safeguarded the Black Sea for nearly a century. In March 2022, Ankara’s invocation of Article 19 of the Convention—closing the Straits to all warships, both belligerent and nonbelligerent—successfully limited the naval theater of the war against Ukraine, proving that the framework under Turkish sovereignty serves as a stable bulwark against Russian aggression and wider conflict.
But preserving the status quo after the war will require renewed strategic attention, because Russia’s ambitions will not fade even with a cease-fire (which is not yet on the horizon). What could the United States, the European Union, and other interested parties do to diminish the Black Sea as a locus of hostilities and enhance its role as a nexus of trade and cooperation?
Whose “lake”?
Historical precedent and Moscow’s current Maritime Doctrine (in which the Black Sea is effectively viewed as a domestic Russian lake) suggest that Russia’s appetite for the Black Sea and the region’s geopolitical vulnerability are perennial problems that cannot be resolved with a peace plan in Ukraine. Russia will continue to view it as an internal lake, and Moscow’s quest for access to warm-water ports will remain a vital national interest. Once the Turkish Straits are reopened after the signing of a cease-fire, the Black Sea will be exposed to Russian advances toward its north coast. It is thus crucial that policymakers across the Atlantic anticipate the region’s potential postwar instability.
Centuries before NATO was set up, Russian rulers viewed the Black Sea as a vital sphere of influence and a gateway to imperial expansion, annexing the Crimean Khanate and establishing the Russian Black Sea Fleet in Sevastopol. European powers later watched quietly as Russia negotiated the rights to close the Straits at her discretion. Even considerable territorial concessions through European diplomatic efforts failed to restrain Russian advances toward the north coast of the Black Sea. Each time Russian influence expanded unopposed, the European balance of power was shattered.
In 2026, there is little reason to expect any fundamental changes in Russia’s objectives and diplomatic conduct. Regarding the Black Sea region, demands perpetuating Russian dominance will be reiterated until accepted, or rather, capitulated to. Policymakers must prepare for continued Russian rigidity and refusal to negotiate.
Russian restraint and setbacks in the Black Sea, including Turkey’s accession to NATO and the formation of the Montreux Convention, emerged from the presence of competing great-power rivalries. When Russian aggrandizement was growing unchecked in the East Mediterranean, it was the rise of Britain and her Royal Navy that eventually stalled Russian advances, neutralizing the Black Sea after the mid-nineteenth-century Crimean War. The Montreux Convention, the current legal regime safeguarding the region, was also forged by great-power rivalry. Conflicting priorities among the UK, the Soviet Union, and Germany led to the production of a compromise, of which Turkey was the beneficiary.
In 2026, even though few nonlittoral great powers are as deeply invested in the Black Sea as Russia, great-power rivalry can still effectively undermine Russian advances toward the region.
Today, the pragmatic relationship between Ankara and Moscow is still central to the global balance of power, but European allies must be wary of the utilitarian understanding between the regimes of Turkish President Erdoğan and Putin. The key to Montreux’s success in 1936 lay in the balancing diplomacy adopted under the leadership of Mustafa Kemal Atatürk, who championed national sovereignty and the preservation of the status quo. Given the natural rivalry between the two powers over the Black Sea, any ostensible understanding between Ankara and Moscow today is inevitably more delicate and transactional than publicly exhibited. The end of today’s war in Ukraine will once again threaten to jeopardize that transactional relationship.
For the postwar Black Sea order, the durability of Montreux underscores the importance of an unambiguous legal framework with a trusted ally, as it effectively extends NATO’s control and security protection to the maritime choke point. Montreux’s clarity provided a robust framework for Turkey’s resilience.
Advances in modern surveillance and precision weaponry have further enhanced Montreux’s political relevance. The balance of military power in the Black Sea has decisively shifted shoreward and no longer rides on the naval assets at sea. The Royal Navy learned this lesson in the Dardanelles campaign in the First World War, when it found itself unable to force a passage through the Straits. The lesson from military history endures today: ships cannot fight forts.
The coastline of the Black Sea is fully lined with mobile launchers, and Ukraine’s sinking of the Russian cruiser Moskva in the early stages of the war would be the fate of any warship that tried to navigate the constricted waters under satellite and drone surveillance.
“Russians, after all, do not change”
Because Russia has never regarded the Black Sea as peripheral, the region has always been and will continue to be a core theater of Russian national prestige and strategy. The reasons for renewed Western prioritization of the region are manifold: persisting Russian territorial ambitions; the rising significance of the Middle Corridor and the potential for Sino-Russian disruption on the trade route; fragility of the transactional Russo-Turkish rapport after the war in Ukraine; and NATO’s Article 5 security commitments. Turkey’s 1952 move to NATO transformed the nature of the Straits question: Instead of being an isolated regional issue, Turkey’s sovereignty over the Straits could potentially trigger a general conflict that involves Russia, Western Europe, and the United States.
As soon as the Straits reopen, Russia will be able to redeploy naval assets from its Northern, Baltic, or Pacific fleets to reinforce the Black Sea Fleet. Then, as a littoral power of the Black Sea, Russia is well positioned to deploy gray-zone tactics to disrupt commerce and regional stability.
The present settlement of nearly nine decades, albeit the most enduring by far, is not immune to change. The case for caution remains convincing.
Preserving the status quo after the war in Ukraine will require renewed strategic attention. Attesting to persistent Russian hubris toward the Black Sea and the Straits, the British ambassador to Turkey during the 1936 negotiation of Montreux, Sir Percy Loraine, articulated the reason for continued alert:
The Russians, after all, do not change. In the days of the Tsar, their eyes were constantly fixed upon Constantinople. The new Tsar (Stalin) works in a different way. He makes a military alliance with Turkey; he becomes indispensable to Turkey, or so he believes; he encourages the fortification of the Straits; he endows Turkey with certain industries; he obtains a privileged position, generally, in this country. How far will this movement proceed?
Now in 2026, as the war in Ukraine enters its fifth year, the Black Sea region’s future stability rests squarely on Western powers’ resolve to elevate the region beyond a peripheral concern.
