More than four years after Russia's full-scale invasion of Ukraine, the Black Sea has become one of the key security zones in Europe. However, there are currently not many warships there, Thomas de Waal, a senior fellow at the Carnegie Institution, told DW. In this regard, he speaks of a paradox.
Limited and specific access
Access to the Black Sea passes through a single, narrow "throat". To reach it, a ship from the Mediterranean must pass through the Dardanelles and Bosphorus straits. At its narrowest point, the Bosphorus is only 700 meters wide. "Whoever controls the Turkish Straits, to some extent, controls trade across the Black Sea and has a huge military advantage," says De Waal.
According to Daria Isachenko, a visiting fellow at the German Institute for International and Security Affairs, Russia also has a special interest in the Black Sea. "For Russia, a strong military position in the Black Sea is not an end in itself, but a means to advance its geopolitical ambitions beyond the region and to strengthen its status as a great power."
The Treaty That Makes Turkey a Guardian
The second part of the equation takes us back 90 years. On July 20, 1936, representatives of a dozen countries gathered in the Swiss city of Montreux to resolve a long-standing question: how and by whom should these vital waterways be governed? They adopted the Montreux Convention, an agreement that effectively restored Turkey's sovereignty over the Dardanelles and Bosphorus after years of international control following the Ottoman Empire's defeat in World War I.
The treaty ensures that in peacetime the straits remain open to passenger and commercial ships - crucial to the important trade route. As for warships, countries in the Black Sea region can pass through the straits relatively freely. However, navies from outside the region are limited in terms of the number of ships, tonnage and length of stay - no more than 21 days in peacetime.
In times of war, the rules become stricter. If Turkey does not participate in the conflict, warships of countries involved in the war are not allowed to pass through the straits - a clause with profound consequences for the region after February 2022. This also explains why NATO does not maintain a permanent presence in the Black Sea, unlike in other seas such as the Mediterranean or the North. "For NATO, Montreux is a constraint. For Turkey, a tool for maintaining balance in the Black Sea".
The war in Ukraine is a test for the Montreux Convention
When Russia began its full-scale invasion of Ukraine in February 2022, the Montreux Convention was put to its most serious test in decades. A few days after the start, Turkey activated Article 19, which prohibits the passage of warships of belligerent states.
In practice, this means that neither Russia nor Ukraine can freely strengthen their naval forces in the Black Sea - with one exception: ships based in the Black Sea can return to their ports. "The Convention and Turkey's policy at the beginning of the war were crucial for Ukraine's survival," says expert De Waal. He claims that this has prevented Russia from expanding its fleet, with "up to 30 Russian ships remaining outside the region". This has helped Ukraine maintain "superiority in the Black Sea".
The treaty also limits the capabilities of Western allies. In 2024, Britain donated two minesweepers to Ukraine, but they cannot enter the Black Sea because Turkey considers them warships. According to De Waal, this shows Turkey's strategy: "Leave the Black Sea to us - we will manage." It is also crucial that all countries respect the convention, although we are currently witnessing a gradual disintegration of the world based on international law.
How NATO is adapting to this situation
"In the Black Sea, Turkey's priorities are Turkey first, NATO then", says De Waal. This is motivating NATO to look for ways to adapt its strategy for the region. Turkey has signaled that it does not want a permanent NATO presence, but it allows support for Romania and Bulgaria.
That is why attention is focused on these two NATO members since 2004. However, some experts are skeptical. "The military capabilities of Bulgaria and Romania are barely enough to defend their own territories," says Romanian analyst Iulian Cifu. Nevertheless, Romania is striving to improve them - one example is the expansion of the "Mihail Kogalniceanu" air base, which is to become the largest NATO base in Europe.
What is the future of the Montreux Convention
According to De Waal, the Montreux Convention is "a rather outdated document", but no one wants to change it because it could open up complicated negotiations with Russia. For Turkey, it is a fundamental treaty related to its sovereignty, security and status. Analyst Chifu believes that the treaty should remain in force during the war, but then it can be reconsidered how it is applied to NATO allies.
The main conclusion, according to De Waal, is clear: "There is no other option but to cooperate with Turkey", which remains the strongest factor in the Black Sea. Over the past 90 years, the Montreux Convention has withstood wars, leaders and generations. And as long as it exists, Turkey will control the entrance to the Black Sea.
Author: Athena Bonner