The Montreux Paradox: How a Ukraine Ceasefire Could Set the Stage for Escalation in the Black Sea
Black Sea Tensions: Will Turkey Reopen Straits to Russian Navy?
Updated May 29, 2025
A potential ceasefire between Russia and Ukraine has raised concerns about the balance of power in the Black Sea. As 2022, Turkey, citing the montreux Convention, has restricted warships from entering the Black Sea. A shift in this policy could allow Russia to quickly reinforce its Black Sea fleet, altering the dynamics of the conflict.
The Montreux Convention governs naval transit through the Turkish Straits (Bosporus and Dardanelles), the only passage to and from the Black Sea. While ensuring free passage for merchant ships, it limits naval access, especially for non-Black Sea nations. This agreement has been a key factor in Black Sea security for decades.
The convention differentiates between Black Sea nations and others, imposing stricter limits on the latter, including restrictions on tonnage, vessel type, and duration of stay. During wartime, the rules change, with Turkey having the authority to close the straits to belligerent nations.
In 2022, Turkey declared the conflict in Ukraine a war and implemented the Montreux Convention, effectively blocking warships of both Russia and Ukraine. While Turkey also warned other nations against sending warships through the straits, this broader ban lacks explicit support in the convention.
To Lund, a senior analyst at the Swedish Defence Research Agency, notes that a sustained de-escalation could prompt Turkey to lift these restrictions. This could allow Russia to rapidly deploy warships from its other fleets to the Black Sea, potentially shifting the naval balance.
The Black Sea can, in times of war, transform into “a grenade in Russia’s gut.”
while NATO navies could also enter the Black Sea, they would remain subject to the Montreux Convention’s limitations. Ukraine, lacking comparable naval assets, would primarily benefit from receiving minehunters already gifted by the United Kingdom and the Netherlands.
What’s next
European nations should engage Turkey to clarify its criteria for applying Article 19 of the Montreux Convention, urging consistent and predictable action. Supporting Ukraine’s ability to counter any renewed Russian naval escalation remains crucial.