Montreux Article 19 and the Black Sea: How Türkiye Closed the Straits to Belligerent Warships

Why It Matters

Under Article 19 of the 1936 Montreux Convention, when a war is under way and Türkiye is not a party to it, warships of the belligerent states may not pass through the Bosphorus and the Dardanelles, apart from a few narrow exceptions. In February 2022 Ankara announced that it would apply this regime to the Russia–Ukraine war, which kept the war's naval dimension largely inside the Black Sea. The decision shows how a 90-year-old treaty still shapes European security, grain trade and the room for diplomacy.

Background

What the Montreux regime says

The Montreux Convention Regarding the Regime of the Straits was signed on 20 July 1936 and entered into force on 9 November 1936. It replaced the demilitarized, internationally supervised arrangement of the 1923 Lausanne Straits Convention and restored Turkish control over the Dardanelles, the Sea of Marmara and the Bosphorus, together known as the Turkish Straits. Its logic rests on two tracks.

• Merchant ships: In peacetime, commercial vessels of all flags enjoy freedom of transit and navigation (Article 2). The convention also protects merchant passage in wartime when Türkiye is not a belligerent (Article 4).
• Warships: Passage is regulated by detailed rules in Articles 8 to 22. The rules favor states with a Black Sea coastline (riparian states) over outside powers.

Peacetime limits on warships

Aircraft carriers are excluded from passage under the convention's classifications. In practice, ships that blur the category have long been the subject of interpretive disputes.

Wartime: Articles 19, 20 and 21

The convention distinguishes three wartime situations.

• Türkiye not a belligerent (Article 19): Warships generally enjoy transit under the peacetime conditions, but vessels of belligerent powers may not pass. The text lists exceptions for cases arising under Article 25 and for assistance to a victim of aggression under a qualifying mutual-assistance treaty originally framed within the League of Nations Covenant. A further provision allows belligerent warships separated from their bases to return to them.
• Türkiye a belligerent (Article 20): The passage of warships is left entirely to Türkiye's discretion.
• Türkiye threatened by imminent danger of war (Article 21): Ankara may apply Article 20 and must notify the other parties.

The determination that a state of war exists is made by Türkiye under the convention. No formal declaration of war between the belligerents is required for the regime to be engaged, which matters because Moscow describes its invasion of Ukraine as a 'special military operation' rather than a war.

Timeline of the 2022 implementation

Turkish officials said that transit requests from several states were declined, while ships returning to registered home bases remained eligible under the exception. Ankara has not published a full list of requests, so independent verification of individual cases is limited.

Key Players & Positions

Ukraine. Ukrainian officials, including Foreign Minister Dmytro Kuleba on 26 February 2022, urged Türkiye to close the Straits to Russian warships. Kyiv welcomed the Turkish decision. Some Ukrainian officials and outside analysts have argued that the return-to-base clause could in principle be stretched to reinforce the Black Sea Fleet.

Russia. Moscow says it respects the convention and has presented the return-to-base provision as a legitimate right. Russian officials also criticize what they see as a growing NATO naval presence around the Black Sea. Because Russia calls the conflict a 'special military operation', its public framing differs from the Turkish legal determination that a state of war exists under the convention.

NATO members and allies. NATO officials, including Secretary General Jens Stoltenberg, have repeatedly noted that the convention is a binding treaty that Türkiye applies as the Straits' custodian. Romania and Bulgaria, the other NATO littoral states, have focused on maritime security in their own waters. Their cooperation with Türkiye on mine clearance in the western Black Sea is framed by all three as a regional safety measure rather than an alliance deployment.

Other Black Sea states. Georgia, Romania and Bulgaria have called for stronger maritime security and for the free navigation of commercial traffic. Each speaks in the terms of its own foreign ministry, and none has asked for the convention to be revised.

Non-riparian powers. Western naval powers have limited their Black Sea presence because the convention's tonnage and 21-day limits apply to them in peacetime and its wartime rules apply to them in practice. Some policy commentators in these states have asked whether the convention should be updated. No party to the convention has formally proposed a revision.

Source Comparison

Analysts disagree about how much the closure changed the military balance. Many point out that the Black Sea Fleet was already largely in the Black Sea by February 2022, and that the practical effect lay in preventing reinforcement and in limiting NATO ships through the peacetime tonnage rules. Turkish sources respond that the point of the regime is to prevent a regional war from widening into a Black Sea naval war, and that it is applied identically to all. Readers should compare the treaty text, the Turkish Foreign Ministry's statements and the statements of Russia, Ukraine and NATO directly. See also our Editorial Principles for how we separate fact from position.

Sister publications offer complementary explainers: Soft Power Daily on Montreux and Black Sea security, The Political Anatomy on Turkish Straits and Article 19, The Global Anatomy on mediation and the grain initiative and Regional Balance on Türkiye's mediation.

Key Terms & Related Guides

• Turkish Straits: The Bosphorus, the Sea of Marmara and the Dardanelles, governed by Montreux.
• Riparian (littoral) state: A state with a Black Sea coastline: Türkiye, Bulgaria, Romania, Ukraine, Russia and Georgia.
• Belligerent: A state party to an armed conflict. Article 19 restricts its warships when Türkiye is not itself a belligerent.
• Return-to-base exception: The provision that allows belligerent warships separated from their bases to return to them.
• Aggregate tonnage: The cumulative limit (30,000 tons, up to 45,000 under conditions) on non-Black Sea warships in the Black Sea (Article 18).
• Joint Coordination Centre: The Istanbul body that supervised ship inspections under the Black Sea Grain Initiative.

Related guides on this site:

• Türkiye's Strategic Meridian: How Geography Shapes Grand Strategy from the Mediterranean to the Caucasus
• Three Seas, One Coastline: Türkiye's Maritime Jurisdiction in the Aegean, Black Sea and Mediterranean
• From Euphrates Shield to Spring Shield: How Türkiye Built a Security Belt Along Its Southern Border
• About The Strategic Meridian: Mission, Perspective and Transparency

This analysis is published by The Strategic Meridian Editorial Team. The Strategic Meridian is an editorial publication that presents analysis from a Türkiye-informed perspective on regional security, maritime law and history. Claims are attributed to primary sources such as treaties, UN documents, official archives and legal texts, and readers are encouraged to consult them directly. The section marked 'Türkiye's Strategic Doctrine' reflects official Turkish policy as stated by Turkish government sources.