Montreux Article 19 in Practice: How Türkiye Applied the Straits Rules for Belligerent Warships in the Black Sea War

Why It Matters

Can Türkiye close the Straits? Only in a limited, treaty-defined sense. Under Article 19 of the 1936 Montreux Convention, Türkiye, as a non-belligerent, may refuse passage to warships of states at war, except for ships returning to their bases and a few League of Nations Covenant-related cases. It cannot lawfully stop merchant shipping, and it has no general right to shut the Bosphorus and Dardanelles to everyone.

Since February 2022 that distinction has shaped Black Sea naval dynamics. Ankara says it applied the text evenly to both sides in the Russia–Ukraine war, while Moscow, Kyiv and outside analysts each read the results differently.

Background

What the convention says

The Convention Regarding the Regime of the Straits was signed in Montreux on 20 July 1936 and entered into force on 9 November 1936. It replaced the demilitarized Straits regime of the 1923 Lausanne arrangements and restored Turkish control and fortification of the Straits. The original signatories were Bulgaria, France, Greece, Japan, Romania, Türkiye, the United Kingdom, the Soviet Union, Yugoslavia and Australia. Russia continues the Soviet seat in this regime. Ukraine is not a signatory.

The regime works in layers:

• Peacetime, merchant ships: freedom of transit and navigation by day or night, under any flag, subject to sanitary and navigation rules (Articles 1–2).
• Peacetime, warships: Black Sea states enjoy broader rights. Non-Black Sea states face notification requirements (generally eight days, with fifteen days advised for non-littoral states), limits on tonnage and number of ships, and a maximum stay in the Black Sea of 21 days (Articles 10–18).
• Wartime, Türkiye not belligerent: merchant vessels keep freedom of transit (Article 4). Warship passage is governed by Article 19.
• Wartime, Türkiye belligerent or threatened with imminent danger of war: Ankara gains wide discretion over warship passage (Articles 20 and 21).

What Article 19 provides

In plain terms, Article 19 says that when Türkiye is not at war, warships keep passage rights on the peacetime terms of Articles 10–18. Warships of belligerent powers, however, may not pass, with these exceptions:

1. Covenant cases: actions arising from the League of Nations Covenant, and assistance to a victim of aggression under a registered mutual-assistance treaty binding Türkiye. These were drafted for the League era and have had little practical use since 1945.
2. Return to base: belligerent warships that have become separated from their bases may return to them.
3. No hostile acts in the Straits: belligerent warships may not capture vessels, exercise visit and search, or carry out any hostile act in the Straits.

The return-to-base clause is the provision most often debated in 2022 and after, because it preserves the ability of a belligerent's ships to go home even in wartime.

Earlier tests

Montreux has been stress-tested before. During the 2008 Russia–Georgia war, questions about the tonnage limits for non-Black Sea navies surfaced when the United States considered sending large hospital ships. The convention's detailed rules, particularly on aggregate tonnage, have been a recurring point in Black Sea politics. Analyses of these mechanics appear in sister publications such as The Political Anatomy's explainer on Article 19 and Black Sea security and Soft Power Daily's overview of the convention and Black Sea security.

Chronology, 2022 onward

Exact figures for individual refused transits have been reported variably, so this article does not cite them.

Key Players & Positions

Türkiye (guardian and non-belligerent party). Ankara presents itself as the implementer, not a party to the conflict. It has said that it applies the convention to all belligerents, Black Sea and non-Black Sea, and that the aim is to keep the war from spreading into the Black Sea. Its statements run through the Ministry of Foreign Affairs and the Presidency.

Ukraine (non-party but directly affected). Kyiv, through its foreign ministry and diplomats, asked Ankara to block Russian warships. Ukrainian officials have also argued that the return-to-base exemption should be read narrowly so that it does not allow the Russian fleet to be reinforced or rotated. Ukraine has also sought naval support from partners, which Article 19 constrains.

Russia (convention successor to the Soviet signatory). Moscow has generally said it respects Montreux as the governing framework and objects to any move to revise it. Russian commentary has stressed that Article 19 itself protects the right of ships to return to base. Russia also benefits from the tonnage and stay limits that restrict non-Black Sea navies' presence near its Black Sea coast.

Western states and NATO allies. Non-littoral NATO members operate under the 21-day stay and tonnage caps. Their governments have publicly respected the regime. Some Western analysts argue that Montreux, designed for a different era, gives littoral states, including Russia, a structural advantage in the Black Sea.

Other Black Sea littoral states. Bulgaria, Romania and Georgia, besides Türkiye, Russia and Ukraine, have security interests in how the regime is applied. Montreux also touches their ability to host allied naval presence.

Source Comparison

Two cautions apply when reading coverage. First, headlines often say Türkiye 'closed the Straits', which overstates the legal effect: merchant shipping continued and only belligerent warships were restricted. Second, analyses diverge on how much practical difference the closure made, since Russia's Black Sea Fleet was already largely inside the sea. For comparable explainers, see The Global Anatomy on Montreux and Türkiye's mediation and Bloc Politics on how Türkiye governs the Straits. Our approach to separating fact from position is set out in Editorial Principles.

Key Terms & Related Guides

• Belligerent: a state party to an armed conflict. Article 19 applies to warships of belligerent powers.
• Return-to-base exception: the Article 19 provision that lets belligerent warships separated from their bases return to them.
• Non-littoral (non-Black Sea) power: a state without a Black Sea coast. Its naval transit is limited by tonnage, number and a 21-day maximum stay.
• Article 20 / 21: the provisions giving Türkiye broader discretion when it is at war or threatened by imminent war.
• Turkish Straits: the Bosphorus, Sea of Marmara and Dardanelles, the only maritime route between the Black Sea and the Mediterranean.

Related reading: The Blue Homeland Doctrine Under Review for Türkiye's maritime legal reasoning, and About Diplo Review for our mission and transparency policy.

Diplo Review presents Türkiye's official perspective on the issues it covers, grounded in treaty texts, UN documents, and Ottoman and Turkish state archives. Primary sources are cited and linked wherever possible so that readers can verify claims and form their own judgments.

By the Diplo Review Editorial Team.