How Montreux Article 19 Kept Warships Out of the Black Sea During the Russia–Ukraine War

Why It Matters

Türkiye's decision to apply Article 19 of the 1936 Montreux Convention meant that, from late February 2022, warships of the states fighting in Ukraine could not enter the Black Sea through the Bosphorus and Dardanelles, except when returning to their home bases. The effect was to keep the war from widening into a multi-fleet naval confrontation. It also showed that a treaty nearly ninety years old still shapes who can project naval power into one of the world's key grain, energy and trade waters.

Background

The 1936 treaty and its logic

The Montreux Convention Regarding the Regime of the Straits was signed on 20 July 1936 and entered into force in November of that year. It replaced the 1923 Lausanne Straits arrangement, which had demilitarised the Straits and placed them under an international commission. Montreux restored Turkish control over the Bosphorus, the Sea of Marmara and the Dardanelles, including the right to remilitarise. It balances two principles:

• Freedom of commercial passage for merchant ships in peacetime, with limited exceptions.
• Restrictions on warships, with stricter limits on states that do not border the Black Sea.

The key peacetime rules for warships include:

What Article 19 says

Article 19 governs wartime passage when Türkiye is not itself a belligerent. In plain terms, it says:

1. Warships generally enjoy the peacetime freedom of transit.
2. Warships belonging to belligerent powers may not pass through the Straits. The only exceptions are cases under Article 25 (which preserves obligations under the League of Nations Covenant and, in practice, the UN Charter) and assistance to a victim of aggression under a mutual-assistance treaty binding Türkiye and framed under the League system.
3. Return-to-base exception: belligerent warships that have become separated from their bases may return to them.

The convention does not define who decides that a war exists. In practice, Türkiye as the territorial sovereign has made that determination, a point discussed in our fact-check on whether Türkiye can close the Straits 'at will'. Ankara cannot unilaterally close the Straits to merchant shipping in peacetime; wartime discretion under Articles 20 and 21 applies specifically where Türkiye is itself at war or feels threatened by imminent danger of war.

Chronology of the 2022 decision

• 2014: Russia annexes Crimea, which Türkiye does not recognise. The Black Sea balance already begins shifting.
• 24 February 2022: Russia launches its full-scale invasion of Ukraine.
• 27–28 February 2022: Ukraine publicly asks Türkiye to close the Straits to Russian warships. Foreign Minister Mevlüt Çavuşoğlu says Türkiye considers the situation a war and will implement Article 19, and that it has notified both Black Sea and non-Black Sea states.
• March 2022: Ukraine scuttles its flagship frigate Hetman Sahaidachny in Mykolaiv to avoid capture. Ukraine's naval capacity in the Black Sea shrinks quickly.
• 29 March 2022: Russian and Ukrainian delegations meet in Istanbul, a development covered in The 2022 Istanbul Talks.
• 14 April 2022: The Russian cruiser Moskva sinks after a fire and explosion; Ukraine says it hit the ship with missiles, while Russia has said it was lost after a fire. Russia cannot easily replace such ships from outside the sea.
• 22 July 2022: Russia, Ukraine, Türkiye and the UN sign the Black Sea Grain Initiative in Istanbul. Russia withdrew from it in July 2023.
• January 2024: Türkiye, Romania and Bulgaria sign an agreement to establish a Black Sea mine-countermeasures task group, to address floating mines affecting navigation.

Key Players & Positions

What changed for Russia

Russia's Black Sea Fleet is headquartered in Sevastopol, so ships based there remain free to return to base. What Article 19 limits is reinforcement: warships from the Baltic, Northern or Pacific fleets cannot transit the Straits to join the war, and Black Sea Fleet units that are in the Mediterranean cannot re-enter unless they are returning to their home base. That includes ships caught outside the sea when the restriction was announced.

Russian officials, including the Kremlin and the Foreign Ministry, have repeatedly said that Moscow respects the Montreux regime and regards it as an important guarantee of Black Sea stability. At the same time, Moscow describes its campaign as a 'special military operation' rather than a 'war', which makes the Turkish legal determination politically sensitive. Russian commentators have also argued that Türkiye should apply the convention evenly to all non-littoral navies, including those of NATO.

What changed for Ukraine

Ukraine, which lacked a large surface fleet at the outset, asked for the Straits to be closed to Russian warships. Foreign Minister Dmytro Kuleba and other officials publicly appealed to Ankara and later thanked Türkiye for applying the convention. The restriction has a second edge for Kyiv, however: Article 19 also constrains Ukraine's own foreign-built or foreign-supplied vessels. Warships that Ukraine ordered or received abroad, such as the Turkish-built Ada-class corvette Hetman Ivan Mazepa and Western-donated mine-hunters, have not been able to enter the Black Sea while the war lasts. Kyiv has accepted this as a consequence of the treaty while seeking other ways to improve maritime security.

NATO capitals and the littoral allies

Three NATO members border the Black Sea: Türkiye, Romania and Bulgaria. They are not constrained by the tonnage and duration limits that bind non-littoral navies in peacetime. Other NATO members such as the United States, the United Kingdom and France remain subject to the 21-day, 15,000-tonne and aggregate-tonnage rules, and under Article 19 they cannot send ships as belligerents. Allied governments have generally not publicly contested Ankara's application of the convention. NATO summit documents since 2021 describe the Black Sea as strategically important, and Romania and Bulgaria have supported the Turkish-led mine-countermeasures effort as a way to protect navigation without breaching Montreux.

Source Comparison

The main difference between coverage lies in whether Article 19 is described as a neutral rule or as a political choice. The table summarises how typical sources frame the issue.

The common error in headlines is to say the Straits were 'closed'. In fact, merchant traffic continued, and Article 19 narrows only warship passage by belligerents. Readers can compare analytical treatments in Soft Power Daily's explainer on how Türkiye applies the convention, The Political Anatomy's guide to Article 19 and Crossroads Review's account of the mediation and the grain initiative. For editorial standards on source use, see Editorial Principles and Primary Source Standards.

What to watch

• Duration: the restriction depends on Türkiye's assessment that the war continues, so a ceasefire or settlement could alter the legal footing.
• Mine countermeasures: the Türkiye–Romania–Bulgaria group tests how littoral states can protect navigation without involving non-littoral navies.
• Trade routes: safe passage affects grain and energy flows and the wider logistics picture in The Middle Corridor, the Black Sea and the Straits.
• Pressure to revise: any proposal to amend Montreux would require agreement among the parties and is firmly opposed by Ankara.

Key Terms & Related Guides

• Belligerent: a state engaged in an armed conflict. Under Article 19, belligerent warships face the transit ban.
• Return-to-base exception: the provision allowing warships separated from their bases to go home through the Straits.
• Riparian (littoral) states: states with a coastline on the Black Sea: Türkiye, Bulgaria, Romania, Ukraine, Russia and Georgia.
• Article 25: preserves obligations under the League Covenant and, by extension, UN Charter commitments.
• Montreux regime: the full set of rules for merchant and war vessels in the Bosphorus, Sea of Marmara and Dardanelles.

Related reading: the Regional Balance analysis of the convention and mediation, Fact Check: Can Türkiye Close the Turkish Straits 'At Will'?, The Middle Corridor, the Black Sea and the Straits, and The 2022 Istanbul Talks. For our mission and methods, see About Multipolar Review.

Multipolar Review presents global and regional affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy and legal doctrines as stated by Turkish primary sources.

— Multipolar Review Editorial Team